sync: add internal refcounting to fences
If a fence is released while a timeline that one of it's pts is on is being
signaled, it is possible for that fence to be deleted before it is signaled.
This patch adds a refcount for internal references such as signaled pt
processing.
Change-Id: Ie8605e6fd2ac026c207220a03d84e1c1078ec719
Signed-off-by: Erik Gilling <konkers@android.com>
Signed-off-by: Ajay Dudani <adudani@codeaurora.org>
diff --git a/drivers/base/sync.c b/drivers/base/sync.c
index 13b26d2..be808b0 100644
--- a/drivers/base/sync.c
+++ b/drivers/base/sync.c
@@ -30,6 +30,7 @@
static void sync_fence_signal_pt(struct sync_pt *pt);
static int _sync_pt_has_signaled(struct sync_pt *pt);
+static void sync_fence_free(struct kref *kref);
static LIST_HEAD(sync_timeline_list_head);
static DEFINE_SPINLOCK(sync_timeline_list_lock);
@@ -113,7 +114,7 @@
{
struct sync_timeline *obj = pt->parent;
unsigned long flags;
- bool needs_freeing;
+ bool needs_freeing = false;
spin_lock_irqsave(&obj->active_list_lock, flags);
if (!list_empty(&pt->active_list))
@@ -121,8 +122,11 @@
spin_unlock_irqrestore(&obj->active_list_lock, flags);
spin_lock_irqsave(&obj->child_list_lock, flags);
- list_del(&pt->child_list);
- needs_freeing = obj->destroyed && list_empty(&obj->child_list_head);
+ if (!list_empty(&pt->child_list)) {
+ list_del_init(&pt->child_list);
+ needs_freeing = obj->destroyed &&
+ list_empty(&obj->child_list_head);
+ }
spin_unlock_irqrestore(&obj->child_list_lock, flags);
if (needs_freeing)
@@ -141,18 +145,22 @@
struct sync_pt *pt =
container_of(pos, struct sync_pt, active_list);
- if (_sync_pt_has_signaled(pt))
- list_move(pos, &signaled_pts);
+ if (_sync_pt_has_signaled(pt)) {
+ list_del_init(pos);
+ list_add(&pt->signaled_list, &signaled_pts);
+ kref_get(&pt->fence->kref);
+ }
}
spin_unlock_irqrestore(&obj->active_list_lock, flags);
list_for_each_safe(pos, n, &signaled_pts) {
struct sync_pt *pt =
- container_of(pos, struct sync_pt, active_list);
+ container_of(pos, struct sync_pt, signaled_list);
list_del_init(pos);
sync_fence_signal_pt(pt);
+ kref_put(&pt->fence->kref, sync_fence_free);
}
}
EXPORT_SYMBOL(sync_timeline_signal);
@@ -253,6 +261,7 @@
if (fence->file == NULL)
goto err;
+ kref_init(&fence->kref);
strlcpy(fence->name, name, sizeof(fence->name));
INIT_LIST_HEAD(&fence->pt_list_head);
@@ -361,6 +370,16 @@
return 0;
}
+static void sync_fence_detach_pts(struct sync_fence *fence)
+{
+ struct list_head *pos, *n;
+
+ list_for_each_safe(pos, n, &fence->pt_list_head) {
+ struct sync_pt *pt = container_of(pos, struct sync_pt, pt_list);
+ sync_timeline_remove_pt(pt);
+ }
+}
+
static void sync_fence_free_pts(struct sync_fence *fence)
{
struct list_head *pos, *n;
@@ -564,18 +583,37 @@
}
EXPORT_SYMBOL(sync_fence_wait);
+static void sync_fence_free(struct kref *kref)
+{
+ struct sync_fence *fence = container_of(kref, struct sync_fence, kref);
+
+ sync_fence_free_pts(fence);
+
+ kfree(fence);
+}
+
static int sync_fence_release(struct inode *inode, struct file *file)
{
struct sync_fence *fence = file->private_data;
unsigned long flags;
+ /*
+ * We need to remove all ways to access this fence before droping
+ * our ref.
+ *
+ * start with its membership in the global fence list
+ */
spin_lock_irqsave(&sync_fence_list_lock, flags);
list_del(&fence->sync_fence_list);
spin_unlock_irqrestore(&sync_fence_list_lock, flags);
- sync_fence_free_pts(fence);
+ /*
+ * remove its pts from their parents so that sync_timeline_signal()
+ * can't reference the fence.
+ */
+ sync_fence_detach_pts(fence);
- kfree(fence);
+ kref_put(&fence->kref, sync_fence_free);
return 0;
}
diff --git a/include/linux/sync.h b/include/linux/sync.h
index 943f414..00c9bae 100644
--- a/include/linux/sync.h
+++ b/include/linux/sync.h
@@ -16,6 +16,7 @@
#include <linux/types.h>
#ifdef __KERNEL__
+#include <linux/kref.h>
#include <linux/ktime.h>
#include <linux/list.h>
#include <linux/spinlock.h>
@@ -109,6 +110,7 @@
* @parent: sync_timeline to which this sync_pt belongs
* @child_list: membership in sync_timeline.child_list_head
* @active_list: membership in sync_timeline.active_list_head
+ * @signaled_list: membership in temorary signaled_list on stack
* @fence: sync_fence to which the sync_pt belongs
* @pt_list: membership in sync_fence.pt_list_head
* @status: 1: signaled, 0:active, <0: error
@@ -120,6 +122,7 @@
struct list_head child_list;
struct list_head active_list;
+ struct list_head signaled_list;
struct sync_fence *fence;
struct list_head pt_list;
@@ -133,6 +136,7 @@
/**
* struct sync_fence - sync fence
* @file: file representing this fence
+ * @kref: referenace count on fence.
* @name: name of sync_fence. Useful for debugging
* @pt_list_head: list of sync_pts in ths fence. immutable once fence
* is created
@@ -145,6 +149,7 @@
*/
struct sync_fence {
struct file *file;
+ struct kref kref;
char name[32];
/* this list is immutable once the fence is created */