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Affects 5.10-rt and all later releases, up to and including when rt was merged into mainline. This problem has been reported in two other linux-rt-users postings, [PREEMPT_RT] i915: fix PREEMPT_RT locking splats (Clark Williams) [linux-5.12.y-rt] drm/i915/gt: Fix a lockdep warning with interrupts enabled (Jun Miao) Neither of these submit the obvious solution, nor, AFAICT, has either yet been acted on. So I muddy the waters further by submitting this, a third fix. Signed-off-by: Joe Korty Tested-by: Joe Korty Index: b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c =================================================================== --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c @@ -34,6 +34,16 @@ #include "intel_gt_pm.h" #include "intel_gt_requests.h" +#include + +struct event_lock { + local_lock_t l; +}; + +static DEFINE_PER_CPU(struct event_lock, event_lock) = { + .l = INIT_LOCAL_LOCK(l), +}; + static bool irq_enable(struct intel_engine_cs *engine) { if (!engine->irq_enable) @@ -342,9 +352,9 @@ void intel_breadcrumbs_park(struct intel /* Kick the work once more to drain the signalers */ irq_work_sync(&b->irq_work); while (unlikely(READ_ONCE(b->irq_armed))) { - local_irq_disable(); + local_lock_irq(&event_lock.l); signal_irq_work(&b->irq_work); - local_irq_enable(); + local_unlock_irq(&event_lock.l); cond_resched(); } GEM_BUG_ON(!list_empty(&b->signalers));