[Intel-gfx] [PATCH 11/22] drm/i915/gem: Teach execbuf how to wait on future syncobj
Chris Wilson
chris at chris-wilson.co.uk
Wed May 20 07:54:52 UTC 2020
If a syncobj has not yet been assigned, treat it as a future fence and
install and wait upon a dma-fence-proxy. The proxy will be replace by
the real fence later, and that fence will be responsible for signaling
our waiter.
Link: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4854
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
.../gpu/drm/i915/gem/i915_gem_execbuffer.c | 21 ++-
drivers/gpu/drm/i915/i915_request.c | 153 ++++++++++++++++++
drivers/gpu/drm/i915/i915_scheduler.c | 41 +++++
drivers/gpu/drm/i915/i915_scheduler.h | 3 +
4 files changed, 216 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 219a36995b96..ce27da907dc3 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -5,6 +5,7 @@
*/
#include <linux/intel-iommu.h>
+#include <linux/dma-fence-proxy.h>
#include <linux/dma-resv.h>
#include <linux/sync_file.h>
#include <linux/uaccess.h>
@@ -2523,8 +2524,24 @@ await_fence_array(struct i915_execbuffer *eb,
continue;
fence = drm_syncobj_fence_get(syncobj);
- if (!fence)
- return -EINVAL;
+ if (!fence) {
+ struct dma_fence *old;
+
+ fence = dma_fence_create_proxy();
+ if (!fence)
+ return -ENOMEM;
+
+ spin_lock(&syncobj->lock);
+ old = rcu_dereference_protected(syncobj->fence, true);
+ if (unlikely(old)) {
+ dma_fence_put(fence);
+ fence = dma_fence_get(old);
+ } else {
+ rcu_assign_pointer(syncobj->fence,
+ dma_fence_get(fence));
+ }
+ spin_unlock(&syncobj->lock);
+ }
err = i915_request_await_dma_fence(eb->request, fence);
dma_fence_put(fence);
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 6f8b5794b73c..3f7d9e4bf89f 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -24,6 +24,7 @@
#include <linux/dma-fence-array.h>
#include <linux/dma-fence-chain.h>
+#include <linux/dma-fence-proxy.h>
#include <linux/irq_work.h>
#include <linux/prefetch.h>
#include <linux/sched.h>
@@ -398,6 +399,7 @@ static bool fatal_error(int error)
case 0: /* not an error! */
case -EAGAIN: /* innocent victim of a GT reset (__i915_request_reset) */
case -ETIMEDOUT: /* waiting for Godot (timer_i915_sw_fence_wake) */
+ case -EDEADLK: /* cyclic fence lockup (await_proxy) */
return false;
default:
return true;
@@ -1125,6 +1127,155 @@ i915_request_await_external(struct i915_request *rq, struct dma_fence *fence)
return err;
}
+struct await_proxy {
+ struct wait_queue_entry base;
+ struct i915_request *request;
+ struct dma_fence *fence;
+ struct timer_list timer;
+ struct work_struct work;
+ int (*attach)(struct await_proxy *ap);
+ void *data;
+};
+
+static void await_proxy_work(struct work_struct *work)
+{
+ struct await_proxy *ap = container_of(work, typeof(*ap), work);
+ struct i915_request *rq = ap->request;
+
+ del_timer_sync(&ap->timer);
+
+ if (ap->fence) {
+ int err = 0;
+
+ /*
+ * If the fence is external, we impose a 10s timeout.
+ * However, if the fence is internal, we skip a timeout in
+ * the belief that all fences are in-order (DAG, no cycles)
+ * and we can enforce forward progress by reset the GPU if
+ * necessary. A future fence, provided userspace, can trivially
+ * generate a cycle in the dependency graph, and so cause
+ * that entire cycle to become deadlocked and for no forward
+ * progress to either be made, and the driver being kept
+ * eternally awake.
+ */
+ if (dma_fence_is_i915(ap->fence) &&
+ !i915_sched_node_verify_dag(&rq->sched,
+ &to_request(ap->fence)->sched))
+ err = -EDEADLK;
+
+ if (!err) {
+ mutex_lock(&rq->context->timeline->mutex);
+ err = ap->attach(ap);
+ mutex_unlock(&rq->context->timeline->mutex);
+ }
+
+ /* Don't flag an error for co-dependent scheduling */
+ if (err == -EDEADLK) {
+ struct i915_sched_node *waiter =
+ &to_request(ap->fence)->sched;
+ struct i915_dependency *p;
+
+ list_for_each_entry_lockless(p,
+ &rq->sched.waiters_list,
+ wait_link) {
+ if (p->waiter == waiter &&
+ p->flags & I915_DEPENDENCY_WEAK) {
+ err = 0;
+ break;
+ }
+ }
+ }
+
+ if (err < 0)
+ i915_sw_fence_set_error_once(&rq->submit, err);
+ }
+
+ i915_sw_fence_complete(&rq->submit);
+
+ dma_fence_put(ap->fence);
+ kfree(ap);
+}
+
+static int
+await_proxy_wake(struct wait_queue_entry *entry,
+ unsigned int mode,
+ int flags,
+ void *fence)
+{
+ struct await_proxy *ap = container_of(entry, typeof(*ap), base);
+
+ ap->fence = dma_fence_get(fence);
+ schedule_work(&ap->work);
+
+ return 0;
+}
+
+static void
+await_proxy_timer(struct timer_list *t)
+{
+ struct await_proxy *ap = container_of(t, typeof(*ap), timer);
+
+ if (dma_fence_remove_proxy_listener(ap->base.private, &ap->base)) {
+ struct i915_request *rq = ap->request;
+
+ pr_notice("Asynchronous wait on unset proxy fence by %s:%s:%llx timed out\n",
+ rq->fence.ops->get_driver_name(&rq->fence),
+ rq->fence.ops->get_timeline_name(&rq->fence),
+ rq->fence.seqno);
+ i915_sw_fence_set_error_once(&rq->submit, -ETIMEDOUT);
+
+ schedule_work(&ap->work);
+ }
+}
+
+static int
+__i915_request_await_proxy(struct i915_request *rq,
+ struct dma_fence *fence,
+ unsigned long timeout,
+ int (*attach)(struct await_proxy *ap),
+ void *data)
+{
+ struct await_proxy *ap;
+
+ ap = kzalloc(sizeof(*ap), I915_FENCE_GFP);
+ if (!ap)
+ return -ENOMEM;
+
+ i915_sw_fence_await(&rq->submit);
+ mark_external(rq);
+
+ ap->base.private = fence;
+ ap->base.func = await_proxy_wake;
+ ap->request = rq;
+ INIT_WORK(&ap->work, await_proxy_work);
+ ap->attach = attach;
+ ap->data = data;
+
+ timer_setup(&ap->timer, await_proxy_timer, 0);
+ if (timeout)
+ mod_timer(&ap->timer, round_jiffies_up(jiffies + timeout));
+
+ dma_fence_add_proxy_listener(fence, &ap->base);
+ return 0;
+}
+
+static int await_proxy(struct await_proxy *ap)
+{
+ return i915_request_await_dma_fence(ap->request, ap->fence);
+}
+
+static int
+i915_request_await_proxy(struct i915_request *rq, struct dma_fence *fence)
+{
+ /*
+ * Wait until we know the real fence so that can optimise the
+ * inter-fence synchronisation.
+ */
+ return __i915_request_await_proxy(rq, fence,
+ i915_fence_timeout(rq->i915),
+ await_proxy, NULL);
+}
+
int
i915_request_await_dma_fence(struct i915_request *rq, struct dma_fence *fence)
{
@@ -1171,6 +1322,8 @@ i915_request_await_dma_fence(struct i915_request *rq, struct dma_fence *fence)
if (dma_fence_is_i915(fence))
ret = i915_request_await_request(rq, to_request(fence));
+ else if (dma_fence_is_proxy(fence))
+ ret = i915_request_await_proxy(rq, fence);
else
ret = i915_request_await_external(rq, fence);
if (ret < 0)
diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index cbb880b10c65..250832768279 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -469,6 +469,47 @@ int i915_sched_node_add_dependency(struct i915_sched_node *node,
return 0;
}
+bool i915_sched_node_verify_dag(struct i915_sched_node *waiter,
+ struct i915_sched_node *signaler)
+{
+ struct i915_dependency *dep, *p;
+ struct i915_dependency stack;
+ bool result = false;
+ LIST_HEAD(dfs);
+
+ if (list_empty(&waiter->waiters_list))
+ return true;
+
+ spin_lock_irq(&schedule_lock);
+
+ stack.signaler = signaler;
+ list_add(&stack.dfs_link, &dfs);
+
+ list_for_each_entry(dep, &dfs, dfs_link) {
+ struct i915_sched_node *node = dep->signaler;
+
+ if (node_signaled(node))
+ continue;
+
+ list_for_each_entry(p, &node->signalers_list, signal_link) {
+ if (p->signaler == waiter)
+ goto out;
+
+ if (list_empty(&p->dfs_link))
+ list_add_tail(&p->dfs_link, &dfs);
+ }
+ }
+
+ result = true;
+out:
+ list_for_each_entry_safe(dep, p, &dfs, dfs_link)
+ INIT_LIST_HEAD(&dep->dfs_link);
+
+ spin_unlock_irq(&schedule_lock);
+
+ return result;
+}
+
void i915_sched_node_fini(struct i915_sched_node *node)
{
struct i915_dependency *dep, *tmp;
diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
index 6f0bf00fc569..13432add8929 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.h
+++ b/drivers/gpu/drm/i915/i915_scheduler.h
@@ -28,6 +28,9 @@
void i915_sched_node_init(struct i915_sched_node *node);
void i915_sched_node_reinit(struct i915_sched_node *node);
+bool i915_sched_node_verify_dag(struct i915_sched_node *waiter,
+ struct i915_sched_node *signal);
+
bool __i915_sched_node_add_dependency(struct i915_sched_node *node,
struct i915_sched_node *signal,
struct i915_dependency *dep,
--
2.20.1
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