[PATCH v2 08/14] drm/i915: Allow an request to be cancelled

Chris Wilson
2017-02-14T09:54:27Z

If we preempt a request and remove it from the execution queue, we need
to undo its global seqno and restart any waiters.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/intel_breadcrumbs.c | 71 +++++++++++++++++++++++++-------
drivers/gpu/drm/i915/intel_ringbuffer.h | 1 +
2 files changed, 57 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index 1445a8ff2e02..420bbaf1f1c0 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -333,22 +333,15 @@ static inline int wakeup_priority(struct intel_breadcrumbs *b,
return tsk->prio;
}

-void intel_engine_remove_wait(struct intel_engine_cs *engine,
- struct intel_wait *wait)
+static void __intel_engine_remove_wait(struct intel_engine_cs *engine,
+ struct intel_wait *wait)
{
struct intel_breadcrumbs *b = &engine->breadcrumbs;

- /* Quick check to see if this waiter was already decoupled from
- * the tree by the bottom-half to avoid contention on the spinlock
- * by the herd.
- */
- if (RB_EMPTY_NODE(&wait->node))
- return;
-
- spin_lock_irq(&b->lock);
+ assert_spin_locked(&b->lock);

if (RB_EMPTY_NODE(&wait->node))
- goto out_unlock;
+ goto out;

if (b->first_wait == wait) {
const int priority = wakeup_priority(b, wait->tsk);
@@ -414,11 +407,27 @@ void intel_engine_remove_wait(struct intel_engine_cs *engine,
GEM_BUG_ON(RB_EMPTY_NODE(&wait->node));
rb_erase(&wait->node, &b->waiters);

-out_unlock:
+out:
GEM_BUG_ON(b->first_wait == wait);
GEM_BUG_ON(rb_first(&b->waiters) !=
(b->first_wait ? &b->first_wait->node : NULL));
GEM_BUG_ON(!rcu_access_pointer(b->irq_seqno_bh) ^ RB_EMPTY_ROOT(&b->waiters));
+}
+
+void intel_engine_remove_wait(struct intel_engine_cs *engine,
+ struct intel_wait *wait)
+{
+ struct intel_breadcrumbs *b = &engine->breadcrumbs;
+
+ /* Quick check to see if this waiter was already decoupled from
+ * the tree by the bottom-half to avoid contention on the spinlock
+ * by the herd.
+ */
+ if (RB_EMPTY_NODE(&wait->node))
+ return;
+
+ spin_lock_irq(&b->lock);
+ __intel_engine_remove_wait(engine, wait);
spin_unlock_irq(&b->lock);
}

@@ -484,11 +493,13 @@ static int intel_breadcrumbs_signaler(void *arg)
dma_fence_signal(&request->fence);
local_bh_enable(); /* kick start the tasklets */

+ spin_lock_irq(&b->lock);
+
/* Wake up all other completed waiters and select the
* next bottom-half for the next user interrupt.
*/
- intel_engine_remove_wait(engine,
- &request->signaling.wait);
+ __intel_engine_remove_wait(engine,
+ &request->signaling.wait);

/* Find the next oldest signal. Note that as we have
* not been holding the lock, another client may
@@ -496,7 +507,6 @@ static int intel_breadcrumbs_signaler(void *arg)
* we just completed - so double check we are still
* the oldest before picking the next one.
*/
- spin_lock_irq(&b->lock);
if (request == rcu_access_pointer(b->first_signal)) {
struct rb_node *rb =
rb_next(&request->signaling.node);
@@ -504,6 +514,8 @@ static int intel_breadcrumbs_signaler(void *arg)
rb ? to_signaler(rb) : NULL);
}
rb_erase(&request->signaling.node, &b->signals);
+ RB_CLEAR_NODE(&request->signaling.node);
+
spin_unlock_irq(&b->lock);

i915_gem_request_put(request);
@@ -591,6 +603,35 @@ void intel_engine_enable_signaling(struct drm_i915_gem_request *request)
wake_up_process(b->signaler);
}

+void intel_engine_cancel_signaling(struct drm_i915_gem_request *request)
+{
+ struct intel_engine_cs *engine = request->engine;
+ struct intel_breadcrumbs *b = &engine->breadcrumbs;
+
+ assert_spin_locked(&request->lock);
+ GEM_BUG_ON(!request->signaling.wait.seqno);
+
+ spin_lock(&b->lock);
+
+ if (!RB_EMPTY_NODE(&request->signaling.node)) {
+ if (request == rcu_access_pointer(b->first_signal)) {
+ struct rb_node *rb =
+ rb_next(&request->signaling.node);
+ rcu_assign_pointer(b->first_signal,
+ rb ? to_signaler(rb) : NULL);
+ }
+ rb_erase(&request->signaling.node, &b->signals);
+ RB_CLEAR_NODE(&request->signaling.node);
+ }
+
+ __intel_engine_remove_wait(engine, &request->signaling.wait);
+
+ spin_unlock(&b->lock);
+
+ request->signaling.wait.seqno = 0;
+ i915_gem_request_put(request);
+}
+
int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine)
{
struct intel_breadcrumbs *b = &engine->breadcrumbs;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 63d4d203654c..dfb2ffe4f1d1 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -605,6 +605,7 @@ bool intel_engine_add_wait(struct intel_engine_cs *engine,
void intel_engine_remove_wait(struct intel_engine_cs *engine,
struct intel_wait *wait);
void intel_engine_enable_signaling(struct drm_i915_gem_request *request);
+void intel_engine_cancel_signaling(struct drm_i915_gem_request *request);

static inline bool intel_engine_has_waiter(const struct intel_engine_cs *engine)
{
--
2.11.0