From: Dave Airlie <airlied@xxxxxxxxxx>
This isn't needed currently, but to reuse sync file for Vulkan
permanent shared semaphore semantics, we need to be able to swap
the fence backing a sync file. This patch adds a mutex to the
sync file and uses to protect accesses to the fence and cb members.
v1.1: fix the locking (Julia Lawall).
v2: use rcu try one
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
---
drivers/dma-buf/sync_file.c | 82 +++++++++++++++++++++++++++++++++++----------
include/linux/sync_file.h | 5 ++-
2 files changed, 69 insertions(+), 18 deletions(-)
diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index 2321035..8b34f21 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -28,6 +28,10 @@
static const struct file_operations sync_file_fops;
+#define sync_file_held(obj) lockdep_is_held(&(obj)->lock)
+#define sync_file_assert_held(obj) \
+ lockdep_assert_held(&(obj)->lock)
+
static struct sync_file *sync_file_alloc(void)
{
struct sync_file *sync_file;
@@ -47,6 +51,9 @@ static struct sync_file *sync_file_alloc(void)
INIT_LIST_HEAD(&sync_file->cb.node);
+ RCU_INIT_POINTER(sync_file->fence, NULL);
+
+ mutex_init(&sync_file->lock);
return sync_file;
err:
@@ -80,7 +87,9 @@ struct sync_file *sync_file_create(struct dma_fence *fence)
if (!sync_file)
return NULL;
- sync_file->fence = dma_fence_get(fence);
+ dma_fence_get(fence);
+
+ RCU_INIT_POINTER(sync_file->fence, fence);
snprintf(sync_file->name, sizeof(sync_file->name), "%s-%s%llu-%d",
fence->ops->get_driver_name(fence),
@@ -124,13 +133,26 @@ struct dma_fence *sync_file_get_fence(int fd)
if (!sync_file)
return NULL;
- fence = dma_fence_get(sync_file->fence);
+ if (!rcu_access_pointer(sync_file->fence))
+ return NULL;
+
+ rcu_read_lock();
+ fence = dma_fence_get_rcu_safe(&sync_file->fence);
+ rcu_read_unlock();
+
fput(sync_file->file);
return fence;
}
EXPORT_SYMBOL(sync_file_get_fence);
+static inline struct dma_fence *
+sync_file_get_fence_locked(struct sync_file *sync_file)
+{
+ return rcu_dereference_protected(sync_file->fence,
+ sync_file_held(sync_file));
+}
+
static int sync_file_set_fence(struct sync_file *sync_file,
struct dma_fence **fences, int num_fences)
{
@@ -143,7 +165,7 @@ static int sync_file_set_fence(struct sync_file *sync_file,
* we own the reference of the dma_fence_array creation.
*/
if (num_fences == 1) {
- sync_file->fence = fences[0];
+ RCU_INIT_POINTER(sync_file->fence, fences[0]);
kfree(fences);
} else {
array = dma_fence_array_create(num_fences, fences,
@@ -152,17 +174,20 @@ static int sync_file_set_fence(struct sync_file *sync_file,
if (!array)
return -ENOMEM;
- sync_file->fence = &array->base;
+ RCU_INIT_POINTER(sync_file->fence, &array->base);
}
return 0;
}
+/* must be called with sync_file lock taken */
static struct dma_fence **get_fences(struct sync_file *sync_file,
int *num_fences)
{
- if (dma_fence_is_array(sync_file->fence)) {
- struct dma_fence_array *array = to_dma_fence_array(sync_file->fence);
+ struct dma_fence *fence = sync_file_get_fence_locked(sync_file);
+
+ if (dma_fence_is_array(fence)) {
+ struct dma_fence_array *array = to_dma_fence_array(fence);
*num_fences = array->num_fences;
return array->fences;
@@ -204,10 +229,13 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
if (!sync_file)
return NULL;
+ mutex_lock(&a->lock);
+ mutex_lock(&b->lock);
a_fences = get_fences(a, &a_num_fences);
b_fences = get_fences(b, &b_num_fences);
- if (a_num_fences > INT_MAX - b_num_fences)
- return NULL;
+ if (a_num_fences > INT_MAX - b_num_fences) {
+ goto unlock;
+ }
num_fences = a_num_fences + b_num_fences;
@@ -268,11 +296,17 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
goto err;
}
+ mutex_unlock(&b->lock);
+ mutex_unlock(&a->lock);
+
strlcpy(sync_file->name, name, sizeof(sync_file->name));
return sync_file;
err:
fput(sync_file->file);
+unlock:
+ mutex_unlock(&b->lock);
+ mutex_unlock(&a->lock);
return NULL;
}
@@ -281,10 +315,15 @@ static void sync_file_free(struct kref *kref)
{
struct sync_file *sync_file = container_of(kref, struct sync_file,
kref);
+ struct dma_fence *fence;
+
+ fence = rcu_dereference_protected(sync_file->fence, 1);
+ if (fence) {
+ if (test_bit(POLL_ENABLED, &fence->flags))
+ dma_fence_remove_callback(fence, &sync_file->cb);
+ dma_fence_put(fence);
+ }
- if (test_bit(POLL_ENABLED, &sync_file->fence->flags))
- dma_fence_remove_callback(sync_file->fence, &sync_file->cb);
- dma_fence_put(sync_file->fence);
kfree(sync_file);
}
@@ -299,16 +338,20 @@ static int sync_file_release(struct inode *inode, struct file *file)
static unsigned int sync_file_poll(struct file *file, poll_table *wait)
{
struct sync_file *sync_file = file->private_data;
+ unsigned int ret_val;
poll_wait(file, &sync_file->wq, wait);
+ mutex_lock(&sync_file->lock);
if (!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) {
if (dma_fence_add_callback(sync_file->fence, &sync_file->cb,
fence_check_cb_func) < 0)
wake_up_all(&sync_file->wq);
}
+ ret_val = dma_fence_is_signaled(sync_file->fence) ? POLLIN : 0;
+ mutex_unlock(&sync_file->lock);
- return dma_fence_is_signaled(sync_file->fence) ? POLLIN : 0;
+ return ret_val;
}
static long sync_file_ioctl_merge(struct sync_file *sync_file,
@@ -393,6 +436,7 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
if (info.flags || info.pad)
return -EINVAL;
+ mutex_lock(&sync_file->lock);
fences = get_fences(sync_file, &num_fences);
/*
@@ -404,13 +448,17 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
if (!info.num_fences)
goto no_fences;
- if (info.num_fences < num_fences)
- return -EINVAL;
+ if (info.num_fences < num_fences) {
+ ret = -EINVAL;
+ goto out;
+ }
size = num_fences * sizeof(*fence_info);
fence_info = kzalloc(size, GFP_KERNEL);
- if (!fence_info)
- return -ENOMEM;
+ if (!fence_info) {
+ ret = -ENOMEM;
+ goto out;
+ }
for (i = 0; i < num_fences; i++)
sync_fill_fence_info(fences[i], &fence_info[i]);
@@ -433,7 +481,7 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
out:
kfree(fence_info);
-
+ mutex_unlock(&sync_file->lock);
return ret;
}
diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h
index 3e3ab84..006412f 100644
--- a/include/linux/sync_file.h
+++ b/include/linux/sync_file.h
@@ -30,6 +30,7 @@
* @wq: wait queue for fence signaling
* @fence: fence with the fences in the sync_file
* @cb: fence callback information
+ * @lock: mutex to protect fence/cb - used for semaphores
*/
struct sync_file {
struct file *file;
@@ -41,8 +42,10 @@ struct sync_file {
wait_queue_head_t wq;
- struct dma_fence *fence;
+ struct dma_fence __rcu *fence;
struct dma_fence_cb cb;
+ /* protects the fence pointer and cb */
+ struct mutex lock;
};
#define POLL_ENABLED DMA_FENCE_FLAG_USER_BITS
--
2.7.4
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