On Wed, Mar 30, 2016 at 10:03:27PM +0200, Boris Brezillon wrote: > PWM devices are not protected against concurrent accesses. The lock in > pwm_device might let PWM users think it is, but it's actually only > protecting the enabled state. > > Removing this lock should be fine as long as all PWM users are aware that > accesses to the PWM device have to be serialized, which seems to be the > case for all of them except the sysfs interface. > Patch the sysfs code by adding a lock to the pwm_export struct and making > sure it's taken for all accesses to the exported PWM device. > > Signed-off-by: Boris Brezillon <boris.brezil...@free-electrons.com> > --- > drivers/pwm/core.c | 19 ++++-------------- > drivers/pwm/sysfs.c | 57 > ++++++++++++++++++++++++++++++++++++++++++----------- > include/linux/pwm.h | 2 -- > 3 files changed, 50 insertions(+), 28 deletions(-)
This is a little overzealous. Only accesses that can cause races need to be protected by the lock. All of the *_show() callbacks don't modify the PWM device in any way, so there is no need to protect them against concurrent accesses. I've dropped the changes when applying. Thanks, Thierry
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