| Message ID | 20201217091524.10258-1-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915/gt: Drain the breadcrumbs just once | expand |
On Thu, Dec 17, 2020 at 09:15:24AM +0000, Chris Wilson wrote: > 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. > This was more or less exactly what I was going to suggest. Reviewed-by: Matthew Brost <matthew.brost@intel.com> > Reported-by: Matthew Brost <matthew.brost@intel.com> > Suggested-by: Matthew Brost <matthew.brost@intel.com> > Fixes: 9d5612ca165a ("drm/i915/gt: Defer enabling the breadcrumb interrupt to after submission") > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> > Cc: Matthew Brost <matthew.brost@intel.com> > --- > 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 >
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; }
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@intel.com> Suggested-by: Matthew Brost <matthew.brost@intel.com> Fixes: 9d5612ca165a ("drm/i915/gt: Defer enabling the breadcrumb interrupt to after submission") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Matthew Brost <matthew.brost@intel.com> --- 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(-)