Start introducing a new part of the framework for handling user fences.
In strict opposition to normal fences user fences don't reliable finish in a fixed amount of time and therefore can't be used as dependency in memory management.
Because of this user fences are marked with DMA_FENCE_FLAG_USER. Lockdep is checked that we can at least fault user pages when we check them for signaling.
This patch also adds a flag to dma_fence_get_stub() so that we can retrieve a signaled user fence. This can be used together with lockdep to test the handling in code path supporting user fences.
Signed-off-by: Christian König christian.koenig@amd.com --- drivers/dma-buf/dma-fence-unwrap.c | 4 +-- drivers/dma-buf/dma-fence.c | 31 ++++++++++++------- drivers/dma-buf/st-dma-fence.c | 2 +- .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 2 +- drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 2 +- drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c | 2 +- drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 4 +-- drivers/gpu/drm/drm_syncobj.c | 10 +++--- include/linux/dma-fence.h | 17 +++++++++- 9 files changed, 49 insertions(+), 25 deletions(-)
diff --git a/drivers/dma-buf/dma-fence-unwrap.c b/drivers/dma-buf/dma-fence-unwrap.c index c9becc74896d..87ee2efced10 100644 --- a/drivers/dma-buf/dma-fence-unwrap.c +++ b/drivers/dma-buf/dma-fence-unwrap.c @@ -76,7 +76,7 @@ struct dma_fence *__dma_fence_merge(unsigned int num_fences, }
if (count == 0) - return dma_fence_get_stub(); + return dma_fence_get_stub(false);
if (count > INT_MAX) return NULL; @@ -129,7 +129,7 @@ struct dma_fence *__dma_fence_merge(unsigned int num_fences, } while (tmp);
if (count == 0) { - tmp = dma_fence_get_stub(); + tmp = dma_fence_get_stub(false); goto return_tmp; }
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c index 066400ed8841..52873f5eaeba 100644 --- a/drivers/dma-buf/dma-fence.c +++ b/drivers/dma-buf/dma-fence.c @@ -26,6 +26,7 @@ EXPORT_TRACEPOINT_SYMBOL(dma_fence_signaled);
static DEFINE_SPINLOCK(dma_fence_stub_lock); static struct dma_fence dma_fence_stub; +static struct dma_fence dma_fence_user_stub;
/* * fence context counter: each execution context should have its own @@ -123,24 +124,28 @@ static const struct dma_fence_ops dma_fence_stub_ops = {
/** * dma_fence_get_stub - return a signaled fence + * @user: if true the returned fence is an user fence * - * Return a stub fence which is already signaled. The fence's - * timestamp corresponds to the first time after boot this - * function is called. + * Return a stub fence which is already signaled. The fence's timestamp + * corresponds to the first time after boot this function is called. If @user is + * true an user fence is returned which can be used with lockdep to test user + * fence saveness in a code path. */ -struct dma_fence *dma_fence_get_stub(void) +struct dma_fence *dma_fence_get_stub(bool user) { + struct dma_fence *fence = user ? &dma_fence_stub : &dma_fence_user_stub; + spin_lock(&dma_fence_stub_lock); - if (!dma_fence_stub.ops) { - dma_fence_init(&dma_fence_stub, - &dma_fence_stub_ops, - &dma_fence_stub_lock, + if (!fence->ops) { + dma_fence_init(fence, &dma_fence_stub_ops, &dma_fence_stub_lock, 0, 0); - dma_fence_signal_locked(&dma_fence_stub); + if (user) + set_bit(DMA_FENCE_FLAG_USER, &fence->flags); + dma_fence_signal_locked(fence); } spin_unlock(&dma_fence_stub_lock);
- return dma_fence_get(&dma_fence_stub); + return dma_fence_get(fence); } EXPORT_SYMBOL(dma_fence_get_stub);
@@ -497,8 +502,9 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout) return -EINVAL;
might_sleep(); - __dma_fence_might_wait(); + if (test_bit(DMA_FENCE_FLAG_USER, &fence->flags)) + might_fault();
trace_dma_fence_wait_start(fence); if (fence->ops->wait) @@ -870,6 +876,9 @@ dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count, for (i = 0; i < count; ++i) { struct dma_fence *fence = fences[i];
+ if (test_bit(DMA_FENCE_FLAG_USER, &fence->flags)) + might_fault(); + cb[i].task = current; if (dma_fence_add_callback(fence, &cb[i].base, dma_fence_default_wait_cb)) { diff --git a/drivers/dma-buf/st-dma-fence.c b/drivers/dma-buf/st-dma-fence.c index c8a12d7ad71a..50f757f75645 100644 --- a/drivers/dma-buf/st-dma-fence.c +++ b/drivers/dma-buf/st-dma-fence.c @@ -412,7 +412,7 @@ static int test_stub(void *arg) int i;
for (i = 0; i < ARRAY_SIZE(f); i++) { - f[i] = dma_fence_get_stub(); + f[i] = dma_fence_get_stub((i % 2) == 1); if (!dma_fence_is_signaled(f[i])) { pr_err("Obtained unsignaled stub fence!\n"); goto err; diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c index 64ac4f8f49be..541c59635c34 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c @@ -263,7 +263,7 @@ static int amdgpu_amdkfd_remove_eviction_fence(struct amdgpu_bo *bo, /* TODO: Instead of block before we should use the fence of the page * table update and TLB flush here directly. */ - replacement = dma_fence_get_stub(); + replacement = dma_fence_get_stub(false); dma_resv_replace_fences(bo->tbo.base.resv, ef->base.context, replacement, DMA_RESV_USAGE_READ); dma_fence_put(replacement); diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c index a28b7947a034..95eeab527ca9 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c @@ -1399,7 +1399,7 @@ int amdgpu_cs_fence_to_handle_ioctl(struct drm_device *dev, void *data, return PTR_ERR(fence);
if (!fence) - fence = dma_fence_get_stub(); + fence = dma_fence_get_stub(false);
switch (info->in.what) { case AMDGPU_FENCE_TO_HANDLE_GET_SYNCOBJ: diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c index 7f33ae87cb41..73165f387f3b 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c @@ -193,7 +193,7 @@ int amdgpu_ring_init(struct amdgpu_device *adev, struct amdgpu_ring *ring, adev->rings[ring->idx] = ring; ring->num_hw_submission = sched_hw_submission; ring->sched_score = sched_score; - ring->vmid_wait = dma_fence_get_stub(); + ring->vmid_wait = dma_fence_get_stub(false); r = amdgpu_fence_driver_init_ring(ring); if (r) return r; diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c index 7e5cc8323329..e5c8e72a9485 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c @@ -1689,7 +1689,7 @@ int amdgpu_vm_bo_update_mapping(struct amdgpu_device *adev, }
if (!unlocked && !dma_fence_is_signaled(vm->last_unlocked)) { - struct dma_fence *tmp = dma_fence_get_stub(); + struct dma_fence *tmp = dma_fence_get_stub(false);
amdgpu_bo_fence(vm->root.bo, vm->last_unlocked, true); swap(vm->last_unlocked, tmp); @@ -2905,7 +2905,7 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm) else vm->update_funcs = &amdgpu_vm_sdma_funcs; vm->last_update = NULL; - vm->last_unlocked = dma_fence_get_stub(); + vm->last_unlocked = dma_fence_get_stub(false);
mutex_init(&vm->eviction_lock); vm->evicting = false; diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c index 7e48dcd1bee4..5a961ea90a35 100644 --- a/drivers/gpu/drm/drm_syncobj.c +++ b/drivers/gpu/drm/drm_syncobj.c @@ -255,7 +255,7 @@ static void drm_syncobj_fence_add_wait(struct drm_syncobj *syncobj, dma_fence_put(fence); list_add_tail(&wait->node, &syncobj->cb_list); } else if (!fence) { - wait->fence = dma_fence_get_stub(); + wait->fence = dma_fence_get_stub(false); } else { wait->fence = fence; } @@ -411,7 +411,7 @@ int drm_syncobj_find_fence(struct drm_file *file_private, * signalled, use a new fence instead. */ if (!*fence) - *fence = dma_fence_get_stub(); + *fence = dma_fence_get_stub(false);
goto out; } @@ -1000,7 +1000,7 @@ static void syncobj_wait_syncobj_func(struct drm_syncobj *syncobj, dma_fence_put(fence); return; } else if (!fence) { - wait->fence = dma_fence_get_stub(); + wait->fence = dma_fence_get_stub(false); } else { wait->fence = fence; } @@ -1067,7 +1067,7 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs, if (fence) entries[i].fence = fence; else - entries[i].fence = dma_fence_get_stub(); + entries[i].fence = dma_fence_get_stub(false);
if ((flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE) || dma_fence_is_signaled(entries[i].fence)) { @@ -1472,7 +1472,7 @@ drm_syncobj_timeline_signal_ioctl(struct drm_device *dev, void *data, }
for (i = 0; i < args->count_handles; i++) { - struct dma_fence *fence = dma_fence_get_stub(); + struct dma_fence *fence = dma_fence_get_stub(false);
drm_syncobj_add_point(syncobjs[i], chains[i], fence, points[i]); diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h index afea82ec5946..be96687d31d8 100644 --- a/include/linux/dma-fence.h +++ b/include/linux/dma-fence.h @@ -99,6 +99,16 @@ enum dma_fence_flag_bits { DMA_FENCE_FLAG_SIGNALED_BIT, DMA_FENCE_FLAG_TIMESTAMP_BIT, DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, + + /** + * @DMA_FENCE_FLAG_USER: + * + * Indicates an user fence. User fences are not guaranteed to signal in + * a finite amount of time. Because of this it is not allowed to wait for user + * fences with any lock held nor depend the signaling of none user + * fences on them. + */ + DMA_FENCE_FLAG_USER, DMA_FENCE_FLAG_DRIVER, /* must always be last member */ };
@@ -398,6 +408,8 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence); static inline bool dma_fence_is_signaled_locked(struct dma_fence *fence) { + WARN_ON(test_bit(DMA_FENCE_FLAG_USER, &fence->flags)); + if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) return true;
@@ -428,6 +440,9 @@ dma_fence_is_signaled_locked(struct dma_fence *fence) static inline bool dma_fence_is_signaled(struct dma_fence *fence) { + if (test_bit(DMA_FENCE_FLAG_USER, &fence->flags)) + might_fault(); + if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) return true;
@@ -583,7 +598,7 @@ static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr) return ret < 0 ? ret : 0; }
-struct dma_fence *dma_fence_get_stub(void); +struct dma_fence *dma_fence_get_stub(bool user); struct dma_fence *dma_fence_allocate_private_stub(void); u64 dma_fence_context_alloc(unsigned num);