Hey, Andrey.
while investigating some memory management problems I've got the logdep splat below.
Looks like something is wrong with drm_sched_entity_kill_jobs_cb(), can you investigate?
Thanks, Christian.
[11176.741052] ============================================ [11176.741056] WARNING: possible recursive locking detected [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted [11176.741066] -------------------------------------------- [11176.741070] swapper/12/0 is trying to acquire lock: [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741088] but task is already holding lock: [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741100] other info that might help us debug this: [11176.741104] Possible unsafe locking scenario:
[11176.741108] CPU0 [11176.741110] ---- [11176.741113] lock(&fence->lock); [11176.741118] lock(&fence->lock); [11176.741122] *** DEADLOCK ***
[11176.741125] May be due to missing lock nesting notation
[11176.741128] 2 locks held by swapper/12/0: [11176.741133] #0: ffff9c339c30f768 (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741151] stack backtrace: [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 5.15.0-rc1-00031-g9d546d600800 #171 [11176.741160] Hardware name: System manufacturer System Product Name/PRIME X399-A, BIOS 0808 10/12/2018 [11176.741165] Call Trace: [11176.741169] <IRQ> [11176.741173] dump_stack_lvl+0x5b/0x74 [11176.741181] dump_stack+0x10/0x12 [11176.741186] __lock_acquire.cold+0x208/0x2df [11176.741197] lock_acquire+0xc6/0x2d0 [11176.741204] ? dma_fence_signal+0x28/0x80 [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 [11176.741219] ? dma_fence_signal+0x28/0x80 [11176.741225] dma_fence_signal+0x28/0x80 [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741254] dma_fence_signal+0x3b/0x80 [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741290] dma_fence_signal+0x3b/0x80 [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 [11176.742402] handle_irq_event_percpu+0x33/0x80 [11176.742408] handle_irq_event+0x39/0x60 [11176.742414] handle_edge_irq+0x93/0x1d0 [11176.742419] __common_interrupt+0x50/0xe0 [11176.742426] common_interrupt+0x80/0x90 [11176.742431] </IRQ> [11176.742436] asm_common_interrupt+0x1e/0x40 [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b 75 c8 48 8d 14 40 48 8d [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: 0000000000000000 [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9efeed78 [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: 0000000000000001 [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9c3350b0e800 [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: 0000000000000002 [11176.742483] ? cpuidle_enter_state+0xf8/0x470 [11176.742489] ? cpuidle_enter_state+0xf8/0x470 [11176.742495] cpuidle_enter+0x2e/0x40 [11176.742500] call_cpuidle+0x23/0x40 [11176.742506] do_idle+0x201/0x280 [11176.742512] cpu_startup_entry+0x20/0x30 [11176.742517] start_secondary+0x11f/0x160 [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb
On Fri, Oct 01, 2021 at 12:50:35PM +0200, Christian König wrote:
Hey, Andrey.
while investigating some memory management problems I've got the logdep splat below.
Looks like something is wrong with drm_sched_entity_kill_jobs_cb(), can you investigate?
Probably needs more irq_work so that we get rid of fence completion signalling recursions. -Daniel
Thanks, Christian.
[11176.741052] ============================================ [11176.741056] WARNING: possible recursive locking detected [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted [11176.741066] -------------------------------------------- [11176.741070] swapper/12/0 is trying to acquire lock: [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741088] but task is already holding lock: [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741100] other info that might help us debug this: [11176.741104] Possible unsafe locking scenario:
[11176.741108] CPU0 [11176.741110] ---- [11176.741113] lock(&fence->lock); [11176.741118] lock(&fence->lock); [11176.741122] *** DEADLOCK ***
[11176.741125] May be due to missing lock nesting notation
[11176.741128] 2 locks held by swapper/12/0: [11176.741133] #0: ffff9c339c30f768 (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741151] stack backtrace: [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 5.15.0-rc1-00031-g9d546d600800 #171 [11176.741160] Hardware name: System manufacturer System Product Name/PRIME X399-A, BIOS 0808 10/12/2018 [11176.741165] Call Trace: [11176.741169] <IRQ> [11176.741173] dump_stack_lvl+0x5b/0x74 [11176.741181] dump_stack+0x10/0x12 [11176.741186] __lock_acquire.cold+0x208/0x2df [11176.741197] lock_acquire+0xc6/0x2d0 [11176.741204] ? dma_fence_signal+0x28/0x80 [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 [11176.741219] ? dma_fence_signal+0x28/0x80 [11176.741225] dma_fence_signal+0x28/0x80 [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741254] dma_fence_signal+0x3b/0x80 [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741290] dma_fence_signal+0x3b/0x80 [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 [11176.742402] handle_irq_event_percpu+0x33/0x80 [11176.742408] handle_irq_event+0x39/0x60 [11176.742414] handle_edge_irq+0x93/0x1d0 [11176.742419] __common_interrupt+0x50/0xe0 [11176.742426] common_interrupt+0x80/0x90 [11176.742431] </IRQ> [11176.742436] asm_common_interrupt+0x1e/0x40 [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b 75 c8 48 8d 14 40 48 8d [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: 0000000000000000 [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9efeed78 [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: 0000000000000001 [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9c3350b0e800 [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: 0000000000000002 [11176.742483] ? cpuidle_enter_state+0xf8/0x470 [11176.742489] ? cpuidle_enter_state+0xf8/0x470 [11176.742495] cpuidle_enter+0x2e/0x40 [11176.742500] call_cpuidle+0x23/0x40 [11176.742506] do_idle+0x201/0x280 [11176.742512] cpu_startup_entry+0x20/0x30 [11176.742517] start_secondary+0x11f/0x160 [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb
From what I see here you supposed to have actual deadlock and not only warning, sched_fence->finished is first signaled from within hw fence done callback (drm_sched_job_done_cb) but then again from within it's own callback (drm_sched_entity_kill_jobs_cb) and so looks like same fence object is recursively signaled twice. This leads to attempt to lock fence->lock second time while it's already locked. I don't see a need to call drm_sched_fence_finished from within drm_sched_entity_kill_jobs_cb as this callback already registered on sched_fence->finished fence (entity->last_scheduled == s_fence->finished) and hence the signaling already took place.
Andrey
On 2021-10-01 6:50 a.m., Christian König wrote:
Hey, Andrey.
while investigating some memory management problems I've got the logdep splat below.
Looks like something is wrong with drm_sched_entity_kill_jobs_cb(), can you investigate?
Thanks, Christian.
[11176.741052] ============================================ [11176.741056] WARNING: possible recursive locking detected [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted [11176.741066] -------------------------------------------- [11176.741070] swapper/12/0 is trying to acquire lock: [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741088] but task is already holding lock: [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741100] other info that might help us debug this: [11176.741104] Possible unsafe locking scenario:
[11176.741108] CPU0 [11176.741110] ---- [11176.741113] lock(&fence->lock); [11176.741118] lock(&fence->lock); [11176.741122] *** DEADLOCK ***
[11176.741125] May be due to missing lock nesting notation
[11176.741128] 2 locks held by swapper/12/0: [11176.741133] #0: ffff9c339c30f768 (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741151] stack backtrace: [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 5.15.0-rc1-00031-g9d546d600800 #171 [11176.741160] Hardware name: System manufacturer System Product Name/PRIME X399-A, BIOS 0808 10/12/2018 [11176.741165] Call Trace: [11176.741169] <IRQ> [11176.741173] dump_stack_lvl+0x5b/0x74 [11176.741181] dump_stack+0x10/0x12 [11176.741186] __lock_acquire.cold+0x208/0x2df [11176.741197] lock_acquire+0xc6/0x2d0 [11176.741204] ? dma_fence_signal+0x28/0x80 [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 [11176.741219] ? dma_fence_signal+0x28/0x80 [11176.741225] dma_fence_signal+0x28/0x80 [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741254] dma_fence_signal+0x3b/0x80 [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741290] dma_fence_signal+0x3b/0x80 [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 [11176.742402] handle_irq_event_percpu+0x33/0x80 [11176.742408] handle_irq_event+0x39/0x60 [11176.742414] handle_edge_irq+0x93/0x1d0 [11176.742419] __common_interrupt+0x50/0xe0 [11176.742426] common_interrupt+0x80/0x90 [11176.742431] </IRQ> [11176.742436] asm_common_interrupt+0x1e/0x40 [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b 75 c8 48 8d 14 40 48 8d [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: 0000000000000000 [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9efeed78 [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: 0000000000000001 [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9c3350b0e800 [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: 0000000000000002 [11176.742483] ? cpuidle_enter_state+0xf8/0x470 [11176.742489] ? cpuidle_enter_state+0xf8/0x470 [11176.742495] cpuidle_enter+0x2e/0x40 [11176.742500] call_cpuidle+0x23/0x40 [11176.742506] do_idle+0x201/0x280 [11176.742512] cpu_startup_entry+0x20/0x30 [11176.742517] start_secondary+0x11f/0x160 [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb
The problem is a bit different.
The callback is on the dependent fence, while we need to signal the scheduler fence.
Daniel is right that this needs an irq_work struct to handle this properly.
Christian.
Am 01.10.21 um 17:10 schrieb Andrey Grodzovsky:
From what I see here you supposed to have actual deadlock and not only warning, sched_fence->finished is first signaled from within hw fence done callback (drm_sched_job_done_cb) but then again from within it's own callback (drm_sched_entity_kill_jobs_cb) and so looks like same fence object is recursively signaled twice. This leads to attempt to lock fence->lock second time while it's already locked. I don't see a need to call drm_sched_fence_finished from within drm_sched_entity_kill_jobs_cb as this callback already registered on sched_fence->finished fence (entity->last_scheduled == s_fence->finished) and hence the signaling already took place.
Andrey
On 2021-10-01 6:50 a.m., Christian König wrote:
Hey, Andrey.
while investigating some memory management problems I've got the logdep splat below.
Looks like something is wrong with drm_sched_entity_kill_jobs_cb(), can you investigate?
Thanks, Christian.
[11176.741052] ============================================ [11176.741056] WARNING: possible recursive locking detected [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted [11176.741066] -------------------------------------------- [11176.741070] swapper/12/0 is trying to acquire lock: [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741088] but task is already holding lock: [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741100] other info that might help us debug this: [11176.741104] Possible unsafe locking scenario:
[11176.741108] CPU0 [11176.741110] ---- [11176.741113] lock(&fence->lock); [11176.741118] lock(&fence->lock); [11176.741122] *** DEADLOCK ***
[11176.741125] May be due to missing lock nesting notation
[11176.741128] 2 locks held by swapper/12/0: [11176.741133] #0: ffff9c339c30f768 (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741151] stack backtrace: [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 5.15.0-rc1-00031-g9d546d600800 #171 [11176.741160] Hardware name: System manufacturer System Product Name/PRIME X399-A, BIOS 0808 10/12/2018 [11176.741165] Call Trace: [11176.741169] <IRQ> [11176.741173] dump_stack_lvl+0x5b/0x74 [11176.741181] dump_stack+0x10/0x12 [11176.741186] __lock_acquire.cold+0x208/0x2df [11176.741197] lock_acquire+0xc6/0x2d0 [11176.741204] ? dma_fence_signal+0x28/0x80 [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 [11176.741219] ? dma_fence_signal+0x28/0x80 [11176.741225] dma_fence_signal+0x28/0x80 [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741254] dma_fence_signal+0x3b/0x80 [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741290] dma_fence_signal+0x3b/0x80 [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 [11176.742402] handle_irq_event_percpu+0x33/0x80 [11176.742408] handle_irq_event+0x39/0x60 [11176.742414] handle_edge_irq+0x93/0x1d0 [11176.742419] __common_interrupt+0x50/0xe0 [11176.742426] common_interrupt+0x80/0x90 [11176.742431] </IRQ> [11176.742436] asm_common_interrupt+0x1e/0x40 [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b 75 c8 48 8d 14 40 48 8d [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: 0000000000000000 [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9efeed78 [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: 0000000000000001 [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9c3350b0e800 [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: 0000000000000002 [11176.742483] ? cpuidle_enter_state+0xf8/0x470 [11176.742489] ? cpuidle_enter_state+0xf8/0x470 [11176.742495] cpuidle_enter+0x2e/0x40 [11176.742500] call_cpuidle+0x23/0x40 [11176.742506] do_idle+0x201/0x280 [11176.742512] cpu_startup_entry+0x20/0x30 [11176.742517] start_secondary+0x11f/0x160 [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb
I see my confusion, we hang all unsubmitted jobs on the last submitted to HW job. Yea, in this case indeed rescheduling to a different thread context will avoid the splat but the schedule work cannot be done for each dependency signalling but rather they way we do for ttm_bo_delayed_delete with a list of dependencies to signal. Otherwise some of the schedule work will be drop because previous invocation is still pending execution.
Andrey
On 2021-10-04 4:14 a.m., Christian König wrote:
The problem is a bit different.
The callback is on the dependent fence, while we need to signal the scheduler fence.
Daniel is right that this needs an irq_work struct to handle this properly.
Christian.
Am 01.10.21 um 17:10 schrieb Andrey Grodzovsky:
From what I see here you supposed to have actual deadlock and not only warning, sched_fence->finished is first signaled from within hw fence done callback (drm_sched_job_done_cb) but then again from within it's own callback (drm_sched_entity_kill_jobs_cb) and so looks like same fence object is recursively signaled twice. This leads to attempt to lock fence->lock second time while it's already locked. I don't see a need to call drm_sched_fence_finished from within drm_sched_entity_kill_jobs_cb as this callback already registered on sched_fence->finished fence (entity->last_scheduled == s_fence->finished) and hence the signaling already took place.
Andrey
On 2021-10-01 6:50 a.m., Christian König wrote:
Hey, Andrey.
while investigating some memory management problems I've got the logdep splat below.
Looks like something is wrong with drm_sched_entity_kill_jobs_cb(), can you investigate?
Thanks, Christian.
[11176.741052] ============================================ [11176.741056] WARNING: possible recursive locking detected [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted [11176.741066] -------------------------------------------- [11176.741070] swapper/12/0 is trying to acquire lock: [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741088] but task is already holding lock: [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741100] other info that might help us debug this: [11176.741104] Possible unsafe locking scenario:
[11176.741108] CPU0 [11176.741110] ---- [11176.741113] lock(&fence->lock); [11176.741118] lock(&fence->lock); [11176.741122] *** DEADLOCK ***
[11176.741125] May be due to missing lock nesting notation
[11176.741128] 2 locks held by swapper/12/0: [11176.741133] #0: ffff9c339c30f768 (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741151] stack backtrace: [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 5.15.0-rc1-00031-g9d546d600800 #171 [11176.741160] Hardware name: System manufacturer System Product Name/PRIME X399-A, BIOS 0808 10/12/2018 [11176.741165] Call Trace: [11176.741169] <IRQ> [11176.741173] dump_stack_lvl+0x5b/0x74 [11176.741181] dump_stack+0x10/0x12 [11176.741186] __lock_acquire.cold+0x208/0x2df [11176.741197] lock_acquire+0xc6/0x2d0 [11176.741204] ? dma_fence_signal+0x28/0x80 [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 [11176.741219] ? dma_fence_signal+0x28/0x80 [11176.741225] dma_fence_signal+0x28/0x80 [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741254] dma_fence_signal+0x3b/0x80 [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741290] dma_fence_signal+0x3b/0x80 [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 [11176.742402] handle_irq_event_percpu+0x33/0x80 [11176.742408] handle_irq_event+0x39/0x60 [11176.742414] handle_edge_irq+0x93/0x1d0 [11176.742419] __common_interrupt+0x50/0xe0 [11176.742426] common_interrupt+0x80/0x90 [11176.742431] </IRQ> [11176.742436] asm_common_interrupt+0x1e/0x40 [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b 75 c8 48 8d 14 40 48 8d [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: 0000000000000000 [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9efeed78 [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: 0000000000000001 [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9c3350b0e800 [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: 0000000000000002 [11176.742483] ? cpuidle_enter_state+0xf8/0x470 [11176.742489] ? cpuidle_enter_state+0xf8/0x470 [11176.742495] cpuidle_enter+0x2e/0x40 [11176.742500] call_cpuidle+0x23/0x40 [11176.742506] do_idle+0x201/0x280 [11176.742512] cpu_startup_entry+0x20/0x30 [11176.742517] start_secondary+0x11f/0x160 [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb
On 2021-10-04 4:14 a.m., Christian König wrote:
The problem is a bit different.
The callback is on the dependent fence, while we need to signal the scheduler fence.
Daniel is right that this needs an irq_work struct to handle this properly.
Christian.
So we had some discussions with Christian regarding irq_work and agreed I should look into doing it but stepping back for a sec -
Why we insist on calling the dma_fence_cb with fence->lock locked ? Is it because of dma_fence_add_callback ? Because we first test for DMA_FENCE_FLAG_SIGNALED_BIT and only after that lock the fence->lock ? If so, can't we move DMA_FENCE_FLAG_SIGNALED_BIT check inside the locked section ? Because if in theory we could call the cb with unlocked fence->lock (i.e. this kind of iteration https://elixir.bootlin.com/linux/v5.15-rc6/source/drivers/gpu/drm/ttm/ttm_re...) we wouldn't have the lockdep splat. And in general, is it really the correct approach to call a third party code from a call back with locked spinlock ? We don't know what the cb does inside and I don't see any explicit restrictions in documentation of dma_fence_func_t what can and cannot be done there.
Andrey
Am 01.10.21 um 17:10 schrieb Andrey Grodzovsky:
From what I see here you supposed to have actual deadlock and not only warning, sched_fence->finished is first signaled from within hw fence done callback (drm_sched_job_done_cb) but then again from within it's own callback (drm_sched_entity_kill_jobs_cb) and so looks like same fence object is recursively signaled twice. This leads to attempt to lock fence->lock second time while it's already locked. I don't see a need to call drm_sched_fence_finished from within drm_sched_entity_kill_jobs_cb as this callback already registered on sched_fence->finished fence (entity->last_scheduled == s_fence->finished) and hence the signaling already took place.
Andrey
On 2021-10-01 6:50 a.m., Christian König wrote:
Hey, Andrey.
while investigating some memory management problems I've got the logdep splat below.
Looks like something is wrong with drm_sched_entity_kill_jobs_cb(), can you investigate?
Thanks, Christian.
[11176.741052] ============================================ [11176.741056] WARNING: possible recursive locking detected [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted [11176.741066] -------------------------------------------- [11176.741070] swapper/12/0 is trying to acquire lock: [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741088] but task is already holding lock: [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741100] other info that might help us debug this: [11176.741104] Possible unsafe locking scenario:
[11176.741108] CPU0 [11176.741110] ---- [11176.741113] lock(&fence->lock); [11176.741118] lock(&fence->lock); [11176.741122] *** DEADLOCK ***
[11176.741125] May be due to missing lock nesting notation
[11176.741128] 2 locks held by swapper/12/0: [11176.741133] #0: ffff9c339c30f768 (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741151] stack backtrace: [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 5.15.0-rc1-00031-g9d546d600800 #171 [11176.741160] Hardware name: System manufacturer System Product Name/PRIME X399-A, BIOS 0808 10/12/2018 [11176.741165] Call Trace: [11176.741169] <IRQ> [11176.741173] dump_stack_lvl+0x5b/0x74 [11176.741181] dump_stack+0x10/0x12 [11176.741186] __lock_acquire.cold+0x208/0x2df [11176.741197] lock_acquire+0xc6/0x2d0 [11176.741204] ? dma_fence_signal+0x28/0x80 [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 [11176.741219] ? dma_fence_signal+0x28/0x80 [11176.741225] dma_fence_signal+0x28/0x80 [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741254] dma_fence_signal+0x3b/0x80 [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741290] dma_fence_signal+0x3b/0x80 [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 [11176.742402] handle_irq_event_percpu+0x33/0x80 [11176.742408] handle_irq_event+0x39/0x60 [11176.742414] handle_edge_irq+0x93/0x1d0 [11176.742419] __common_interrupt+0x50/0xe0 [11176.742426] common_interrupt+0x80/0x90 [11176.742431] </IRQ> [11176.742436] asm_common_interrupt+0x1e/0x40 [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b 75 c8 48 8d 14 40 48 8d [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: 0000000000000000 [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9efeed78 [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: 0000000000000001 [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9c3350b0e800 [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: 0000000000000002 [11176.742483] ? cpuidle_enter_state+0xf8/0x470 [11176.742489] ? cpuidle_enter_state+0xf8/0x470 [11176.742495] cpuidle_enter+0x2e/0x40 [11176.742500] call_cpuidle+0x23/0x40 [11176.742506] do_idle+0x201/0x280 [11176.742512] cpu_startup_entry+0x20/0x30 [11176.742517] start_secondary+0x11f/0x160 [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb
Am 20.10.21 um 21:32 schrieb Andrey Grodzovsky:
On 2021-10-04 4:14 a.m., Christian König wrote:
The problem is a bit different.
The callback is on the dependent fence, while we need to signal the scheduler fence.
Daniel is right that this needs an irq_work struct to handle this properly.
Christian.
So we had some discussions with Christian regarding irq_work and agreed I should look into doing it but stepping back for a sec -
Why we insist on calling the dma_fence_cb with fence->lock locked ? Is it because of dma_fence_add_callback ? Because we first test for DMA_FENCE_FLAG_SIGNALED_BIT and only after that lock the fence->lock ? If so, can't we move DMA_FENCE_FLAG_SIGNALED_BIT check inside the locked section ? Because if in theory we could call the cb with unlocked fence->lock (i.e. this kind of iteration https://elixir.bootlin.com/linux/v5.15-rc6/source/drivers/gpu/drm/ttm/ttm_re...) we wouldn't have the lockdep splat. And in general, is it really the correct approach to call a third party code from a call back with locked spinlock ? We don't know what the cb does inside and I don't see any explicit restrictions in documentation of dma_fence_func_t what can and cannot be done there.
Yeah, that's exactly what I meant with using the irq_work directly in the fence code.
The problem is dma_fence_signal_locked() which is used by quite a number of drivers to signal the fence while holding the lock.
Otherwise we could indeed simplify the fence handling a lot.
Christian.
Andrey
Am 01.10.21 um 17:10 schrieb Andrey Grodzovsky:
From what I see here you supposed to have actual deadlock and not only warning, sched_fence->finished is first signaled from within hw fence done callback (drm_sched_job_done_cb) but then again from within it's own callback (drm_sched_entity_kill_jobs_cb) and so looks like same fence object is recursively signaled twice. This leads to attempt to lock fence->lock second time while it's already locked. I don't see a need to call drm_sched_fence_finished from within drm_sched_entity_kill_jobs_cb as this callback already registered on sched_fence->finished fence (entity->last_scheduled == s_fence->finished) and hence the signaling already took place.
Andrey
On 2021-10-01 6:50 a.m., Christian König wrote:
Hey, Andrey.
while investigating some memory management problems I've got the logdep splat below.
Looks like something is wrong with drm_sched_entity_kill_jobs_cb(), can you investigate?
Thanks, Christian.
[11176.741052] ============================================ [11176.741056] WARNING: possible recursive locking detected [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted [11176.741066] -------------------------------------------- [11176.741070] swapper/12/0 is trying to acquire lock: [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741088] but task is already holding lock: [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741100] other info that might help us debug this: [11176.741104] Possible unsafe locking scenario:
[11176.741108] CPU0 [11176.741110] ---- [11176.741113] lock(&fence->lock); [11176.741118] lock(&fence->lock); [11176.741122] *** DEADLOCK ***
[11176.741125] May be due to missing lock nesting notation
[11176.741128] 2 locks held by swapper/12/0: [11176.741133] #0: ffff9c339c30f768 (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741151] stack backtrace: [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 5.15.0-rc1-00031-g9d546d600800 #171 [11176.741160] Hardware name: System manufacturer System Product Name/PRIME X399-A, BIOS 0808 10/12/2018 [11176.741165] Call Trace: [11176.741169] <IRQ> [11176.741173] dump_stack_lvl+0x5b/0x74 [11176.741181] dump_stack+0x10/0x12 [11176.741186] __lock_acquire.cold+0x208/0x2df [11176.741197] lock_acquire+0xc6/0x2d0 [11176.741204] ? dma_fence_signal+0x28/0x80 [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 [11176.741219] ? dma_fence_signal+0x28/0x80 [11176.741225] dma_fence_signal+0x28/0x80 [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741254] dma_fence_signal+0x3b/0x80 [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741290] dma_fence_signal+0x3b/0x80 [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 [11176.742402] handle_irq_event_percpu+0x33/0x80 [11176.742408] handle_irq_event+0x39/0x60 [11176.742414] handle_edge_irq+0x93/0x1d0 [11176.742419] __common_interrupt+0x50/0xe0 [11176.742426] common_interrupt+0x80/0x90 [11176.742431] </IRQ> [11176.742436] asm_common_interrupt+0x1e/0x40 [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b 75 c8 48 8d 14 40 48 8d [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: 0000000000000000 [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9efeed78 [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: 0000000000000001 [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9c3350b0e800 [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: 0000000000000002 [11176.742483] ? cpuidle_enter_state+0xf8/0x470 [11176.742489] ? cpuidle_enter_state+0xf8/0x470 [11176.742495] cpuidle_enter+0x2e/0x40 [11176.742500] call_cpuidle+0x23/0x40 [11176.742506] do_idle+0x201/0x280 [11176.742512] cpu_startup_entry+0x20/0x30 [11176.742517] start_secondary+0x11f/0x160 [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb
Adding back Daniel (somehow he got off the addresses list) and Chris who worked a lot in this area.
On 2021-10-21 2:34 a.m., Christian König wrote:
Am 20.10.21 um 21:32 schrieb Andrey Grodzovsky:
On 2021-10-04 4:14 a.m., Christian König wrote:
The problem is a bit different.
The callback is on the dependent fence, while we need to signal the scheduler fence.
Daniel is right that this needs an irq_work struct to handle this properly.
Christian.
So we had some discussions with Christian regarding irq_work and agreed I should look into doing it but stepping back for a sec -
Why we insist on calling the dma_fence_cb with fence->lock locked ? Is it because of dma_fence_add_callback ? Because we first test for DMA_FENCE_FLAG_SIGNALED_BIT and only after that lock the fence->lock ? If so, can't we move DMA_FENCE_FLAG_SIGNALED_BIT check inside the locked section ? Because if in theory we could call the cb with unlocked fence->lock (i.e. this kind of iteration https://elixir.bootlin.com/linux/v5.15-rc6/source/drivers/gpu/drm/ttm/ttm_re...) we wouldn't have the lockdep splat. And in general, is it really the correct approach to call a third party code from a call back with locked spinlock ? We don't know what the cb does inside and I don't see any explicit restrictions in documentation of dma_fence_func_t what can and cannot be done there.
Yeah, that's exactly what I meant with using the irq_work directly in the fence code.
My idea is not to use irq work at all but instead to implement unlocked dma_fence cb execution using iteration which drops the spinlock each time next cb is executed and acquiring it again after (until cb_list is empy).
The problem is dma_fence_signal_locked() which is used by quite a number of drivers to signal the fence while holding the lock.
For this I think we should not reuse dma_fence_signal_locked inside dma_fence_signal and instead implement it using the unlocked iteration I mentioned above. I looked a bit in the code and the history and I see that until some time ago (this commit by Chris 0fc89b6802ba1fcc561b0c906e0cefd384e3b2e5), indeed dma_fence_signal was doing it's own, locked iteration and wasn't reusing dma_fence_signal_locked. This way whoever relies on the dma_fence_signal_locked won't be impacted an who is not (like us in drm_sched_fence_scheduled/drm_sched_fence_finished) should also not be impacted by more narrow scope of the lock. I also looked at dma_fence_default_wait and how it locks the fence->lock and check if fence is signaled before wait start and I don't see a problem there either.
I attached quick draft of this proposal to clarify.
Andrey
Otherwise we could indeed simplify the fence handling a lot.
Christian.
Andrey
Am 01.10.21 um 17:10 schrieb Andrey Grodzovsky:
From what I see here you supposed to have actual deadlock and not only warning, sched_fence->finished is first signaled from within hw fence done callback (drm_sched_job_done_cb) but then again from within it's own callback (drm_sched_entity_kill_jobs_cb) and so looks like same fence object is recursively signaled twice. This leads to attempt to lock fence->lock second time while it's already locked. I don't see a need to call drm_sched_fence_finished from within drm_sched_entity_kill_jobs_cb as this callback already registered on sched_fence->finished fence (entity->last_scheduled == s_fence->finished) and hence the signaling already took place.
Andrey
On 2021-10-01 6:50 a.m., Christian König wrote:
Hey, Andrey.
while investigating some memory management problems I've got the logdep splat below.
Looks like something is wrong with drm_sched_entity_kill_jobs_cb(), can you investigate?
Thanks, Christian.
[11176.741052] ============================================ [11176.741056] WARNING: possible recursive locking detected [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted [11176.741066] -------------------------------------------- [11176.741070] swapper/12/0 is trying to acquire lock: [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741088] but task is already holding lock: [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741100] other info that might help us debug this: [11176.741104] Possible unsafe locking scenario:
[11176.741108] CPU0 [11176.741110] ---- [11176.741113] lock(&fence->lock); [11176.741118] lock(&fence->lock); [11176.741122] *** DEADLOCK ***
[11176.741125] May be due to missing lock nesting notation
[11176.741128] 2 locks held by swapper/12/0: [11176.741133] #0: ffff9c339c30f768 (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741151] stack backtrace: [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 5.15.0-rc1-00031-g9d546d600800 #171 [11176.741160] Hardware name: System manufacturer System Product Name/PRIME X399-A, BIOS 0808 10/12/2018 [11176.741165] Call Trace: [11176.741169] <IRQ> [11176.741173] dump_stack_lvl+0x5b/0x74 [11176.741181] dump_stack+0x10/0x12 [11176.741186] __lock_acquire.cold+0x208/0x2df [11176.741197] lock_acquire+0xc6/0x2d0 [11176.741204] ? dma_fence_signal+0x28/0x80 [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 [11176.741219] ? dma_fence_signal+0x28/0x80 [11176.741225] dma_fence_signal+0x28/0x80 [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741254] dma_fence_signal+0x3b/0x80 [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741290] dma_fence_signal+0x3b/0x80 [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 [11176.742402] handle_irq_event_percpu+0x33/0x80 [11176.742408] handle_irq_event+0x39/0x60 [11176.742414] handle_edge_irq+0x93/0x1d0 [11176.742419] __common_interrupt+0x50/0xe0 [11176.742426] common_interrupt+0x80/0x90 [11176.742431] </IRQ> [11176.742436] asm_common_interrupt+0x1e/0x40 [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b 75 c8 48 8d 14 40 48 8d [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: 0000000000000000 [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9efeed78 [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: 0000000000000001 [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9c3350b0e800 [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: 0000000000000002 [11176.742483] ? cpuidle_enter_state+0xf8/0x470 [11176.742489] ? cpuidle_enter_state+0xf8/0x470 [11176.742495] cpuidle_enter+0x2e/0x40 [11176.742500] call_cpuidle+0x23/0x40 [11176.742506] do_idle+0x201/0x280 [11176.742512] cpu_startup_entry+0x20/0x30 [11176.742517] start_secondary+0x11f/0x160 [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb
In general I'm all there to get this fixed, but there is one major problem: Drivers don't expect the lock to be dropped.
What we could do is to change all drivers so they call always call the dma_fence_signal functions and drop the _locked variants. This way we could move calling the callback out of the spinlock.
But that requires audit of all drivers, so quite a lot of work to do.
Regards, Christian.
Am 25.10.21 um 21:10 schrieb Andrey Grodzovsky:
Adding back Daniel (somehow he got off the addresses list) and Chris who worked a lot in this area.
On 2021-10-21 2:34 a.m., Christian König wrote:
Am 20.10.21 um 21:32 schrieb Andrey Grodzovsky:
On 2021-10-04 4:14 a.m., Christian König wrote:
The problem is a bit different.
The callback is on the dependent fence, while we need to signal the scheduler fence.
Daniel is right that this needs an irq_work struct to handle this properly.
Christian.
So we had some discussions with Christian regarding irq_work and agreed I should look into doing it but stepping back for a sec -
Why we insist on calling the dma_fence_cb with fence->lock locked ? Is it because of dma_fence_add_callback ? Because we first test for DMA_FENCE_FLAG_SIGNALED_BIT and only after that lock the fence->lock ? If so, can't we move DMA_FENCE_FLAG_SIGNALED_BIT check inside the locked section ? Because if in theory we could call the cb with unlocked fence->lock (i.e. this kind of iteration https://elixir.bootlin.com/linux/v5.15-rc6/source/drivers/gpu/drm/ttm/ttm_re...) we wouldn't have the lockdep splat. And in general, is it really the correct approach to call a third party code from a call back with locked spinlock ? We don't know what the cb does inside and I don't see any explicit restrictions in documentation of dma_fence_func_t what can and cannot be done there.
Yeah, that's exactly what I meant with using the irq_work directly in the fence code.
My idea is not to use irq work at all but instead to implement unlocked dma_fence cb execution using iteration which drops the spinlock each time next cb is executed and acquiring it again after (until cb_list is empy).
The problem is dma_fence_signal_locked() which is used by quite a number of drivers to signal the fence while holding the lock.
For this I think we should not reuse dma_fence_signal_locked inside dma_fence_signal and instead implement it using the unlocked iteration I mentioned above. I looked a bit in the code and the history and I see that until some time ago (this commit by Chris 0fc89b6802ba1fcc561b0c906e0cefd384e3b2e5), indeed dma_fence_signal was doing it's own, locked iteration and wasn't reusing dma_fence_signal_locked. This way whoever relies on the dma_fence_signal_locked won't be impacted an who is not (like us in drm_sched_fence_scheduled/drm_sched_fence_finished) should also not be impacted by more narrow scope of the lock. I also looked at dma_fence_default_wait and how it locks the fence->lock and check if fence is signaled before wait start and I don't see a problem there either.
I attached quick draft of this proposal to clarify.
Andrey
Otherwise we could indeed simplify the fence handling a lot.
Christian.
Andrey
Am 01.10.21 um 17:10 schrieb Andrey Grodzovsky:
From what I see here you supposed to have actual deadlock and not only warning, sched_fence->finished is first signaled from within hw fence done callback (drm_sched_job_done_cb) but then again from within it's own callback (drm_sched_entity_kill_jobs_cb) and so looks like same fence object is recursively signaled twice. This leads to attempt to lock fence->lock second time while it's already locked. I don't see a need to call drm_sched_fence_finished from within drm_sched_entity_kill_jobs_cb as this callback already registered on sched_fence->finished fence (entity->last_scheduled == s_fence->finished) and hence the signaling already took place.
Andrey
On 2021-10-01 6:50 a.m., Christian König wrote:
Hey, Andrey.
while investigating some memory management problems I've got the logdep splat below.
Looks like something is wrong with drm_sched_entity_kill_jobs_cb(), can you investigate?
Thanks, Christian.
[11176.741052] ============================================ [11176.741056] WARNING: possible recursive locking detected [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted [11176.741066] -------------------------------------------- [11176.741070] swapper/12/0 is trying to acquire lock: [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741088] but task is already holding lock: [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741100] other info that might help us debug this: [11176.741104] Possible unsafe locking scenario:
[11176.741108] CPU0 [11176.741110] ---- [11176.741113] lock(&fence->lock); [11176.741118] lock(&fence->lock); [11176.741122] *** DEADLOCK ***
[11176.741125] May be due to missing lock nesting notation
[11176.741128] 2 locks held by swapper/12/0: [11176.741133] #0: ffff9c339c30f768 (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 [11176.741151] stack backtrace: [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 5.15.0-rc1-00031-g9d546d600800 #171 [11176.741160] Hardware name: System manufacturer System Product Name/PRIME X399-A, BIOS 0808 10/12/2018 [11176.741165] Call Trace: [11176.741169] <IRQ> [11176.741173] dump_stack_lvl+0x5b/0x74 [11176.741181] dump_stack+0x10/0x12 [11176.741186] __lock_acquire.cold+0x208/0x2df [11176.741197] lock_acquire+0xc6/0x2d0 [11176.741204] ? dma_fence_signal+0x28/0x80 [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 [11176.741219] ? dma_fence_signal+0x28/0x80 [11176.741225] dma_fence_signal+0x28/0x80 [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741254] dma_fence_signal+0x3b/0x80 [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 [11176.741290] dma_fence_signal+0x3b/0x80 [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 [11176.742402] handle_irq_event_percpu+0x33/0x80 [11176.742408] handle_irq_event+0x39/0x60 [11176.742414] handle_edge_irq+0x93/0x1d0 [11176.742419] __common_interrupt+0x50/0xe0 [11176.742426] common_interrupt+0x80/0x90 [11176.742431] </IRQ> [11176.742436] asm_common_interrupt+0x1e/0x40 [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b 75 c8 48 8d 14 40 48 8d [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: 0000000000000000 [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9efeed78 [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: 0000000000000001 [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9c3350b0e800 [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: 0000000000000002 [11176.742483] ? cpuidle_enter_state+0xf8/0x470 [11176.742489] ? cpuidle_enter_state+0xf8/0x470 [11176.742495] cpuidle_enter+0x2e/0x40 [11176.742500] call_cpuidle+0x23/0x40 [11176.742506] do_idle+0x201/0x280 [11176.742512] cpu_startup_entry+0x20/0x30 [11176.742517] start_secondary+0x11f/0x160 [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb
On 2021-10-25 3:56 p.m., Christian König wrote:
In general I'm all there to get this fixed, but there is one major problem: Drivers don't expect the lock to be dropped.
I am probably missing something but in my approach we only modify the code for those clients that call dma_fence_signal, not dma_fence_signal_locked. In those cases the drivers are agnostic to lock behavior (or should be at least) since the lock is acquired within the dma fence code. Note that if you are worried about calling the callback without lock then same exact concern is relevant to using the irq_work directly in the fence code since the irq_work will execute at a later time without locked fence->lock (which is the point of using irq_work).
What we could do is to change all drivers so they call always call the dma_fence_signal functions and drop the _locked variants. This way we could move calling the callback out of the spinlock.
But that requires audit of all drivers, so quite a lot of work to do.
As i said earlier - if we only modify dma_fence_signal and don't touch dma_fence_signal_locked then our only concern should the users of dma_fence_signal. Let me please know if I am still missing some point of yours.
Andrey
Regards, Christian.
Am 25.10.21 um 21:10 schrieb Andrey Grodzovsky:
Adding back Daniel (somehow he got off the addresses list) and Chris who worked a lot in this area.
On 2021-10-21 2:34 a.m., Christian König wrote:
Am 20.10.21 um 21:32 schrieb Andrey Grodzovsky:
On 2021-10-04 4:14 a.m., Christian König wrote:
The problem is a bit different.
The callback is on the dependent fence, while we need to signal the scheduler fence.
Daniel is right that this needs an irq_work struct to handle this properly.
Christian.
So we had some discussions with Christian regarding irq_work and agreed I should look into doing it but stepping back for a sec -
Why we insist on calling the dma_fence_cb with fence->lock locked ? Is it because of dma_fence_add_callback ? Because we first test for DMA_FENCE_FLAG_SIGNALED_BIT and only after that lock the fence->lock ? If so, can't we move DMA_FENCE_FLAG_SIGNALED_BIT check inside the locked section ? Because if in theory we could call the cb with unlocked fence->lock (i.e. this kind of iteration https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir.boo...) we wouldn't have the lockdep splat. And in general, is it really the correct approach to call a third party code from a call back with locked spinlock ? We don't know what the cb does inside and I don't see any explicit restrictions in documentation of dma_fence_func_t what can and cannot be done there.
Yeah, that's exactly what I meant with using the irq_work directly in the fence code.
My idea is not to use irq work at all but instead to implement unlocked dma_fence cb execution using iteration which drops the spinlock each time next cb is executed and acquiring it again after (until cb_list is empy).
The problem is dma_fence_signal_locked() which is used by quite a number of drivers to signal the fence while holding the lock.
For this I think we should not reuse dma_fence_signal_locked inside dma_fence_signal and instead implement it using the unlocked iteration I mentioned above. I looked a bit in the code and the history and I see that until some time ago (this commit by Chris 0fc89b6802ba1fcc561b0c906e0cefd384e3b2e5), indeed dma_fence_signal was doing it's own, locked iteration and wasn't reusing dma_fence_signal_locked. This way whoever relies on the dma_fence_signal_locked won't be impacted an who is not (like us in drm_sched_fence_scheduled/drm_sched_fence_finished) should also not be impacted by more narrow scope of the lock. I also looked at dma_fence_default_wait and how it locks the fence->lock and check if fence is signaled before wait start and I don't see a problem there either.
I attached quick draft of this proposal to clarify.
Andrey
Otherwise we could indeed simplify the fence handling a lot.
Christian.
Andrey
Am 01.10.21 um 17:10 schrieb Andrey Grodzovsky:
From what I see here you supposed to have actual deadlock and not only warning, sched_fence->finished is first signaled from within hw fence done callback (drm_sched_job_done_cb) but then again from within it's own callback (drm_sched_entity_kill_jobs_cb) and so looks like same fence object is recursively signaled twice. This leads to attempt to lock fence->lock second time while it's already locked. I don't see a need to call drm_sched_fence_finished from within drm_sched_entity_kill_jobs_cb as this callback already registered on sched_fence->finished fence (entity->last_scheduled == s_fence->finished) and hence the signaling already took place.
Andrey
On 2021-10-01 6:50 a.m., Christian König wrote: > Hey, Andrey. > > while investigating some memory management problems I've got the > logdep splat below. > > Looks like something is wrong with > drm_sched_entity_kill_jobs_cb(), can you investigate? > > Thanks, > Christian. > > [11176.741052] ============================================ > [11176.741056] WARNING: possible recursive locking detected > [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted > [11176.741066] -------------------------------------------- > [11176.741070] swapper/12/0 is trying to acquire lock: > [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: > dma_fence_signal+0x28/0x80 > [11176.741088] > but task is already holding lock: > [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: > dma_fence_signal+0x28/0x80 > [11176.741100] > other info that might help us debug this: > [11176.741104] Possible unsafe locking scenario: > > [11176.741108] CPU0 > [11176.741110] ---- > [11176.741113] lock(&fence->lock); > [11176.741118] lock(&fence->lock); > [11176.741122] > *** DEADLOCK *** > > [11176.741125] May be due to missing lock nesting notation > > [11176.741128] 2 locks held by swapper/12/0: > [11176.741133] #0: ffff9c339c30f768 > (&ring->fence_drv.lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 > [11176.741142] #1: ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, > at: dma_fence_signal+0x28/0x80 > [11176.741151] > stack backtrace: > [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted > 5.15.0-rc1-00031-g9d546d600800 #171 > [11176.741160] Hardware name: System manufacturer System Product > Name/PRIME X399-A, BIOS 0808 10/12/2018 > [11176.741165] Call Trace: > [11176.741169] <IRQ> > [11176.741173] dump_stack_lvl+0x5b/0x74 > [11176.741181] dump_stack+0x10/0x12 > [11176.741186] __lock_acquire.cold+0x208/0x2df > [11176.741197] lock_acquire+0xc6/0x2d0 > [11176.741204] ? dma_fence_signal+0x28/0x80 > [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 > [11176.741219] ? dma_fence_signal+0x28/0x80 > [11176.741225] dma_fence_signal+0x28/0x80 > [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] > [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] > [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 > [11176.741254] dma_fence_signal+0x3b/0x80 > [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] > [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] > [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] > [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 > [11176.741290] dma_fence_signal+0x3b/0x80 > [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] > [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] > [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] > [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] > [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] > [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 > [11176.742402] handle_irq_event_percpu+0x33/0x80 > [11176.742408] handle_irq_event+0x39/0x60 > [11176.742414] handle_edge_irq+0x93/0x1d0 > [11176.742419] __common_interrupt+0x50/0xe0 > [11176.742426] common_interrupt+0x80/0x90 > [11176.742431] </IRQ> > [11176.742436] asm_common_interrupt+0x1e/0x40 > [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 > [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 > ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff > fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c 2b > 75 c8 48 8d 14 40 48 8d > [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 > [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: > 0000000000000000 > [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: > ffffffff9efeed78 > [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: > 0000000000000001 > [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: > ffff9c3350b0e800 > [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: > 0000000000000002 > [11176.742483] ? cpuidle_enter_state+0xf8/0x470 > [11176.742489] ? cpuidle_enter_state+0xf8/0x470 > [11176.742495] cpuidle_enter+0x2e/0x40 > [11176.742500] call_cpuidle+0x23/0x40 > [11176.742506] do_idle+0x201/0x280 > [11176.742512] cpu_startup_entry+0x20/0x30 > [11176.742517] start_secondary+0x11f/0x160 > [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb >
Am 26.10.21 um 04:33 schrieb Andrey Grodzovsky:
On 2021-10-25 3:56 p.m., Christian König wrote:
In general I'm all there to get this fixed, but there is one major problem: Drivers don't expect the lock to be dropped.
I am probably missing something but in my approach we only modify the code for those clients that call dma_fence_signal, not dma_fence_signal_locked. In those cases the drivers are agnostic to lock behavior (or should be at least) since the lock is acquired within the dma fence code. Note that if you are worried about calling the callback without lock then same exact concern is relevant to using the irq_work directly in the fence code since the irq_work will execute at a later time without locked fence->lock (which is the point of using irq_work).
Yeah, I've seen that it just doesn't make much sense to me.
What we could do is to change all drivers so they call always call the dma_fence_signal functions and drop the _locked variants. This way we could move calling the callback out of the spinlock.
But that requires audit of all drivers, so quite a lot of work to do.
As i said earlier - if we only modify dma_fence_signal and don't touch dma_fence_signal_locked then our only concern should the users of dma_fence_signal.
Yes, but what do you do with the drivers who call the _locked variant?
Let me please know if I am still missing some point of yours.
Well, I mean we need to be able to handle this for all drivers.
Regards, Christian.
Andrey
Regards, Christian.
Am 25.10.21 um 21:10 schrieb Andrey Grodzovsky:
Adding back Daniel (somehow he got off the addresses list) and Chris who worked a lot in this area.
On 2021-10-21 2:34 a.m., Christian König wrote:
Am 20.10.21 um 21:32 schrieb Andrey Grodzovsky:
On 2021-10-04 4:14 a.m., Christian König wrote:
The problem is a bit different.
The callback is on the dependent fence, while we need to signal the scheduler fence.
Daniel is right that this needs an irq_work struct to handle this properly.
Christian.
So we had some discussions with Christian regarding irq_work and agreed I should look into doing it but stepping back for a sec -
Why we insist on calling the dma_fence_cb with fence->lock locked ? Is it because of dma_fence_add_callback ? Because we first test for DMA_FENCE_FLAG_SIGNALED_BIT and only after that lock the fence->lock ? If so, can't we move DMA_FENCE_FLAG_SIGNALED_BIT check inside the locked section ? Because if in theory we could call the cb with unlocked fence->lock (i.e. this kind of iteration https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir.boo...) we wouldn't have the lockdep splat. And in general, is it really the correct approach to call a third party code from a call back with locked spinlock ? We don't know what the cb does inside and I don't see any explicit restrictions in documentation of dma_fence_func_t what can and cannot be done there.
Yeah, that's exactly what I meant with using the irq_work directly in the fence code.
My idea is not to use irq work at all but instead to implement unlocked dma_fence cb execution using iteration which drops the spinlock each time next cb is executed and acquiring it again after (until cb_list is empy).
The problem is dma_fence_signal_locked() which is used by quite a number of drivers to signal the fence while holding the lock.
For this I think we should not reuse dma_fence_signal_locked inside dma_fence_signal and instead implement it using the unlocked iteration I mentioned above. I looked a bit in the code and the history and I see that until some time ago (this commit by Chris 0fc89b6802ba1fcc561b0c906e0cefd384e3b2e5), indeed dma_fence_signal was doing it's own, locked iteration and wasn't reusing dma_fence_signal_locked. This way whoever relies on the dma_fence_signal_locked won't be impacted an who is not (like us in drm_sched_fence_scheduled/drm_sched_fence_finished) should also not be impacted by more narrow scope of the lock. I also looked at dma_fence_default_wait and how it locks the fence->lock and check if fence is signaled before wait start and I don't see a problem there either.
I attached quick draft of this proposal to clarify.
Andrey
Otherwise we could indeed simplify the fence handling a lot.
Christian.
Andrey
Am 01.10.21 um 17:10 schrieb Andrey Grodzovsky: > From what I see here you supposed to have actual deadlock and > not only warning, sched_fence->finished is first signaled from > within > hw fence done callback (drm_sched_job_done_cb) but then again > from within it's own callback (drm_sched_entity_kill_jobs_cb) > and so > looks like same fence object is recursively signaled twice. > This leads to attempt to lock fence->lock second time while it's > already > locked. I don't see a need to call drm_sched_fence_finished from > within drm_sched_entity_kill_jobs_cb as this callback already > registered > on sched_fence->finished fence (entity->last_scheduled == > s_fence->finished) and hence the signaling already took place. > > Andrey > > On 2021-10-01 6:50 a.m., Christian König wrote: >> Hey, Andrey. >> >> while investigating some memory management problems I've got >> the logdep splat below. >> >> Looks like something is wrong with >> drm_sched_entity_kill_jobs_cb(), can you investigate? >> >> Thanks, >> Christian. >> >> [11176.741052] ============================================ >> [11176.741056] WARNING: possible recursive locking detected >> [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted >> [11176.741066] -------------------------------------------- >> [11176.741070] swapper/12/0 is trying to acquire lock: >> [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, at: >> dma_fence_signal+0x28/0x80 >> [11176.741088] >> but task is already holding lock: >> [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, at: >> dma_fence_signal+0x28/0x80 >> [11176.741100] >> other info that might help us debug this: >> [11176.741104] Possible unsafe locking scenario: >> >> [11176.741108] CPU0 >> [11176.741110] ---- >> [11176.741113] lock(&fence->lock); >> [11176.741118] lock(&fence->lock); >> [11176.741122] >> *** DEADLOCK *** >> >> [11176.741125] May be due to missing lock nesting notation >> >> [11176.741128] 2 locks held by swapper/12/0: >> [11176.741133] #0: ffff9c339c30f768 >> (&ring->fence_drv.lock){-.-.}-{3:3}, at: >> dma_fence_signal+0x28/0x80 >> [11176.741142] #1: ffff9c337ed172a8 >> (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 >> [11176.741151] >> stack backtrace: >> [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted >> 5.15.0-rc1-00031-g9d546d600800 #171 >> [11176.741160] Hardware name: System manufacturer System >> Product Name/PRIME X399-A, BIOS 0808 10/12/2018 >> [11176.741165] Call Trace: >> [11176.741169] <IRQ> >> [11176.741173] dump_stack_lvl+0x5b/0x74 >> [11176.741181] dump_stack+0x10/0x12 >> [11176.741186] __lock_acquire.cold+0x208/0x2df >> [11176.741197] lock_acquire+0xc6/0x2d0 >> [11176.741204] ? dma_fence_signal+0x28/0x80 >> [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 >> [11176.741219] ? dma_fence_signal+0x28/0x80 >> [11176.741225] dma_fence_signal+0x28/0x80 >> [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] >> [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 [gpu_sched] >> [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 >> [11176.741254] dma_fence_signal+0x3b/0x80 >> [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] >> [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] >> [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] >> [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 >> [11176.741290] dma_fence_signal+0x3b/0x80 >> [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] >> [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] >> [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] >> [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] >> [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] >> [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 >> [11176.742402] handle_irq_event_percpu+0x33/0x80 >> [11176.742408] handle_irq_event+0x39/0x60 >> [11176.742414] handle_edge_irq+0x93/0x1d0 >> [11176.742419] __common_interrupt+0x50/0xe0 >> [11176.742426] common_interrupt+0x80/0x90 >> [11176.742431] </IRQ> >> [11176.742436] asm_common_interrupt+0x1e/0x40 >> [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 >> [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 >> ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff >> fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c >> 2b 75 c8 48 8d 14 40 48 8d >> [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 >> [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 RCX: >> 0000000000000000 >> [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 RDI: >> ffffffff9efeed78 >> [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 R09: >> 0000000000000001 >> [11176.742473] R10: 0000000000000001 R11: 0000000000000001 R12: >> ffff9c3350b0e800 >> [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 R15: >> 0000000000000002 >> [11176.742483] ? cpuidle_enter_state+0xf8/0x470 >> [11176.742489] ? cpuidle_enter_state+0xf8/0x470 >> [11176.742495] cpuidle_enter+0x2e/0x40 >> [11176.742500] call_cpuidle+0x23/0x40 >> [11176.742506] do_idle+0x201/0x280 >> [11176.742512] cpu_startup_entry+0x20/0x30 >> [11176.742517] start_secondary+0x11f/0x160 >> [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb >>
On 2021-10-26 6:54 a.m., Christian König wrote:
Am 26.10.21 um 04:33 schrieb Andrey Grodzovsky:
On 2021-10-25 3:56 p.m., Christian König wrote:
In general I'm all there to get this fixed, but there is one major problem: Drivers don't expect the lock to be dropped.
I am probably missing something but in my approach we only modify the code for those clients that call dma_fence_signal, not dma_fence_signal_locked. In those cases the drivers are agnostic to lock behavior (or should be at least) since the lock is acquired within the dma fence code. Note that if you are worried about calling the callback without lock then same exact concern is relevant to using the irq_work directly in the fence code since the irq_work will execute at a later time without locked fence->lock (which is the point of using irq_work).
Yeah, I've seen that it just doesn't make much sense to me.
Not clear what doesn't make sense ?
What we could do is to change all drivers so they call always call the dma_fence_signal functions and drop the _locked variants. This way we could move calling the callback out of the spinlock.
But that requires audit of all drivers, so quite a lot of work to do.
As i said earlier - if we only modify dma_fence_signal and don't touch dma_fence_signal_locked then our only concern should the users of dma_fence_signal.
Yes, but what do you do with the drivers who call the _locked variant?
IMHO we don't touch them at all, they stay as is, we only re-implement dma_fence_signal because drivers that use the locked variant take the lock explicitly and so they intend for their callbacks to run under the lock and if they don't , it's their own problem within their code and they should fix it locally there. Driver that call dma_fence_signal are our only problem because they didn't take the lock explicitly but were forced to run the callback under lock by the dma-fence framework and that something we can change.
Let me please know if I am still missing some point of yours.
Well, I mean we need to be able to handle this for all drivers.
For sure, but as i said above in my opinion we need to change only for those drivers that don't use the _locked version.
Andrey
Regards, Christian.
Andrey
Regards, Christian.
Am 25.10.21 um 21:10 schrieb Andrey Grodzovsky:
Adding back Daniel (somehow he got off the addresses list) and Chris who worked a lot in this area.
On 2021-10-21 2:34 a.m., Christian König wrote:
Am 20.10.21 um 21:32 schrieb Andrey Grodzovsky:
On 2021-10-04 4:14 a.m., Christian König wrote:
> The problem is a bit different. > > The callback is on the dependent fence, while we need to signal > the scheduler fence. > > Daniel is right that this needs an irq_work struct to handle > this properly. > > Christian.
So we had some discussions with Christian regarding irq_work and agreed I should look into doing it but stepping back for a sec -
Why we insist on calling the dma_fence_cb with fence->lock locked ? Is it because of dma_fence_add_callback ? Because we first test for DMA_FENCE_FLAG_SIGNALED_BIT and only after that lock the fence->lock ? If so, can't we move DMA_FENCE_FLAG_SIGNALED_BIT check inside the locked section ? Because if in theory we could call the cb with unlocked fence->lock (i.e. this kind of iteration https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir.boo...) we wouldn't have the lockdep splat. And in general, is it really the correct approach to call a third party code from a call back with locked spinlock ? We don't know what the cb does inside and I don't see any explicit restrictions in documentation of dma_fence_func_t what can and cannot be done there.
Yeah, that's exactly what I meant with using the irq_work directly in the fence code.
My idea is not to use irq work at all but instead to implement unlocked dma_fence cb execution using iteration which drops the spinlock each time next cb is executed and acquiring it again after (until cb_list is empy).
The problem is dma_fence_signal_locked() which is used by quite a number of drivers to signal the fence while holding the lock.
For this I think we should not reuse dma_fence_signal_locked inside dma_fence_signal and instead implement it using the unlocked iteration I mentioned above. I looked a bit in the code and the history and I see that until some time ago (this commit by Chris 0fc89b6802ba1fcc561b0c906e0cefd384e3b2e5), indeed dma_fence_signal was doing it's own, locked iteration and wasn't reusing dma_fence_signal_locked. This way whoever relies on the dma_fence_signal_locked won't be impacted an who is not (like us in drm_sched_fence_scheduled/drm_sched_fence_finished) should also not be impacted by more narrow scope of the lock. I also looked at dma_fence_default_wait and how it locks the fence->lock and check if fence is signaled before wait start and I don't see a problem there either.
I attached quick draft of this proposal to clarify.
Andrey
Otherwise we could indeed simplify the fence handling a lot.
Christian.
Andrey
> > Am 01.10.21 um 17:10 schrieb Andrey Grodzovsky: >> From what I see here you supposed to have actual deadlock and >> not only warning, sched_fence->finished is first signaled from >> within >> hw fence done callback (drm_sched_job_done_cb) but then again >> from within it's own callback (drm_sched_entity_kill_jobs_cb) >> and so >> looks like same fence object is recursively signaled twice. >> This leads to attempt to lock fence->lock second time while >> it's already >> locked. I don't see a need to call drm_sched_fence_finished >> from within drm_sched_entity_kill_jobs_cb as this callback >> already registered >> on sched_fence->finished fence (entity->last_scheduled == >> s_fence->finished) and hence the signaling already took place. >> >> Andrey >> >> On 2021-10-01 6:50 a.m., Christian König wrote: >>> Hey, Andrey. >>> >>> while investigating some memory management problems I've got >>> the logdep splat below. >>> >>> Looks like something is wrong with >>> drm_sched_entity_kill_jobs_cb(), can you investigate? >>> >>> Thanks, >>> Christian. >>> >>> [11176.741052] ============================================ >>> [11176.741056] WARNING: possible recursive locking detected >>> [11176.741060] 5.15.0-rc1-00031-g9d546d600800 #171 Not tainted >>> [11176.741066] -------------------------------------------- >>> [11176.741070] swapper/12/0 is trying to acquire lock: >>> [11176.741074] ffff9c337ed175a8 (&fence->lock){-.-.}-{3:3}, >>> at: dma_fence_signal+0x28/0x80 >>> [11176.741088] >>> but task is already holding lock: >>> [11176.741092] ffff9c337ed172a8 (&fence->lock){-.-.}-{3:3}, >>> at: dma_fence_signal+0x28/0x80 >>> [11176.741100] >>> other info that might help us debug this: >>> [11176.741104] Possible unsafe locking scenario: >>> >>> [11176.741108] CPU0 >>> [11176.741110] ---- >>> [11176.741113] lock(&fence->lock); >>> [11176.741118] lock(&fence->lock); >>> [11176.741122] >>> *** DEADLOCK *** >>> >>> [11176.741125] May be due to missing lock nesting notation >>> >>> [11176.741128] 2 locks held by swapper/12/0: >>> [11176.741133] #0: ffff9c339c30f768 >>> (&ring->fence_drv.lock){-.-.}-{3:3}, at: >>> dma_fence_signal+0x28/0x80 >>> [11176.741142] #1: ffff9c337ed172a8 >>> (&fence->lock){-.-.}-{3:3}, at: dma_fence_signal+0x28/0x80 >>> [11176.741151] >>> stack backtrace: >>> [11176.741155] CPU: 12 PID: 0 Comm: swapper/12 Not tainted >>> 5.15.0-rc1-00031-g9d546d600800 #171 >>> [11176.741160] Hardware name: System manufacturer System >>> Product Name/PRIME X399-A, BIOS 0808 10/12/2018 >>> [11176.741165] Call Trace: >>> [11176.741169] <IRQ> >>> [11176.741173] dump_stack_lvl+0x5b/0x74 >>> [11176.741181] dump_stack+0x10/0x12 >>> [11176.741186] __lock_acquire.cold+0x208/0x2df >>> [11176.741197] lock_acquire+0xc6/0x2d0 >>> [11176.741204] ? dma_fence_signal+0x28/0x80 >>> [11176.741212] _raw_spin_lock_irqsave+0x4d/0x70 >>> [11176.741219] ? dma_fence_signal+0x28/0x80 >>> [11176.741225] dma_fence_signal+0x28/0x80 >>> [11176.741230] drm_sched_fence_finished+0x12/0x20 [gpu_sched] >>> [11176.741240] drm_sched_entity_kill_jobs_cb+0x1c/0x50 >>> [gpu_sched] >>> [11176.741248] dma_fence_signal_timestamp_locked+0xac/0x1a0 >>> [11176.741254] dma_fence_signal+0x3b/0x80 >>> [11176.741260] drm_sched_fence_finished+0x12/0x20 [gpu_sched] >>> [11176.741268] drm_sched_job_done.isra.0+0x7f/0x1a0 [gpu_sched] >>> [11176.741277] drm_sched_job_done_cb+0x12/0x20 [gpu_sched] >>> [11176.741284] dma_fence_signal_timestamp_locked+0xac/0x1a0 >>> [11176.741290] dma_fence_signal+0x3b/0x80 >>> [11176.741296] amdgpu_fence_process+0xd1/0x140 [amdgpu] >>> [11176.741504] sdma_v4_0_process_trap_irq+0x8c/0xb0 [amdgpu] >>> [11176.741731] amdgpu_irq_dispatch+0xce/0x250 [amdgpu] >>> [11176.741954] amdgpu_ih_process+0x81/0x100 [amdgpu] >>> [11176.742174] amdgpu_irq_handler+0x26/0xa0 [amdgpu] >>> [11176.742393] __handle_irq_event_percpu+0x4f/0x2c0 >>> [11176.742402] handle_irq_event_percpu+0x33/0x80 >>> [11176.742408] handle_irq_event+0x39/0x60 >>> [11176.742414] handle_edge_irq+0x93/0x1d0 >>> [11176.742419] __common_interrupt+0x50/0xe0 >>> [11176.742426] common_interrupt+0x80/0x90 >>> [11176.742431] </IRQ> >>> [11176.742436] asm_common_interrupt+0x1e/0x40 >>> [11176.742442] RIP: 0010:cpuidle_enter_state+0xff/0x470 >>> [11176.742449] Code: 0f a3 05 04 54 24 01 0f 82 70 02 00 00 31 >>> ff e8 37 5d 6f ff 80 7d d7 00 0f 85 e9 01 00 00 e8 58 a2 7f ff >>> fb 66 0f 1f 44 00 00 <45> 85 ff 0f 88 01 01 00 00 49 63 c7 4c >>> 2b 75 c8 48 8d 14 40 48 8d >>> [11176.742455] RSP: 0018:ffffb6970021fe48 EFLAGS: 00000202 >>> [11176.742461] RAX: 000000000059be25 RBX: 0000000000000002 >>> RCX: 0000000000000000 >>> [11176.742465] RDX: 0000000000000000 RSI: 0000000000000000 >>> RDI: ffffffff9efeed78 >>> [11176.742470] RBP: ffffb6970021fe80 R08: 0000000000000001 >>> R09: 0000000000000001 >>> [11176.742473] R10: 0000000000000001 R11: 0000000000000001 >>> R12: ffff9c3350b0e800 >>> [11176.742477] R13: ffffffffa00e9680 R14: 00000a2a49ada060 >>> R15: 0000000000000002 >>> [11176.742483] ? cpuidle_enter_state+0xf8/0x470 >>> [11176.742489] ? cpuidle_enter_state+0xf8/0x470 >>> [11176.742495] cpuidle_enter+0x2e/0x40 >>> [11176.742500] call_cpuidle+0x23/0x40 >>> [11176.742506] do_idle+0x201/0x280 >>> [11176.742512] cpu_startup_entry+0x20/0x30 >>> [11176.742517] start_secondary+0x11f/0x160 >>> [11176.742523] secondary_startup_64_no_verify+0xb0/0xbb >>> >
Am 27.10.21 um 16:27 schrieb Andrey Grodzovsky:
[SNIP]
Let me please know if I am still missing some point of yours.
Well, I mean we need to be able to handle this for all drivers.
For sure, but as i said above in my opinion we need to change only for those drivers that don't use the _locked version.
And that absolutely won't work.
See the dma_fence is a contract between drivers, so you need the same calling convention between all drivers.
Either we always call the callback with the lock held or we always call it without the lock, but sometimes like that and sometimes otherwise won't work.
Christian.
Andrey
On 2021-10-27 10:34 a.m., Christian König wrote:
Am 27.10.21 um 16:27 schrieb Andrey Grodzovsky:
[SNIP]
Let me please know if I am still missing some point of yours.
Well, I mean we need to be able to handle this for all drivers.
For sure, but as i said above in my opinion we need to change only for those drivers that don't use the _locked version.
And that absolutely won't work.
See the dma_fence is a contract between drivers, so you need the same calling convention between all drivers.
Either we always call the callback with the lock held or we always call it without the lock, but sometimes like that and sometimes otherwise won't work.
Christian.
I am not sure I fully understand what problems this will cause but anyway, then we are back to irq_work. We cannot embed irq_work as union within dma_fenc's cb_list because it's already reused as timestamp and as rcu head after the fence is signaled. So I will do it within drm_scheduler with single irq_work per drm_sched_entity as we discussed before.
Andrey
Andrey
Am 27.10.21 um 16:47 schrieb Andrey Grodzovsky:
On 2021-10-27 10:34 a.m., Christian König wrote:
Am 27.10.21 um 16:27 schrieb Andrey Grodzovsky:
[SNIP]
Let me please know if I am still missing some point of yours.
Well, I mean we need to be able to handle this for all drivers.
For sure, but as i said above in my opinion we need to change only for those drivers that don't use the _locked version.
And that absolutely won't work.
See the dma_fence is a contract between drivers, so you need the same calling convention between all drivers.
Either we always call the callback with the lock held or we always call it without the lock, but sometimes like that and sometimes otherwise won't work.
Christian.
I am not sure I fully understand what problems this will cause but anyway, then we are back to irq_work. We cannot embed irq_work as union within dma_fenc's cb_list because it's already reused as timestamp and as rcu head after the fence is signaled. So I will do it within drm_scheduler with single irq_work per drm_sched_entity as we discussed before.
That won't work either. We free up the entity after the cleanup function. That's the reason we use the callback on the job in the first place.
We could overlead the cb structure in the job though.
Christian.
Andrey
Andrey
On 2021-10-27 10:50 a.m., Christian König wrote:
Am 27.10.21 um 16:47 schrieb Andrey Grodzovsky:
On 2021-10-27 10:34 a.m., Christian König wrote:
Am 27.10.21 um 16:27 schrieb Andrey Grodzovsky:
[SNIP]
Let me please know if I am still missing some point of yours.
Well, I mean we need to be able to handle this for all drivers.
For sure, but as i said above in my opinion we need to change only for those drivers that don't use the _locked version.
And that absolutely won't work.
See the dma_fence is a contract between drivers, so you need the same calling convention between all drivers.
Either we always call the callback with the lock held or we always call it without the lock, but sometimes like that and sometimes otherwise won't work.
Christian.
I am not sure I fully understand what problems this will cause but anyway, then we are back to irq_work. We cannot embed irq_work as union within dma_fenc's cb_list because it's already reused as timestamp and as rcu head after the fence is signaled. So I will do it within drm_scheduler with single irq_work per drm_sched_entity as we discussed before.
That won't work either. We free up the entity after the cleanup function. That's the reason we use the callback on the job in the first place.
Yep, missed it.
We could overlead the cb structure in the job though.
I guess, since no one else is using this member it after the cb executed.
Andrey
Christian.
Andrey
Andrey
On 2021-10-27 3:58 p.m., Andrey Grodzovsky wrote:
On 2021-10-27 10:50 a.m., Christian König wrote:
Am 27.10.21 um 16:47 schrieb Andrey Grodzovsky:
On 2021-10-27 10:34 a.m., Christian König wrote:
Am 27.10.21 um 16:27 schrieb Andrey Grodzovsky:
[SNIP]
> Let me please know if I am still missing some point of yours.
Well, I mean we need to be able to handle this for all drivers.
For sure, but as i said above in my opinion we need to change only for those drivers that don't use the _locked version.
And that absolutely won't work.
See the dma_fence is a contract between drivers, so you need the same calling convention between all drivers.
Either we always call the callback with the lock held or we always call it without the lock, but sometimes like that and sometimes otherwise won't work.
Christian.
I am not sure I fully understand what problems this will cause but anyway, then we are back to irq_work. We cannot embed irq_work as union within dma_fenc's cb_list because it's already reused as timestamp and as rcu head after the fence is signaled. So I will do it within drm_scheduler with single irq_work per drm_sched_entity as we discussed before.
That won't work either. We free up the entity after the cleanup function. That's the reason we use the callback on the job in the first place.
Yep, missed it.
We could overlead the cb structure in the job though.
I guess, since no one else is using this member it after the cb executed.
Andrey
Attached a patch. Give it a try please, I tested it on my side and tried to generate the right conditions to trigger this code path by repeatedly submitting commands while issuing GPU reset to stop the scheduler and then killing command submissions process in the middle. But for some reason looks like the job_queue was always empty already at the time of entity kill.
Andrey
Christian.
Andrey
Andrey
Am 28.10.21 um 19:26 schrieb Andrey Grodzovsky:
On 2021-10-27 3:58 p.m., Andrey Grodzovsky wrote:
On 2021-10-27 10:50 a.m., Christian König wrote:
Am 27.10.21 um 16:47 schrieb Andrey Grodzovsky:
On 2021-10-27 10:34 a.m., Christian König wrote:
Am 27.10.21 um 16:27 schrieb Andrey Grodzovsky:
[SNIP] > >> Let me please know if I am still missing some point of yours. > > Well, I mean we need to be able to handle this for all drivers.
For sure, but as i said above in my opinion we need to change only for those drivers that don't use the _locked version.
And that absolutely won't work.
See the dma_fence is a contract between drivers, so you need the same calling convention between all drivers.
Either we always call the callback with the lock held or we always call it without the lock, but sometimes like that and sometimes otherwise won't work.
Christian.
I am not sure I fully understand what problems this will cause but anyway, then we are back to irq_work. We cannot embed irq_work as union within dma_fenc's cb_list because it's already reused as timestamp and as rcu head after the fence is signaled. So I will do it within drm_scheduler with single irq_work per drm_sched_entity as we discussed before.
That won't work either. We free up the entity after the cleanup function. That's the reason we use the callback on the job in the first place.
Yep, missed it.
We could overlead the cb structure in the job though.
I guess, since no one else is using this member it after the cb executed.
Andrey
Attached a patch. Give it a try please, I tested it on my side and tried to generate the right conditions to trigger this code path by repeatedly submitting commands while issuing GPU reset to stop the scheduler and then killing command submissions process in the middle. But for some reason looks like the job_queue was always empty already at the time of entity kill.
It was trivial to trigger with the stress utility I've hacked together:
amdgpu_stress -b v 1g -b g 1g -c 1 2 1g 1k
Then while it is copying just cntrl+c to kill it.
The patch itself is:
Tested-by: Christian König christian.koenig@amd.com Reviewed-by: Christian König christian.koenig@amd.com
Thanks, Christian.
Andrey
Christian.
Andrey
Andrey
Pushed to drm-misc-next
Andrey
On 2021-10-29 3:07 a.m., Christian König wrote:
Attached a patch. Give it a try please, I tested it on my side and tried to generate the right conditions to trigger this code path by repeatedly submitting commands while issuing GPU reset to stop the scheduler and then killing command submissions process in the middle. But for some reason looks like the job_queue was always empty already at the time of entity kill.
It was trivial to trigger with the stress utility I've hacked together:
amdgpu_stress -b v 1g -b g 1g -c 1 2 1g 1k
Then while it is copying just cntrl+c to kill it.
The patch itself is:
Tested-by: Christian König christian.koenig@amd.com Reviewed-by: Christian König christian.koenig@amd.com
Thanks, Christian.
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