dma-buf/sync-file: Defer creation of sync_file->name
authorChris Wilson <chris@chris-wilson.co.uk>
Tue, 16 May 2017 11:10:42 +0000 (12:10 +0100)
committerGustavo Padovan <gustavo.padovan@collabora.com>
Wed, 24 May 2017 16:08:29 +0000 (13:08 -0300)
commit71ebc9a3795818eab52e81bbcbdfae130ee35d9e
tree471cdf0619cc75a44a992c0916beb498b3c894d9
parentc16f291dee8b7dc28d4bd0f395ccecf3f898cd21
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
drivers/dma-buf/sync_debug.c
drivers/dma-buf/sync_file.c
include/linux/sync_file.h