As a virtual engine may change the rq->engine to point to the active
request in flight, we need to warn the compiler that an active request's
engine is volatile.
[ 95.017686] write (marked) to 0xffff8881e8386b10 of 8 bytes by interrupt on cpu 2:
[ 95.018123] execlists_dequeue+0x762/0x2150 [i915]
[ 95.018539] __execlists_submission_tasklet+0x48/0x60 [i915]
[ 95.018955] execlists_submission_tasklet+0xd3/0x170 [i915]
[ 95.018986] tasklet_action_common.isra.0+0x42/0xa0
[ 95.019016] __do_softirq+0xd7/0x2cd
[ 95.019043] irq_exit+0xbe/0xe0
[ 95.019068] irq_work_interrupt+0xf/0x20
[ 95.019491] i915_request_retire+0x2c5/0x670 [i915]
[ 95.019937] retire_requests+0xa1/0xf0 [i915]
[ 95.020348] engine_retire+0xa1/0xe0 [i915]
[ 95.020376] process_one_work+0x3b1/0x690
[ 95.020403] worker_thread+0x80/0x670
[ 95.020429] kthread+0x19a/0x1e0
[ 95.020454] ret_from_fork+0x1f/0x30
[ 95.020476]
[ 95.020498] read to 0xffff8881e8386b10 of 8 bytes by task 8909 on cpu 3:
[ 95.020918] __i915_request_commit+0x177/0x220 [i915]
[ 95.021329] i915_gem_do_execbuffer+0x38c4/0x4e50 [i915]
[ 95.021750] i915_gem_execbuffer2_ioctl+0x2c3/0x580 [i915]
[ 95.021784] drm_ioctl_kernel+0xe4/0x120
[ 95.021809] drm_ioctl+0x297/0x4c7
[ 95.021832] ksys_ioctl+0x89/0xb0
[ 95.021865] __x64_sys_ioctl+0x42/0x60
[ 95.021901] do_syscall_64+0x6e/0x2c0
[ 95.021927] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_request.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 74169671afb5..c0df71d7d0ff 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -977,6 +977,8 @@ emit_semaphore_wait(struct i915_request *to,
struct i915_request *from,
gfp_t gfp)
{
+ const intel_engine_mask_t mask = READ_ONCE(from->engine)->mask;
+
if (!intel_context_use_semaphores(to->context))
goto await_fence;
@@ -984,7 +986,7 @@ emit_semaphore_wait(struct i915_request *to,
goto await_fence;
/* Just emit the first semaphore we see as request space is limited. */
- if (already_busywaiting(to) & from->engine->mask)
+ if (already_busywaiting(to) & mask)
goto await_fence;
if (i915_request_await_start(to, from) < 0)
@@ -997,7 +999,7 @@ emit_semaphore_wait(struct i915_request *to,
if (__emit_semaphore_wait(to, from, from->fence.seqno))
goto await_fence;
- to->sched.semaphores |= from->engine->mask;
+ to->sched.semaphores |= mask;
to->sched.flags |= I915_SCHED_HAS_SEMAPHORE_CHAIN;
return 0;
@@ -1338,7 +1340,7 @@ __i915_request_add_to_timeline(struct i915_request *rq)
i915_seqno_passed(prev->fence.seqno,
rq->fence.seqno));
- if (is_power_of_2(prev->engine->mask | rq->engine->mask))
+ if (is_power_of_2(READ_ONCE(prev->engine)->mask | rq->engine->mask))
i915_sw_fence_await_sw_fence(&rq->submit,
&prev->submit,
&rq->submitq);
--
2.20.1
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