drm/i915: Suspend submission tasklets around wedging

After staring hard at sequences like

[   28.199013]  systemd-1       2..s. 26062228us : execlists_submission_tasklet: rcs0 cs-irq head=0 [0?], tail=1 [1?]
[   28.199095]  systemd-1       2..s. 26062229us : execlists_submission_tasklet: rcs0 csb[1]: status=0x00000018:0x00000000, active=0x1
[   28.199177]  systemd-1       2..s. 26062230us : execlists_submission_tasklet: rcs0 out[0]: ctx=0.1, seqno=3, prio=-1024
[   28.199258]  systemd-1       2..s. 26062231us : execlists_submission_tasklet: rcs0 completed ctx=0
[   28.199340]  gem_eio-829     1..s1 26066853us : execlists_submission_tasklet: rcs0 in[0]:  ctx=1.1, seqno=1, prio=0
[   28.199421]   <idle>-0       2..s. 26066863us : execlists_submission_tasklet: rcs0 cs-irq head=1 [1?], tail=2 [2?]
[   28.199503]   <idle>-0       2..s. 26066865us : execlists_submission_tasklet: rcs0 csb[2]: status=0x00000001:0x00000000, active=0x1
[   28.199585]  gem_eio-829     1..s1 26067077us : execlists_submission_tasklet: rcs0 in[1]:  ctx=3.1, seqno=2, prio=0
[   28.199667]  gem_eio-829     1..s1 26067078us : execlists_submission_tasklet: rcs0 in[0]:  ctx=1.2, seqno=1, prio=0
[   28.199749]   <idle>-0       2..s. 26067084us : execlists_submission_tasklet: rcs0 cs-irq head=2 [2?], tail=3 [3?]
[   28.199830]   <idle>-0       2..s. 26067085us : execlists_submission_tasklet: rcs0 csb[3]: status=0x00008002:0x00000001, active=0x1
[   28.199912]   <idle>-0       2..s. 26067086us : execlists_submission_tasklet: rcs0 out[0]: ctx=1.2, seqno=1, prio=0
[   28.199994]  gem_eio-829     2..s. 28246084us : execlists_submission_tasklet: rcs0 cs-irq head=3 [3?], tail=4 [4?]
[   28.200096]  gem_eio-829     2..s. 28246088us : execlists_submission_tasklet: rcs0 csb[4]: status=0x00000014:0x00000001, active=0x5
[   28.200178]  gem_eio-829     2..s. 28246089us : execlists_submission_tasklet: rcs0 out[0]: ctx=0.0, seqno=0, prio=0
[   28.200260]  gem_eio-829     2..s. 28246127us : execlists_submission_tasklet: execlists_submission_tasklet:886 GEM_BUG_ON(buf[2 * head + 1] != port->context_id)

the conclusion is that the only place where the ports are reset to zero,
is from engine->cancel_requests called during i915_gem_set_wedged().

The race is horrible as it results from calling set-wedged on active HW
(the GPU reset failed) and as such we need to be careful as the HW state
changes beneath us. Fortunately, it's the same scary conditions as
affect normal reset, so we can reuse the same machinery to disable state
tracking as we clobber it.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104945
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Fixes: af7a8ffad9c5 ("drm/i915: Use rcu instead of stop_machine in set_wedged")
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180302113324.23189-2-chris@chris-wilson.co.uk

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c29b1a1cbe96..dcdcc09240b9 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3212,8 +3212,10 @@ 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;
+	}
 
 	/*
 	 * Make sure no one is running the old callback before we proceed with
@@ -3255,6 +3257,8 @@ void i915_gem_set_wedged(struct drm_i915_private *i915)
 		intel_engine_init_global_seqno(engine,
 					       intel_engine_last_submit(engine));
 		spin_unlock_irqrestore(&engine->timeline->lock, flags);
+
+		i915_gem_reset_finish_engine(engine);
 	}
 
 	wake_up_all(&i915->gpu_error.reset_queue);