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linux-next/drivers/gpu
Chris Wilson cdd1cf799b drm: Make drm_read() more robust against multithreaded races
The current implementation of drm_read() faces a number of issues:

1. Upon an error, it consumes the event which may lead to the client
blocking.
2. Upon an error, it forgets about events already copied
3. If it fails to copy a single event with O_NONBLOCK it falls into a
infinite loop of reporting EAGAIN.
3. There is a race between multiple waiters and blocking reads of the
events list.

Here, we inline drm_dequeue_event() into drm_read() so that we can take
the spinlock around the list walking and event copying, and importantly
reorder the error handling to avoid the issues above.

Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Testcase: igt/drm_read
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2015-01-21 14:57:03 +01:00
..
drm drm: Make drm_read() more robust against multithreaded races 2015-01-21 14:57:03 +01:00
host1x gpu: host1x: mipi: Set MIPI_CAL_BIAS_PAD_CFG1 register 2014-11-13 16:11:57 +01:00
ipu-v3 gpu: ipu-di: Switch to DIV_ROUND_CLOSEST for DI clock divider calc 2015-01-07 19:15:04 +01:00
vga Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-10-13 16:23:15 +02:00
Makefile