On Fri, 23 Dec 2016, changbin.du@intel.com wrote:

From: "Du, Changbin" changbin.du@intel.com

This patch fix a crash in function reset_common_ring. In this case, the port[0].request is null when reset the render ring, so a null dereference exception is raised. We need to check execlist_port status first.

[ 35.748034] BUG: unable to handle kernel NULL pointer dereference at 0000000000000070 [ 35.749567] IP: [<ffffffff81521bfe>] reset_common_ring+0xbe/0x150 [ 35.749567] Call Trace: [ 35.749567] [<ffffffff8150ded0>] i915_gem_reset+0x150/0x270 [ 35.749567] [<ffffffff814d3c0a>] i915_reset+0x8a/0xe0 [ 35.749567] [<ffffffff814d8c21>] i915_reset_and_wakeup+0x131/0x160 [ 35.749567] [<ffffffff815298f0>] ? gen5_read8+0x110/0x110 [ 35.749567] [<ffffffff814dc97a>] i915_handle_error+0xca/0x5a0 [ 35.749567] [<ffffffff813bac9d>] ? scnprintf+0x3d/0x70 [ 35.749567] [<ffffffff814dd063>] i915_hangcheck_elapsed+0x213/0x510 [ 35.749567] [<ffffffff810c4c4b>] process_one_work+0x15b/0x470 [ 35.749567] [<ffffffff810c4fa3>] worker_thread+0x43/0x4d0 [ 35.749567] [<ffffffff810c4f60>] ? process_one_work+0x470/0x470 [ 35.749567] [<ffffffff810c4f60>] ? process_one_work+0x470/0x470 [ 35.749567] [<ffffffff810c103e>] ? call_usermodehelper_exec_async+0x12e/0x130 [ 35.749567] [<ffffffff810ca1a5>] kthread+0xc5/0xe0 [ 35.749567] [<ffffffff810ca0e0>] ? kthread_park+0x60/0x60 [ 35.749567] [<ffffffff810c0f10>] ? umh_complete+0x40/0x40 [ 35.749567] [<ffffffff81a35392>] ret_from_fork+0x22/0x30

Fixes: ?

i.e. which commit broke things?

BR, Jani.

Signed-off-by: Changbin Du changbin.du@intel.com

drivers/gpu/drm/i915/intel_lrc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 0a09024..81a9b0b 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -1450,7 +1450,7 @@ static void reset_common_ring(struct intel_engine_cs *engine,

/* Catch up with any missed context-switch interrupts */ I915_WRITE(RING_CONTEXT_STATUS_PTR(engine), _MASKED_FIELD(0xffff, 0));

• if (request->ctx != port[0].request->ctx) {

• if (!execlists_elsp_idle(engine) && request->ctx != port[0].request->ctx) { i915_gem_request_put(port[0].request); port[0] = port[1]; memset(&port[1], 0, sizeof(port[1]));