The intel_ring.head is updated as the requests are retired, but is
sampled at any time as we submit requests. Furthermore, it tracks
RING_HEAD which is inherently asynchronous.
[ 148.630314] BUG: KCSAN: data-race in execlists_dequeue [i915] / i915_request_retire [i915]
[ 148.630349]
[ 148.630374] write to 0xffff8881f4e28ddc of 4 bytes by task 90 on cpu 2:
[ 148.630752] i915_request_retire+0xed/0x770 [i915]
[ 148.631123] retire_requests+0x7a/0xd0 [i915]
[ 148.631491] engine_retire+0xa6/0xe0 [i915]
[ 148.631523] process_one_work+0x3af/0x640
[ 148.631552] worker_thread+0x80/0x670
[ 148.631581] kthread+0x19a/0x1e0
[ 148.631609] ret_from_fork+0x1f/0x30
[ 148.631629]
[ 148.631652] read to 0xffff8881f4e28ddc of 4 bytes by task 14288 on cpu 3:
[ 148.632019] execlists_dequeue+0x1300/0x1680 [i915]
[ 148.632384] __execlists_submission_tasklet+0x48/0x60 [i915]
[ 148.632770] execlists_submit_request+0x38e/0x3c0 [i915]
[ 148.633146] submit_notify+0x8f/0xc0 [i915]
[ 148.633512] __i915_sw_fence_complete+0x5d/0x3e0 [i915]
[ 148.633875] i915_sw_fence_complete+0x58/0x80 [i915]
[ 148.634238] i915_sw_fence_commit+0x16/0x20 [i915]
[ 148.634613] __i915_request_queue+0x60/0x70 [i915]
[ 148.634985] i915_gem_do_execbuffer+0x2de0/0x42b0 [i915]
[ 148.635366] i915_gem_execbuffer2_ioctl+0x2ab/0x580 [i915]
[ 148.635400] drm_ioctl_kernel+0xe9/0x130
[ 148.635429] drm_ioctl+0x27d/0x45e
[ 148.635456] ksys_ioctl+0x89/0xb0
[ 148.635482] __x64_sys_ioctl+0x42/0x60
[ 148.635510] do_syscall_64+0x6e/0x2c0
[ 148.635542] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 645.071436] BUG: KCSAN: data-race in gen8_emit_fini_breadcrumb [i915] / i915_request_retire [i915]
[ 645.071456]
[ 645.071467] write to 0xffff8881efe403dc of 4 bytes by task 14668 on cpu 3:
[ 645.071647] i915_request_retire+0xed/0x770 [i915]
[ 645.071824] i915_request_create+0x6c/0x160 [i915]
[ 645.072000] i915_gem_do_execbuffer+0x206d/0x42b0 [i915]
[ 645.072177] i915_gem_execbuffer2_ioctl+0x2ab/0x580 [i915]
[ 645.072194] drm_ioctl_kernel+0xe9/0x130
[ 645.072208] drm_ioctl+0x27d/0x45e
[ 645.072222] ksys_ioctl+0x89/0xb0
[ 645.072235] __x64_sys_ioctl+0x42/0x60
[ 645.072248] do_syscall_64+0x6e/0x2c0
[ 645.072263] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 645.072275]
[ 645.072285] read to 0xffff8881efe403dc of 4 bytes by interrupt on cpu 2:
[ 645.072458] gen8_emit_fini_breadcrumb+0x158/0x300 [i915]
[ 645.072636] __i915_request_submit+0x204/0x430 [i915]
[ 645.072809] execlists_dequeue+0x8e1/0x1680 [i915]
[ 645.072982] __execlists_submission_tasklet+0x48/0x60 [i915]
[ 645.073154] execlists_submit_request+0x38e/0x3c0 [i915]
[ 645.073330] submit_notify+0x8f/0xc0 [i915]
[ 645.073499] __i915_sw_fence_complete+0x5d/0x3e0 [i915]
[ 645.073668] i915_sw_fence_wake+0xc2/0x130 [i915]
[ 645.073836] __i915_sw_fence_complete+0x2cf/0x3e0 [i915]
[ 645.074006] i915_sw_fence_complete+0x58/0x80 [i915]
[ 645.074175] dma_i915_sw_fence_wake+0x3e/0x80 [i915]
[ 645.074344] signal_irq_work+0x62f/0x710 [i915]
[ 645.074360] irq_work_run_list+0xd7/0x110
[ 645.074373] irq_work_run+0x1d/0x50
[ 645.074386] smp_irq_work_interrupt+0x21/0x30
[ 645.074400] irq_work_interrupt+0xf/0x20
[ 645.074414] _raw_spin_unlock_irqrestore+0x34/0x40
[ 645.074585] execlists_submission_tasklet+0xde/0x170 [i915]
[ 645.074602] tasklet_action_common.isra.0+0x42/0x90
[ 645.074617] __do_softirq+0xc8/0x206
[ 645.074629] irq_exit+0xcd/0xe0
[ 645.074642] do_IRQ+0x44/0xc0
[ 645.074654] ret_from_intr+0x0/0x1c
[ 645.074667] finish_task_switch+0x73/0x230
[ 645.074679] __schedule+0x1c5/0x4c0
[ 645.074691] schedule+0x45/0xb0
[ 645.074704] worker_thread+0x194/0x670
[ 645.074716] kthread+0x19a/0x1e0
[ 645.074729] ret_from_fork+0x1f/0x30
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_ring.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_ring.h b/drivers/gpu/drm/i915/gt/intel_ring.h
index 5bdce24994aa..cc0ebca65167 100644
--- a/drivers/gpu/drm/i915/gt/intel_ring.h
+++ b/drivers/gpu/drm/i915/gt/intel_ring.h
@@ -88,6 +88,8 @@ static inline u32 intel_ring_offset(const struct i915_request *rq, void *addr)
static inline void
assert_ring_tail_valid(const struct intel_ring *ring, unsigned int tail)
{
+ unsigned int head = READ_ONCE(ring->head);
+
GEM_BUG_ON(!intel_ring_offset_valid(ring, tail));
/*
@@ -105,8 +107,7 @@ assert_ring_tail_valid(const struct intel_ring *ring, unsigned int tail)
* into the same cacheline as ring->head.
*/
#define cacheline(a) round_down(a, CACHELINE_BYTES)
- GEM_BUG_ON(cacheline(tail) == cacheline(ring->head) &&
- tail < ring->head);
+ GEM_BUG_ON(cacheline(tail) == cacheline(head) && tail < head);
#undef cacheline
}
--
2.20.1
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