From: Erik Gilling konkers@android.com
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.
Cc: Maarten Lankhorst maarten.lankhorst@canonical.com Cc: Erik Gilling konkers@android.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Rob Clark robclark@gmail.com Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Greg KH gregkh@linuxfoundation.org Cc: dri-devel@lists.freedesktop.org Cc: Android Kernel Team kernel-team@android.com Signed-off-by: Erik Gilling konkers@android.com Signed-off-by: John Stultz john.stultz@linaro.org --- drivers/staging/android/sync.c | 54 ++++++++++++++++++++++++++++++++++------ drivers/staging/android/sync.h | 5 ++++ 2 files changed, 51 insertions(+), 8 deletions(-)
diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c index 6cb7c88..7d4e9aa 100644 --- a/drivers/staging/android/sync.c +++ b/drivers/staging/android/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 @@ static void sync_timeline_remove_pt(struct sync_pt *pt) { 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 @@ static void sync_timeline_remove_pt(struct sync_pt *pt) 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 @@ void sync_timeline_signal(struct sync_timeline *obj) 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 @@ static struct sync_fence *sync_fence_alloc(const char *name) if (fence->file == NULL) goto err;
+ kref_init(&fence->kref); strlcpy(fence->name, name, sizeof(fence->name));
INIT_LIST_HEAD(&fence->pt_list_head); @@ -362,6 +371,16 @@ static int sync_fence_merge_pts(struct sync_fence *dst, struct sync_fence *src) 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; @@ -565,18 +584,37 @@ int sync_fence_wait(struct sync_fence *fence, long timeout) } 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/drivers/staging/android/sync.h b/drivers/staging/android/sync.h index 943f414..00c9bae 100644 --- a/drivers/staging/android/sync.h +++ b/drivers/staging/android/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 @@ struct sync_timeline { * @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 sync_pt { 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_pt { /** * 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_pt { */ struct sync_fence { struct file *file; + struct kref kref; char name[32];
/* this list is immutable once the fence is created */