Commit e2300560 authored by Chris Wilson's avatar Chris Wilson Committed by Joonas Lahtinen
Browse files

drm/i915/gt: Hold context/request reference while breadcrumbs are active 



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: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200801160225.6814-2-chris@chris-wilson.co.uk


Signed-off-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
[Joonas: Rebased and reordered into drm-intel-gt-next branch]
Signed-off-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
parent 3f7dc107

drivers/gpu/drm/i915/gt/intel_breadcrumbs.c

+70 −33
Original line number Diff line number Diff line
@@ -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"
@@ -99,6 +100,22 @@ 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);
@@ -107,6 +124,9 @@ 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))
@@ -158,10 +178,11 @@ static bool __signal_request(struct i915_request *rq, struct list_head *signals) 
{

	clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);



	if (!__dma_fence_signal(&rq->fence))

	if (!__dma_fence_signal(&rq->fence)) {

		i915_request_put(rq);

		return false;

	}



	i915_request_get(rq);

	list_add_tail(&rq->signal_link, signals);

	return true;

}
@@ -209,8 +230,8 @@ 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);

				add_retire(b, ce->timeline);

				remove_signaling_context(b, ce);

			}

		}

	}
@@ -279,6 +300,9 @@ void intel_breadcrumbs_park(struct intel_breadcrumbs *b) 
	spin_lock_irqsave(&b->irq_lock, flags);

	__intel_breadcrumbs_disarm_irq(b);

	spin_unlock_irqrestore(&b->irq_lock, flags);



	if (!list_empty(&b->signalers))

		irq_work_queue(&b->irq_work);

}



void intel_breadcrumbs_free(struct intel_breadcrumbs *b)
@@ -295,6 +319,8 @@ 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
@@ -306,8 +332,10 @@ static void insert_breadcrumb(struct i915_request *rq, 
		return;

	}



	__intel_breadcrumbs_arm_irq(b);



	if (list_empty(&ce->signals)) {

		add_signaling_context(b, ce);

		pos = &ce->signals;

	} else {

		/*

		 * We keep the seqno in retirement order, so we can break

		 * inside intel_engine_signal_breadcrumbs as soon as we've
@@ -329,9 +357,8 @@ static void insert_breadcrumb(struct i915_request *rq, 
			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);
@@ -412,23 +439,19 @@ 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);

}



void intel_engine_print_breadcrumbs(struct intel_engine_cs *engine,

				    struct drm_printer *p)

static void print_signals(struct intel_breadcrumbs *b, struct drm_printer *p)

{

	struct intel_breadcrumbs *b = engine->breadcrumbs;

	struct intel_context *ce;

	struct i915_request *rq;



	if (!b || list_empty(&b->signalers))

		return;



	drm_printf(p, "Signals:\n");



	spin_lock_irq(&b->irq_lock);
@@ -444,3 +467,17 @@ void intel_engine_print_breadcrumbs(struct intel_engine_cs *engine, 
	}

	spin_unlock_irq(&b->irq_lock);

}



void intel_engine_print_breadcrumbs(struct intel_engine_cs *engine,

				    struct drm_printer *p)

{

	struct intel_breadcrumbs *b;



	b = engine->breadcrumbs;

	if (!b)

		return;



	drm_printf(p, "IRQ: %s\n", enableddisabled(b->irq_armed));

	if (!list_empty(&b->signalers))

		print_signals(b, p);

}

drivers/gpu/drm/i915/i915_request.c

+4 −5
Original line number Diff line number Diff line
@@ -296,13 +296,12 @@ bool i915_request_retire(struct i915_request *rq) 
	 */

	remove_from_engine(rq);



	spin_lock_irq(&rq->lock);

	i915_request_mark_complete(rq);

	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);

	}



	if (i915_request_has_waitboost(rq)) {

		GEM_BUG_ON(!atomic_read(&rq->engine->gt->rps.num_waiters));

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