Matthew Brost pointed out that the while-loop on a shared breadcrumb was
inherently fraught with danger as it competed with the other users of
the breadcrumbs. However, in order to completely drain the re-arming irq
worker, the while-loop is a necessity, despite my optimism that we could
force cancellation with a couple of irq_work invocations.
Given that we can't merely drop the while-loop, use an activity counter on
the breadcrumbs to detect when we are parking the breadcrumbs for the
last time.
Based on a patch by Matthew Brost.
Reported-by: Matthew Brost <matthew.brost@xxxxxxxxx>
Suggested-by: Matthew Brost <matthew.brost@xxxxxxxxx>
Fixes: 9d5612ca165a ("drm/i915/gt: Defer enabling the breadcrumb interrupt to after submission")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 10 ++++++----
drivers/gpu/drm/i915/gt/intel_breadcrumbs.h | 13 ++++++++++++-
drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h | 6 ++++--
drivers/gpu/drm/i915/gt/intel_engine_pm.c | 1 +
4 files changed, 23 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
index 00918300f53f..3c62fd6daa76 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
@@ -332,17 +332,19 @@ void intel_breadcrumbs_reset(struct intel_breadcrumbs *b)
spin_unlock_irqrestore(&b->irq_lock, flags);
}
-void intel_breadcrumbs_park(struct intel_breadcrumbs *b)
+void __intel_breadcrumbs_park(struct intel_breadcrumbs *b)
{
- /* Kick the work once more to drain the signalers */
+ if (!READ_ONCE(b->irq_armed))
+ return;
+
+ /* Kick the work once more to drain the signalers, and disarm the irq */
irq_work_sync(&b->irq_work);
- while (unlikely(READ_ONCE(b->irq_armed))) {
+ while (READ_ONCE(b->irq_armed) && !atomic_read(&b->active)) {
local_irq_disable();
signal_irq_work(&b->irq_work);
local_irq_enable();
cond_resched();
}
- GEM_BUG_ON(!list_empty(&b->signalers));
}
void intel_breadcrumbs_free(struct intel_breadcrumbs *b)
diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.h b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.h
index ed3d1deabfbd..75cc9cff3ae3 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.h
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.h
@@ -19,7 +19,18 @@ intel_breadcrumbs_create(struct intel_engine_cs *irq_engine);
void intel_breadcrumbs_free(struct intel_breadcrumbs *b);
void intel_breadcrumbs_reset(struct intel_breadcrumbs *b);
-void intel_breadcrumbs_park(struct intel_breadcrumbs *b);
+void __intel_breadcrumbs_park(struct intel_breadcrumbs *b);
+
+static inline void intel_breadcrumbs_unpark(struct intel_breadcrumbs *b)
+{
+ atomic_inc(&b->active);
+}
+
+static inline void intel_breadcrumbs_park(struct intel_breadcrumbs *b)
+{
+ if (atomic_dec_and_test(&b->active))
+ __intel_breadcrumbs_park(b);
+}
static inline void
intel_engine_signal_breadcrumbs(struct intel_engine_cs *engine)
diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h b/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h
index a74bb3062bd8..d85a6f74fb87 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h
@@ -29,8 +29,7 @@
* the overhead of waking that client is much preferred.
*/
struct intel_breadcrumbs {
- /* Not all breadcrumbs are attached to physical HW */
- struct intel_engine_cs *irq_engine;
+ atomic_t active;
spinlock_t signalers_lock; /* protects the list of signalers */
struct list_head signalers;
@@ -40,6 +39,9 @@ struct intel_breadcrumbs {
struct irq_work irq_work; /* for use from inside irq_lock */
unsigned int irq_enabled;
bool irq_armed;
+
+ /* Not all breadcrumbs are attached to physical HW */
+ struct intel_engine_cs *irq_engine;
};
#endif /* __INTEL_BREADCRUMBS_TYPES__ */
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
index 499b09cb4acf..d74e748f677a 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
@@ -65,6 +65,7 @@ static int __engine_unpark(struct intel_wakeref *wf)
if (engine->unpark)
engine->unpark(engine);
+ intel_breadcrumbs_unpark(engine->breadcrumbs);
intel_engine_unpark_heartbeat(engine);
return 0;
}
--
2.20.1
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