drm/i915: Complete the fences as they are cancelled due to wedging

We inspect the requests under the assumption that they will be marked as
completed when they are removed from the queue. Currently however, in the
process of wedging the requests will be removed from the queue before they
are completed, so rearrange the code to complete the fences before the
locks are dropped.

<1>[  354.473346] BUG: unable to handle kernel NULL pointer dereference at 0000000000000250
<6>[  354.473363] PGD 0 P4D 0
<4>[  354.473370] Oops: 0000 [#1] PREEMPT SMP PTI
<4>[  354.473380] CPU: 0 PID: 4470 Comm: gem_eio Tainted: G     U            4.20.0-rc4-CI-CI_DRM_5216+ #1
<4>[  354.473393] Hardware name: Intel Corporation NUC7CJYH/NUC7JYB, BIOS JYGLKCPX.86A.0027.2018.0125.1347 01/25/2018
<4>[  354.473480] RIP: 0010:__i915_schedule+0x311/0x5e0 [i915]
<4>[  354.473490] Code: 49 89 44 24 20 4d 89 4c 24 28 4d 89 29 44 39 b3 a0 04 00 00 7d 3a 41 8b 44 24 78 85 c0 74 13 48 8b 93 78 04 00 00 48 83 e2 fc <39> 82 50 02 00 00 79 1e 44 89 b3 a0 04 00 00 48 8d bb d0 03 00 00
<4>[  354.473515] RSP: 0018:ffffc900001bba90 EFLAGS: 00010046
<4>[  354.473524] RAX: 0000000000000003 RBX: ffff8882624c8008 RCX: f34a737800000000
<4>[  354.473535] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8882624c8048
<4>[  354.473545] RBP: ffffc900001bbab0 R08: 000000005963f1f1 R09: 0000000000000000
<4>[  354.473556] R10: ffffc900001bba10 R11: ffff8882624c8060 R12: ffff88824fdd7b98
<4>[  354.473567] R13: ffff88824fdd7bb8 R14: 0000000000000001 R15: ffff88824fdd7750
<4>[  354.473578] FS:  00007f44b4b5b980(0000) GS:ffff888277e00000(0000) knlGS:0000000000000000
<4>[  354.473590] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[  354.473599] CR2: 0000000000000250 CR3: 000000026976e000 CR4: 0000000000340ef0
<4>[  354.473611] Call Trace:
<4>[  354.473622]  ? lock_acquire+0xa6/0x1c0
<4>[  354.473677]  ? i915_schedule_bump_priority+0x57/0xd0 [i915]
<4>[  354.473736]  i915_schedule_bump_priority+0x72/0xd0 [i915]
<4>[  354.473792]  i915_request_wait+0x4db/0x840 [i915]
<4>[  354.473804]  ? get_pwq.isra.4+0x2c/0x50
<4>[  354.473813]  ? ___preempt_schedule+0x16/0x18
<4>[  354.473824]  ? wake_up_q+0x70/0x70
<4>[  354.473831]  ? wake_up_q+0x70/0x70
<4>[  354.473882]  ? gen6_rps_boost+0x118/0x120 [i915]
<4>[  354.473936]  i915_gem_object_wait_fence+0x8a/0x110 [i915]
<4>[  354.473991]  i915_gem_object_wait+0x113/0x500 [i915]
<4>[  354.474047]  i915_gem_wait_ioctl+0x11c/0x2f0 [i915]
<4>[  354.474101]  ? i915_gem_unset_wedged+0x210/0x210 [i915]
<4>[  354.474113]  drm_ioctl_kernel+0x81/0xf0
<4>[  354.474123]  drm_ioctl+0x2de/0x390
<4>[  354.474175]  ? i915_gem_unset_wedged+0x210/0x210 [i915]
<4>[  354.474187]  ? finish_task_switch+0x95/0x260
<4>[  354.474197]  ? lock_acquire+0xa6/0x1c0
<4>[  354.474207]  do_vfs_ioctl+0xa0/0x6e0
<4>[  354.474217]  ? __fget+0xfc/0x1e0
<4>[  354.474225]  ksys_ioctl+0x35/0x60
<4>[  354.474233]  __x64_sys_ioctl+0x11/0x20
<4>[  354.474241]  do_syscall_64+0x55/0x190
<4>[  354.474251]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
<4>[  354.474260] RIP: 0033:0x7f44b3de65d7
<4>[  354.474267] Code: b3 66 90 48 8b 05 b1 48 2d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 81 48 2d 00 f7 d8 64 89 01 48
<4>[  354.474293] RSP: 002b:00007fff974948e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
<4>[  354.474305] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f44b3de65d7
<4>[  354.474316] RDX: 00007fff97494940 RSI: 00000000c010646c RDI: 0000000000000007
<4>[  354.474327] RBP: 00007fff97494940 R08: 0000000000000000 R09: 00007f44b40bbc40
<4>[  354.474337] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000c010646c
<4>[  354.474348] R13: 0000000000000007 R14: 0000000000000000 R15: 0000000000000000

v2: Avoid floating requests.
v3: Can't call dma_fence_signal() under the timeline lock!
v4: Can't call dma_fence_signal() from inside another fence either.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181203113701.12106-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -3308,16 +3308,6 @@ void i915_gem_reset_finish(struct drm_i915_private *dev_priv)
 }
 
 static void nop_submit_request(struct i915_request *request)
-{
-	GEM_TRACE("%s fence %llx:%d -> -EIO\n",
-		  request->engine->name,
-		  request->fence.context, request->fence.seqno);
-	dma_fence_set_error(&request->fence, -EIO);
-
-	i915_request_submit(request);
-}
-
-static void nop_complete_submit_request(struct i915_request *request)
 {
 	unsigned long flags;
 
@@ -3354,57 +3344,33 @@ void i915_gem_set_wedged(struct drm_i915_private *i915)
 	 * rolling the global seqno forward (since this would complete requests
 	 * for which we haven't set the fence error to EIO yet).
 	 */
-	for_each_engine(engine, i915, id) {
+	for_each_engine(engine, i915, id)
 		i915_gem_reset_prepare_engine(engine);
 
-		engine->submit_request = nop_submit_request;
-		engine->schedule = NULL;
-	}
-	i915->caps.scheduler = 0;
-
 	/* Even if the GPU reset fails, it should still stop the engines */
 	if (INTEL_GEN(i915) >= 5)
 		intel_gpu_reset(i915, ALL_ENGINES);
 
-	/*
-	 * Make sure no one is running the old callback before we proceed with
-	 * cancelling requests and resetting the completion tracking. Otherwise
-	 * we might submit a request to the hardware which never completes.
-	 */
-	synchronize_rcu();
-
 	for_each_engine(engine, i915, id) {
-		/* Mark all executing requests as skipped */
-		engine->cancel_requests(engine);
-
-		/*
-		 * Only once we've force-cancelled all in-flight requests can we
-		 * start to complete all requests.
-		 */
-		engine->submit_request = nop_complete_submit_request;
+		engine->submit_request = nop_submit_request;
+		engine->schedule = NULL;
 	}
+	i915->caps.scheduler = 0;
 
 	/*
 	 * Make sure no request can slip through without getting completed by
 	 * either this call here to intel_engine_init_global_seqno, or the one
-	 * in nop_complete_submit_request.
+	 * in nop_submit_request.
 	 */
 	synchronize_rcu();
 
-	for_each_engine(engine, i915, id) {
-		unsigned long flags;
-
-		/*
-		 * Mark all pending requests as complete so that any concurrent
-		 * (lockless) lookup doesn't try and wait upon the request as we
-		 * reset it.
-		 */
-		spin_lock_irqsave(&engine->timeline.lock, flags);
-		intel_engine_init_global_seqno(engine,
-					       intel_engine_last_submit(engine));
-		spin_unlock_irqrestore(&engine->timeline.lock, flags);
+	/* Mark all executing requests as skipped */
+	for_each_engine(engine, i915, id)
+		engine->cancel_requests(engine);
 
+	for_each_engine(engine, i915, id) {
 		i915_gem_reset_finish_engine(engine);
+		intel_engine_wakeup(engine);
 	}
 
 out:

drivers/gpu/drm/i915/intel_lrc.c

@@ -820,7 +820,10 @@ static void execlists_cancel_requests(struct intel_engine_cs *engine)
 	/* Mark all executing requests as skipped. */
 	list_for_each_entry(rq, &engine->timeline.requests, link) {
 		GEM_BUG_ON(!rq->global_seqno);
-		if (!i915_request_completed(rq))
+
+		if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &rq->fence.flags))
+			continue;
+
 		dma_fence_set_error(&rq->fence, -EIO);
 	}
 
@@ -841,6 +844,10 @@ static void execlists_cancel_requests(struct intel_engine_cs *engine)
 			kmem_cache_free(engine->i915->priorities, p);
 	}
 
+	intel_write_status_page(engine,
+				I915_GEM_HWS_INDEX,
+				intel_engine_last_submit(engine));
+
 	/* Remaining _unready_ requests will be nop'ed when submitted */
 
 	execlists->queue_priority = INT_MIN;

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -755,9 +755,18 @@ static void cancel_requests(struct intel_engine_cs *engine)
 	/* Mark all submitted requests as skipped. */
 	list_for_each_entry(request, &engine->timeline.requests, link) {
 		GEM_BUG_ON(!request->global_seqno);
-		if (!i915_request_completed(request))
+
+		if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
+			     &request->fence.flags))
+			continue;
+
 		dma_fence_set_error(&request->fence, -EIO);
 	}
+
+	intel_write_status_page(engine,
+				I915_GEM_HWS_INDEX,
+				intel_engine_last_submit(engine));
+
 	/* Remaining _unready_ requests will be nop'ed when submitted */
 
 	spin_unlock_irqrestore(&engine->timeline.lock, flags);