Using engine->irq_posted for execlists, we are not always serialised by the tasklet as we supposed. On the reset paths, the tasklet is disabled and ignored. Instead, we manipulate the engine->irq_posted directly to account for the reset, but if an interrupt fired before the reset and so wrote to engine->irq_posted, that write may not be flushed from the local CPU's cacheline until much later as the tasklet is already active and so does not generate a mb(). To correctly serialise the interrupt with reset, we need serialisation on the set_bit() itself.
And at last Mika can be happy. Signed-off-by: Chris Wilson <[email protected]> Cc: Mika Kuoppala <[email protected]> Cc: Michał Winiarski <[email protected]> CC: Michel Thierry <[email protected]> Cc: Jeff McGee <[email protected]> Cc: Tvrtko Ursulin <[email protected]> --- drivers/gpu/drm/i915/i915_irq.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index fa7310766217..27aee25429b7 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -1405,10 +1405,9 @@ gen8_cs_irq_handler(struct intel_engine_cs *engine, u32 iir) bool tasklet = false; if (iir & GT_CONTEXT_SWITCH_INTERRUPT) { - if (READ_ONCE(engine->execlists.active)) { - __set_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted); - tasklet = true; - } + if (READ_ONCE(engine->execlists.active)) + tasklet = !test_and_set_bit(ENGINE_IRQ_EXECLIST, + &engine->irq_posted); } if (iir & GT_RENDER_USER_INTERRUPT) { -- 2.16.2 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
