When applying the context-barrier, we only care about the current
engines, as the next set of engines will be naturally after the barrier.
So we can skip holding the ctx->engines_mutex while constructing the
request by taking a sneaky reference to the i915_gem_engines instead.
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
---
Annotate the unlikely loop inside the rcu read lock.
---
drivers/gpu/drm/i915/gem/i915_gem_context.c | 94 ++++++++++++++-------
1 file changed, 63 insertions(+), 31 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c
b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 50ecc0b2b235..7c3997296798 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -261,6 +261,34 @@ static void free_engines_rcu(struct rcu_head *rcu)
free_engines(engines);
}
+static int engines_notify(struct i915_sw_fence *fence,
+ enum i915_sw_fence_notify state)
+{
+ struct i915_gem_engines *engines =
+ container_of(fence, typeof(*engines), fence);
+
+ switch (state) {
+ case FENCE_COMPLETE:
+ if (!list_empty(&engines->link)) {
+ struct i915_gem_context *ctx = engines->ctx;
+ unsigned long flags;
+
+ spin_lock_irqsave(&ctx->stale.lock, flags);
+ list_del(&engines->link);
+ spin_unlock_irqrestore(&ctx->stale.lock, flags);
+ }
+ i915_gem_context_put(engines->ctx);
+ break;
+
+ case FENCE_FREE:
+ init_rcu_head(&engines->rcu);
+ call_rcu(&engines->rcu, free_engines_rcu);
+ break;
+ }
+
+ return NOTIFY_DONE;
+}
+
static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx)
{
const struct intel_gt *gt = &ctx->i915->gt;
@@ -272,6 +300,8 @@ static struct i915_gem_engines *default_engines(struct
i915_gem_context *ctx)
if (!e)
return ERR_PTR(-ENOMEM);
+ i915_sw_fence_init(&e->fence, engines_notify);
+
for_each_engine(engine, gt, id) {
struct intel_context *ce;
@@ -519,41 +549,12 @@ static void kill_context(struct i915_gem_context *ctx)
kill_stale_engines(ctx);
}
-static int engines_notify(struct i915_sw_fence *fence,
- enum i915_sw_fence_notify state)
-{
- struct i915_gem_engines *engines =
- container_of(fence, typeof(*engines), fence);
-
- switch (state) {
- case FENCE_COMPLETE:
- if (!list_empty(&engines->link)) {
- struct i915_gem_context *ctx = engines->ctx;
- unsigned long flags;
-
- spin_lock_irqsave(&ctx->stale.lock, flags);
- list_del(&engines->link);
- spin_unlock_irqrestore(&ctx->stale.lock, flags);
- }
- i915_gem_context_put(engines->ctx);
- break;
-
- case FENCE_FREE:
- init_rcu_head(&engines->rcu);
- call_rcu(&engines->rcu, free_engines_rcu);
- break;
- }
-
- return NOTIFY_DONE;
-}
-
static void engines_idle_release(struct i915_gem_context *ctx,
struct i915_gem_engines *engines)
{
struct i915_gem_engines_iter it;
struct intel_context *ce;
- i915_sw_fence_init(&engines->fence, engines_notify);
INIT_LIST_HEAD(&engines->link);
engines->ctx = i915_gem_context_get(ctx);
@@ -1079,6 +1080,30 @@ static void cb_retire(struct i915_active *base)
kfree(cb);
}
+static inline struct i915_gem_engines *
+__context_engines_await(const struct i915_gem_context *ctx)
+{
+ struct i915_gem_engines *engines;
+
+ rcu_read_lock();
+ do {
+ engines = rcu_dereference(ctx->engines);
+ if (!unlikely(engines))
+ break;
+
+ if (!unlikely(i915_sw_fence_await(&engines->fence)))
+ continue;
+
+ if (likely(engines == rcu_access_pointer(ctx->engines)))
+ break;
+
+ i915_sw_fence_complete(&engines->fence);
+ } while(1);
+ rcu_read_unlock();
+
+ return engines;
+}
+
I915_SELFTEST_DECLARE(static intel_engine_mask_t context_barrier_inject_fault);
static int context_barrier_task(struct i915_gem_context *ctx,
intel_engine_mask_t engines,
@@ -1089,6 +1114,7 @@ static int context_barrier_task(struct i915_gem_context
*ctx,
{
struct context_barrier_task *cb;
struct i915_gem_engines_iter it;
+ struct i915_gem_engines *e;
struct intel_context *ce;
int err = 0;
@@ -1105,7 +1131,13 @@ static int context_barrier_task(struct i915_gem_context
*ctx,
return err;
}
- for_each_gem_engine(ce, i915_gem_context_lock_engines(ctx), it) {
+ e = __context_engines_await(ctx);
+ if (!e) {
+ i915_active_release(&cb->base);
+ return -ENOENT;
+ }
+
+ for_each_gem_engine(ce, e, it) {
struct i915_request *rq;
if (I915_SELFTEST_ONLY(context_barrier_inject_fault &
@@ -1136,7 +1168,7 @@ static int context_barrier_task(struct i915_gem_context
*ctx,
if (err)
break;
}
- i915_gem_context_unlock_engines(ctx);
+ i915_sw_fence_complete(&e->fence);
cb->task = err ? NULL : task; /* caller needs to unwind instead */
cb->data = data;
--
2.20.1
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