On Tue, May 16, 2017 at 12:10:42PM +0100, Chris Wilson wrote:
Constructing the name takes the majority of the time for allocating a sync_file to wrap a fence, and the name is very rarely used (only via the sync_file status user interface). To reduce the impact on the common path (that of creating sync_file to pass around), defer the construction of the name until it is first used.
v2: Update kerneldoc (kbuild test robot) v3: sync_debug.c was peeking at the name v4: Comment upon the potential race between two users of sync_file_get_name() and claim that such a race is below the level of notice. However, to prevent any future nuisance, use a global spinlock to serialize the assignment of the name. v5: Completely avoid the read/write race by only storing the name passed in from the user inside sync_file->user_name and passing in a buffer to dynamically construct the name otherwise.
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Gustavo Padovan gustavo@padovan.org Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: David Herrmann dh.herrmann@gmail.com
drivers/dma-buf/sync_debug.c | 4 +++- drivers/dma-buf/sync_file.c | 39 ++++++++++++++++++++++++++++++++------- include/linux/sync_file.h | 5 +++-- 3 files changed, 38 insertions(+), 10 deletions(-)
diff --git a/drivers/dma-buf/sync_debug.c b/drivers/dma-buf/sync_debug.c index 4b1731ee7458..59a3b2f8ee91 100644 --- a/drivers/dma-buf/sync_debug.c +++ b/drivers/dma-buf/sync_debug.c @@ -132,9 +132,11 @@ static void sync_print_obj(struct seq_file *s, struct sync_timeline *obj) static void sync_print_sync_file(struct seq_file *s, struct sync_file *sync_file) {
- char buf[128]; int i;
- seq_printf(s, "[%p] %s: %s\n", sync_file, sync_file->name,
seq_printf(s, "[%p] %s: %s\n", sync_file,
sync_file_get_name(sync_file, buf, sizeof(buf)),sync_status_str(dma_fence_get_status(sync_file->fence)));
if (dma_fence_is_array(sync_file->fence)) {
diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c index c9eb4997cfcc..d7e219d2669d 100644 --- a/drivers/dma-buf/sync_file.c +++ b/drivers/dma-buf/sync_file.c @@ -80,11 +80,6 @@ struct sync_file *sync_file_create(struct dma_fence *fence)
sync_file->fence = dma_fence_get(fence);
- snprintf(sync_file->name, sizeof(sync_file->name), "%s-%s%llu-%d",
fence->ops->get_driver_name(fence),fence->ops->get_timeline_name(fence), fence->context,fence->seqno);- return sync_file;
} EXPORT_SYMBOL(sync_file_create); @@ -129,6 +124,36 @@ struct dma_fence *sync_file_get_fence(int fd) } EXPORT_SYMBOL(sync_file_get_fence);
+/**
- sync_file_get_name - get the name of the sync_file
- @sync_file: sync_file to get the fence from
- @buf: destination buffer to copy sync_file name into
- @len: available size of destination buffer.
- Each sync_file may have a name assigned either by the user (when merging
- sync_files together) or created from the fence it contains. In the latter
- case construction of the name is deferred until use, and so requires
- sync_file_get_name().
- Returns: a string representing the name.
- */
+char *sync_file_get_name(struct sync_file *sync_file, char *buf, int len) +{
- if (sync_file->user_name[0]) {
strlcpy(buf, sync_file->user_name, len);- } else {
struct dma_fence *fence = sync_file->fence;snprintf(buf, len, "%s-%s%llu-%d",fence->ops->get_driver_name(fence),fence->ops->get_timeline_name(fence),fence->context,fence->seqno);- }
- return buf;
+}
static int sync_file_set_fence(struct sync_file *sync_file, struct dma_fence **fences, int num_fences) { @@ -266,7 +291,7 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a, goto err; }
- strlcpy(sync_file->name, name, sizeof(sync_file->name));
- strlcpy(sync_file->user_name, name, sizeof(sync_file->user_name)); return sync_file;
err: @@ -419,7 +444,7 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file, }
no_fences:
- strlcpy(info.name, sync_file->name, sizeof(info.name));
- sync_file_get_name(sync_file, info.name, sizeof(info.name)); info.status = dma_fence_is_signaled(sync_file->fence); info.num_fences = num_fences;
diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h index d37beefdfbd5..5226d62ae91b 100644 --- a/include/linux/sync_file.h +++ b/include/linux/sync_file.h @@ -23,7 +23,7 @@ /**
- struct sync_file - sync file to export to the userspace
- @file: file representing this fence
- @name: name of sync_file. Useful for debugging
- @user_name: name of sync_file. Useful for debugging
- @sync_file_list: membership in global file list
- @wq: wait queue for fence signaling
- @fence: fence with the fences in the sync_file
@@ -31,7 +31,7 @@ */ struct sync_file { struct file *file;
- char name[32];
Maybe inline kerneldoc an explain a bit better what's going on:
/** * @user_name: * * Name of the sync file provided by userspace, for merged fences. * Otherwise generated through driver callbacks (in which case the * entire array is 0). */
Might be overkill, so not going to insist at all. Either way:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Pls poke Gustavo or Sumits to also check it and pick it up.
Thanks, Daniel
- char user_name[32];
#ifdef CONFIG_DEBUG_FS struct list_head sync_file_list; #endif @@ -46,5 +46,6 @@ struct sync_file {
struct sync_file *sync_file_create(struct dma_fence *fence); struct dma_fence *sync_file_get_fence(int fd); +char *sync_file_get_name(struct sync_file *sync_file, char *buf, int len);
#endif /* _LINUX_SYNC_H */
2.11.0