dma-buf/sync-file: Defer creation of sync_file->name
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>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170516111042.24719-1-chris@chris-wilson.co.uk
diff --git a/drivers/dma-buf/sync_debug.c b/drivers/dma-buf/sync_debug.c
index a0d780a..82a6e7f 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)) {