From: Sebastian Andrzej Siewior <[email protected]> IRQ-Work (FIFO-1) will be preempted by the threaded-interrupt (FIFO-50) and the interrupt will poll on signaler_active while the irq-work can't make progress.
Solve this by adding a spinlock to prevent starvation and force completion. Signed-off-by: Maarten Lankhorst <[email protected]> --- drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 8 +++++++- drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h | 1 + 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c index c10ac0ab3bfa8..c2b174bfa1418 100644 --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c @@ -209,6 +209,7 @@ static void signal_irq_work(struct irq_work *work) intel_breadcrumbs_disarm_irq(b); rcu_read_lock(); + spin_lock(&b->signaler_active_sync); atomic_inc(&b->signaler_active); list_for_each_entry_rcu(ce, &b->signalers, signal_link) { struct i915_request *rq; @@ -246,6 +247,7 @@ static void signal_irq_work(struct irq_work *work) } } atomic_dec(&b->signaler_active); + spin_unlock(&b->signaler_active_sync); rcu_read_unlock(); llist_for_each_safe(signal, sn, signal) { @@ -290,6 +292,7 @@ intel_breadcrumbs_create(struct intel_engine_cs *irq_engine) init_llist_head(&b->signaled_requests); spin_lock_init(&b->irq_lock); + spin_lock_init(&b->signaler_active_sync); init_irq_work(&b->irq_work, signal_irq_work); b->irq_engine = irq_engine; @@ -487,8 +490,11 @@ void intel_context_remove_breadcrumbs(struct intel_context *ce, if (release) intel_context_put(ce); - while (atomic_read(&b->signaler_active)) + while (atomic_read(&b->signaler_active)) { + spin_lock(&b->signaler_active_sync); + spin_unlock(&b->signaler_active_sync); cpu_relax(); + } } static void print_signals(struct intel_breadcrumbs *b, struct drm_printer *p) diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h b/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h index bdf09fd67b6e7..28dae32628aab 100644 --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h @@ -40,6 +40,7 @@ struct intel_breadcrumbs { struct list_head signalers; struct llist_head signaled_requests; atomic_t signaler_active; + spinlock_t signaler_active_sync; spinlock_t irq_lock; /* protects the interrupt from hardirq context */ struct irq_work irq_work; /* for use from inside irq_lock */ -- 2.51.0
