If you want quick&dirty feedback read below, if you want something
smarter wait some more. :)
On 07/02/2020 11:11, Chris Wilson wrote:
If we have a set of active engines marked as being non-persistent, we
lose track of those if the user replaces those engines with
I915_CONTEXT_PARAM_ENGINES. As part of our uABI contract is that
non-persistent requests are terminated if they are no longer being
tracked by the user's context (in order to prevent a lost request
causing an untracked and so unstoppable GPU hang), we need to apply the
same context cancellation upon changing engines.
v2: Track stale engines[] so we only reap at context closure.
Fixes: a0e047156cde ("drm/i915/gem: Make context persistence optional")
Testcase: igt/gem_ctx_peristence/replace
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_context.c | 118 ++++++++++++++++--
.../gpu/drm/i915/gem/i915_gem_context_types.h | 13 +-
drivers/gpu/drm/i915/i915_sw_fence.c | 15 ++-
drivers/gpu/drm/i915/i915_sw_fence.h | 2 +-
4 files changed, 135 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 52a749691a8d..579215161c21 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -270,7 +270,8 @@ static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx)
if (!e)
return ERR_PTR(-ENOMEM);
- init_rcu_head(&e->rcu);
+ e->ctx = ctx;
+
for_each_engine(engine, gt, id) {
struct intel_context *ce;
@@ -450,7 +451,7 @@ static struct intel_engine_cs *active_engine(struct intel_context *ce)
return engine;
}
-static void kill_context(struct i915_gem_context *ctx)
+static void kill_engines(struct i915_gem_engines *engines)
{
struct i915_gem_engines_iter it;
struct intel_context *ce;
@@ -462,7 +463,7 @@ static void kill_context(struct i915_gem_context *ctx)
* However, we only care about pending requests, so only include
* engines on which there are incomplete requests.
*/
- for_each_gem_engine(ce, __context_engines_static(ctx), it) {
+ for_each_gem_engine(ce, engines, it) {
struct intel_engine_cs *engine;
if (intel_context_set_banned(ce))
@@ -484,10 +485,41 @@ static void kill_context(struct i915_gem_context *ctx)
* the context from the GPU, we have to resort to a full
* reset. We hope the collateral damage is worth it.
*/
- __reset_context(ctx, engine);
+ __reset_context(engines->ctx, engine);
}
}
+static void kill_stale_engines(struct i915_gem_context *ctx)
+{
+ struct i915_gem_engines *pos, *next;
+ unsigned long flags;
+
+ spin_lock_irqsave(&ctx->stale.lock, flags);
+ list_for_each_entry_safe(pos, next, &ctx->stale.engines, link) {
+ if (!i915_sw_fence_await(&pos->fence))
+ continue;
When is this path hit?
+
+ spin_unlock_irqrestore(&ctx->stale.lock, flags);
+
+ kill_engines(pos);
+
+ spin_lock_irqsave(&ctx->stale.lock, flags);
+ list_safe_reset_next(pos, next, link);
+ list_del_init(&pos->link);
+
+ i915_sw_fence_complete(&pos->fence);
This will trigger FENCE_FREE below?
+ }
+ spin_unlock_irqrestore(&ctx->stale.lock, flags);
+}
+
+static void kill_context(struct i915_gem_context *ctx)
+{
+ if (!list_empty(&ctx->stale.engines))
+ kill_stale_engines(ctx);
+
+ kill_engines(__context_engines_static(ctx));
+}
+
static void set_closed_name(struct i915_gem_context *ctx)
{
char *s;
@@ -602,6 +634,9 @@ __create_context(struct drm_i915_private *i915)
ctx->sched.priority = I915_USER_PRIORITY(I915_PRIORITY_NORMAL);
mutex_init(&ctx->mutex);
+ spin_lock_init(&ctx->stale.lock);
+ INIT_LIST_HEAD(&ctx->stale.engines);
+
mutex_init(&ctx->engines_mutex);
e = default_engines(ctx);
if (IS_ERR(e)) {
@@ -1529,6 +1564,71 @@ static const i915_user_extension_fn set_engines__extensions[] = {
[I915_CONTEXT_ENGINES_EXT_BOND] = set_engines__bond,
};
+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)) {
Why it is safe to look at the state of engines->link outside the lock?
We can have a race between context close and completion event on a stale
engine, right?
+ 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);
+ }
+ 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_engines *engines)
+{
+ struct i915_gem_engines_iter it;
+ struct intel_context *ce;
+ unsigned long flags;
+
+ GEM_BUG_ON(!engines);
+ i915_sw_fence_init(&engines->fence, engines_notify);
+
+ spin_lock_irqsave(&engines->ctx->stale.lock, flags);
+ list_add(&engines->link, &engines->ctx->stale.engines);
+ spin_unlock_irqrestore(&engines->ctx->stale.lock, flags);
+
+ for_each_gem_engine(ce, engines, it) {
+ struct dma_fence *fence;
+ int err;
+
+ if (!ce->timeline)
+ continue;
When does this happen?
+
+ fence = i915_active_fence_get(&ce->timeline->last_request);
+ if (!fence)
+ continue;
+
+ err = i915_sw_fence_await_dma_fence(&engines->fence,
+ fence, 0,
+ GFP_KERNEL);
+
+ dma_fence_put(fence);
+ if (err < 0) {
+ kill_engines(engines);
+ break;
Okay to leave already setup awaits active in this case?
+ }
+ }
+
+ i915_sw_fence_commit(&engines->fence);
+}
+
static int
set_engines(struct i915_gem_context *ctx,
const struct drm_i915_gem_context_param *args)
@@ -1571,7 +1671,8 @@ set_engines(struct i915_gem_context *ctx,
if (!set.engines)
return -ENOMEM;
- init_rcu_head(&set.engines->rcu);
+ set.engines->ctx = ctx;
+
for (n = 0; n < num_engines; n++) {
struct i915_engine_class_instance ci;
struct intel_engine_cs *engine;
@@ -1631,7 +1732,8 @@ set_engines(struct i915_gem_context *ctx,
set.engines = rcu_replace_pointer(ctx->engines, set.engines, 1);
mutex_unlock(&ctx->engines_mutex);
- call_rcu(&set.engines->rcu, free_engines_rcu);
+ /* Keep track of old engine sets for kill_context() */
+ engines_idle_release(set.engines);
return 0;
}
@@ -1646,7 +1748,6 @@ __copy_engines(struct i915_gem_engines *e)
if (!copy)
return ERR_PTR(-ENOMEM);
- init_rcu_head(©->rcu);
for (n = 0; n < e->num_engines; n++) {
if (e->engines[n])
copy->engines[n] = intel_context_get(e->engines[n]);
@@ -1890,7 +1991,8 @@ static int clone_engines(struct i915_gem_context *dst,
if (!clone)
goto err_unlock;
- init_rcu_head(&clone->rcu);
+ clone->ctx = dst;
+
for (n = 0; n < e->num_engines; n++) {
struct intel_engine_cs *engine;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
index 017ca803ab47..8d996dde8046 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
@@ -20,6 +20,7 @@
#include "gt/intel_context_types.h"
#include "i915_scheduler.h"
+#include "i915_sw_fence.h"
struct pid;
@@ -30,7 +31,12 @@ struct intel_timeline;
struct intel_ring;
struct i915_gem_engines {
- struct rcu_head rcu;
+ union {
+ struct rcu_head rcu;
+ struct list_head link;
+ };
+ struct i915_sw_fence fence;
+ struct i915_gem_context *ctx;
unsigned int num_engines;
struct intel_context *engines[];
};
@@ -173,6 +179,11 @@ struct i915_gem_context {
* context in messages.
*/
char name[TASK_COMM_LEN + 8];
+
+ struct {
+ struct spinlock lock;
+ struct list_head engines;
+ } stale;
};
#endif /* __I915_GEM_CONTEXT_TYPES_H__ */
diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c
index 51ba97daf2a0..9a20b7246f91 100644
--- a/drivers/gpu/drm/i915/i915_sw_fence.c
+++ b/drivers/gpu/drm/i915/i915_sw_fence.c
@@ -211,10 +211,19 @@ void i915_sw_fence_complete(struct i915_sw_fence *fence)
__i915_sw_fence_complete(fence, NULL);
}
-void i915_sw_fence_await(struct i915_sw_fence *fence)
+bool i915_sw_fence_await(struct i915_sw_fence *fence)
{
- debug_fence_assert(fence);
- WARN_ON(atomic_inc_return(&fence->pending) <= 1);
+ int old, new;
+
+ new = atomic_read(&fence->pending);
+ do {
+ if (new < 1)
+ return false;
+
+ old = new++;
+ } while ((new = atomic_cmpxchg(&fence->pending, old, new)) != old);
+
+ return true;
No idea what's happening here. Why was the existing code inadequate and
what are you changing?
Regards,
Tvrtko
}
void __i915_sw_fence_init(struct i915_sw_fence *fence,
diff --git a/drivers/gpu/drm/i915/i915_sw_fence.h b/drivers/gpu/drm/i915/i915_sw_fence.h
index 19e806ce43bc..30a863353ee6 100644
--- a/drivers/gpu/drm/i915/i915_sw_fence.h
+++ b/drivers/gpu/drm/i915/i915_sw_fence.h
@@ -91,7 +91,7 @@ int i915_sw_fence_await_reservation(struct i915_sw_fence *fence,
unsigned long timeout,
gfp_t gfp);
-void i915_sw_fence_await(struct i915_sw_fence *fence);
+bool i915_sw_fence_await(struct i915_sw_fence *fence);
void i915_sw_fence_complete(struct i915_sw_fence *fence);
static inline bool i915_sw_fence_signaled(const struct i915_sw_fence *fence)
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