From: Chris Wilson Date: Tue, 10 Mar 2020 14:24:03 +0000 (+0000) Subject: drm/i915: Mark up racy read of active rq->engine X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=326611ddff603ca863adfd797f9e75297ac02539;p=linux.git drm/i915: Mark up racy read of active rq->engine 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 Reviewed-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20200310142403.5953-1-chris@chris-wilson.co.uk --- diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c index 506738dede162..1b1cda2438d1c 100644 --- a/drivers/gpu/drm/i915/gt/intel_rps.c +++ b/drivers/gpu/drm/i915/gt/intel_rps.c @@ -773,7 +773,7 @@ void intel_rps_park(struct intel_rps *rps) void intel_rps_boost(struct i915_request *rq) { - struct intel_rps *rps = &rq->engine->gt->rps; + struct intel_rps *rps = &READ_ONCE(rq->engine)->gt->rps; unsigned long flags; if (i915_request_signaled(rq) || !READ_ONCE(rps->active)) diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index 74169671afb5a..c0df71d7d0ff1 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);