On 20/07/2020 10:23, Chris Wilson wrote:
Currently we hold no actual reference to the request nor context while
they are attached to a breadcrumb. To avoid freeing the request/context
too early, we serialise with cancel-breadcrumbs by taking the irq
spinlock in i915_request_retire(). The alternative is to take a
reference for a new breadcrumb and release it upon signaling; removing
the more frequently hit contention point in i915_request_retire().
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 58 ++++++++++++++++-----
drivers/gpu/drm/i915/i915_request.c | 9 ++--
2 files changed, 48 insertions(+), 19 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
index d6008034869f..59e8cd505569 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
@@ -29,6 +29,7 @@
#include "i915_drv.h"
#include "i915_trace.h"
#include "intel_breadcrumbs.h"
+#include "intel_context.h"
#include "intel_gt_pm.h"
#include "intel_gt_requests.h"
@@ -100,6 +101,22 @@ static void __intel_breadcrumbs_disarm_irq(struct intel_breadcrumbs *b)
intel_gt_pm_put_async(b->irq_engine->gt);
}
+static void add_signaling_context(struct intel_breadcrumbs *b,
+ struct intel_context *ce)
+{
+ intel_context_get(ce);
+ list_add_tail(&ce->signal_link, &b->signalers);
+ if (list_is_first(&ce->signal_link, &b->signalers))
+ __intel_breadcrumbs_arm_irq(b);
+}
+
+static void remove_signaling_context(struct intel_breadcrumbs *b,
+ struct intel_context *ce)
+{
+ list_del(&ce->signal_link);
+ intel_context_put(ce);
+}
+
static inline bool __request_completed(const struct i915_request *rq)
{
return i915_seqno_passed(__hwsp_seqno(rq), rq->fence.seqno);
@@ -108,6 +125,9 @@ static inline bool __request_completed(const struct i915_request *rq)
__maybe_unused static bool
check_signal_order(struct intel_context *ce, struct i915_request *rq)
{
+ if (rq->context != ce)
+ return false;
+
if (!list_is_last(&rq->signal_link, &ce->signals) &&
i915_seqno_passed(rq->fence.seqno,
list_next_entry(rq, signal_link)->fence.seqno))
@@ -162,7 +182,6 @@ static bool __signal_request(struct i915_request *rq, struct list_head *signals)
if (!__dma_fence_signal(&rq->fence))
return false;
- i915_request_get(rq);
list_add_tail(&rq->signal_link, signals);
return true;
}
@@ -198,7 +217,8 @@ static void signal_irq_work(struct irq_work *work)
* spinlock as the callback chain may end up adding
* more signalers to the same context or engine.
*/
- __signal_request(rq, &signal);
+ if (!__signal_request(rq, &signal))
+ i915_request_put(rq);
Looks like __signal_request could do the request put but doesn't matter
hugely.
}
/*
@@ -210,7 +230,7 @@ static void signal_irq_work(struct irq_work *work)
/* Advance the list to the first incomplete request */
__list_del_many(&ce->signals, pos);
if (&ce->signals == pos) { /* now empty */
- list_del_init(&ce->signal_link);
+ remove_signaling_context(b, ce);
add_retire(b, ce->timeline);
}
}
@@ -282,6 +302,8 @@ void intel_breadcrumbs_park(struct intel_breadcrumbs *b)
spin_lock_irqsave(&b->irq_lock, flags);
if (b->irq_armed)
__intel_breadcrumbs_disarm_irq(b);
+ if (!list_empty(&b->signalers))
+ irq_work_queue(&b->irq_work);
spin_unlock_irqrestore(&b->irq_lock, flags);
}
@@ -299,6 +321,8 @@ static void insert_breadcrumb(struct i915_request *rq,
if (test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags))
return;
+ i915_request_get(rq);
+
/*
* If the request is already completed, we can transfer it
* straight onto a signaled list, and queue the irq worker for
@@ -307,11 +331,11 @@ static void insert_breadcrumb(struct i915_request *rq,
if (__request_completed(rq)) {
if (__signal_request(rq, &b->signaled_requests))
irq_work_queue(&b->irq_work);
+ else
+ i915_request_put(rq);
return;
}
- __intel_breadcrumbs_arm_irq(b);
-
/*
* We keep the seqno in retirement order, so we can break
* inside intel_engine_signal_breadcrumbs as soon as we've
@@ -326,16 +350,20 @@ static void insert_breadcrumb(struct i915_request *rq,
* start looking for our insertion point from the tail of
* the list.
*/
- list_for_each_prev(pos, &ce->signals) {
- struct i915_request *it =
- list_entry(pos, typeof(*it), signal_link);
-
- if (i915_seqno_passed(rq->fence.seqno, it->fence.seqno))
- break;
+ if (list_empty(&ce->signals)) {
+ add_signaling_context(b, ce);
+ GEM_BUG_ON(!b->irq_armed);
+ pos = &ce->signals;
+ } else {
+ list_for_each_prev(pos, &ce->signals) {
+ struct i915_request *it =
+ list_entry(pos, typeof(*it), signal_link);
+
+ if (i915_seqno_passed(rq->fence.seqno, it->fence.seqno))
+ break;
+ }
}
list_add(&rq->signal_link, pos);
- if (pos == &ce->signals) /* catch transitions from empty list */
- list_move_tail(&ce->signal_link, &b->signalers);
GEM_BUG_ON(!check_signal_order(ce, rq));
set_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
@@ -416,9 +444,10 @@ void i915_request_cancel_breadcrumb(struct i915_request *rq)
list_del(&rq->signal_link);
if (list_empty(&ce->signals))
- list_del_init(&ce->signal_link);
+ remove_signaling_context(b, ce);
clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
+ i915_request_put(rq);
}
spin_unlock(&b->irq_lock);
}
@@ -433,6 +462,7 @@ void intel_engine_print_breadcrumbs(struct intel_engine_cs *engine,
if (!b || list_empty(&b->signalers))
return;
+ drm_printf(p, "IRQ: %s\n", enableddisabled(b->irq_armed));
drm_printf(p, "Signals:\n");
spin_lock_irq(&b->irq_lock);
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 394587e70a2d..4ebb0f144ac4 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -300,12 +300,11 @@ bool i915_request_retire(struct i915_request *rq)
__i915_request_fill(rq, POISON_FREE);
rq->ring->head = rq->postfix;
- spin_lock_irq(&rq->lock);
- if (!i915_request_signaled(rq))
+ if (!i915_request_signaled(rq)) {
+ spin_lock_irq(&rq->lock);
dma_fence_signal_locked(&rq->fence);
- if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &rq->fence.flags))
- i915_request_cancel_breadcrumb(rq);
- spin_unlock_irq(&rq->lock);
+ spin_unlock_irq(&rq->lock);
+ }
if (i915_request_has_waitboost(rq)) {
GEM_BUG_ON(!atomic_read(&rq->engine->gt->rps.num_waiters));
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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