Quoting Dave Airlie (2017-12-19 11:30:12)
> From: Dave Airlie <airl...@redhat.com>
>
> The vk cts test:
> dEQP-VK.api.external.semaphore.opaque_fd.export_multiple_times_temporary
>
> triggers a lot of
> VFS: Close: file count is 0
>
> This patch fixes it, but I'm guessing it's racy and someone will
> smell rcu, but I just wanted to send out the proof of fixing it
> so I remember.
>
> Signed-off-by: Dave Airlie <airl...@redhat.com>
> ---
> drivers/gpu/drm/drm_syncobj.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
> index f776fc1cc543..ffa5bbd75852 100644
> --- a/drivers/gpu/drm/drm_syncobj.c
> +++ b/drivers/gpu/drm/drm_syncobj.c
> @@ -361,6 +361,7 @@ static int drm_syncobj_file_release(struct inode *inode,
> struct file *file)
> {
> struct drm_syncobj *syncobj = file->private_data;
>
> + syncobj->file = NULL;
Oh. That's scary as the opposite side assumes that the syncobj->file is
assigned for the lifetime of the syncobj - once allocated is never
unset.
If we stop trying to reuse the struct file and just allocated one for
each fd, the complications just vanish?
diff --cc include/drm/drm_syncobj.h
index 3980602472c0,ba54e0e58bbc..000000000000
--- a/include/drm/drm_syncobj.h
+++ b/include/drm/drm_syncobj.h
@@@ -56,10 -57,8 +56,6 @@@ struct drm_syncobj
* @lock: Protects &cb_list and write-locks &fence.
*/
spinlock_t lock;
- /**
- * @file: A file backing for this syncobj.
- */
- struct file *file;
-
- struct rcu_head rcu;
};
typedef void (*drm_syncobj_func_t)(struct drm_syncobj *syncobj,
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 131695915acd..0cca2e792719 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -399,23 +399,6 @@ static const struct file_operations drm_syncobj_file_fops
= {
.release = drm_syncobj_file_release,
};
-static int drm_syncobj_alloc_file(struct drm_syncobj *syncobj)
-{
- struct file *file = anon_inode_getfile("syncobj_file",
- &drm_syncobj_file_fops,
- syncobj, 0);
- if (IS_ERR(file))
- return PTR_ERR(file);
-
- drm_syncobj_get(syncobj);
- if (cmpxchg(&syncobj->file, NULL, file)) {
- /* lost the race */
- fput(file);
- }
-
- return 0;
-}
-
/**
* drm_syncobj_get_fd - get a file descriptor from a syncobj
* @syncobj: Sync object to export
@@ -427,21 +410,24 @@ static int drm_syncobj_alloc_file(struct drm_syncobj
*syncobj)
*/
int drm_syncobj_get_fd(struct drm_syncobj *syncobj, int *p_fd)
{
- int ret;
+ struct file *file;
int fd;
fd = get_unused_fd_flags(O_CLOEXEC);
if (fd < 0)
return fd;
- if (!syncobj->file) {
- ret = drm_syncobj_alloc_file(syncobj);
- if (ret) {
- put_unused_fd(fd);
- return ret;
- }
+ file = anon_inode_getfile("syncobj_file",
+ &drm_syncobj_file_fops,
+ syncobj, 0);
+ if (IS_ERR(file)) {
+ put_unused_fd(fd);
+ return PTR_ERR(file);
}
- fd_install(fd, syncobj->file);
+
+ drm_syncobj_get(syncobj);
+ fd_install(fd, file);
+
*p_fd = fd;
return 0;
}
@@ -461,31 +447,24 @@ static int drm_syncobj_handle_to_fd(struct drm_file
*file_private,
return ret;
}
-static struct drm_syncobj *drm_syncobj_fdget(int fd)
-{
- struct file *file = fget(fd);
-
- if (!file)
- return NULL;
- if (file->f_op != &drm_syncobj_file_fops)
- goto err;
-
- return file->private_data;
-err:
- fput(file);
- return NULL;
-};
-
static int drm_syncobj_fd_to_handle(struct drm_file *file_private,
int fd, u32 *handle)
{
- struct drm_syncobj *syncobj = drm_syncobj_fdget(fd);
+ struct drm_syncobj *syncobj;
+ struct file *file;
int ret;
- if (!syncobj)
+ file = fget(fd);
+ if (!file)
return -EINVAL;
+ if (file->f_op != &drm_syncobj_file_fops) {
+ fput(file);
+ return -EINVAL;
+ }
+
/* take a reference to put in the idr */
+ syncobj = file->private_data;
drm_syncobj_get(syncobj);
idr_preload(GFP_KERNEL);
@@ -494,12 +473,11 @@ static int drm_syncobj_fd_to_handle(struct drm_file
*file_private,
spin_unlock(&file_private->syncobj_table_lock);
idr_preload_end();
- if (ret < 0) {
- fput(syncobj->file);
- return ret;
- }
- *handle = ret;
- return 0;
+ if (ret > 0)
+ *handle = ret;
+
+ fput(file);
+ return ret;
}
static int drm_syncobj_import_sync_file_fence(struct drm_file *file_private,
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