On Tue, Mar 12, 2019 at 10:54:33AM +0100, Uwe Kleine-König wrote: > On Tue, Mar 12, 2019 at 10:49:59AM +0100, Geert Uytterhoeven wrote: > > Hi Uwe, > > > > On Tue, Mar 12, 2019 at 10:23 AM Uwe Kleine-König > > <u.kleine-koenig@xxxxxxxxxxxxxx> wrote: > > > On Tue, Mar 12, 2019 at 12:16:34PM +0900, Yoshihiro Shimoda wrote: > > > > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c > > > > index 1581f6a..2fdd6611 100644 > > > > --- a/drivers/pwm/core.c > > > > +++ b/drivers/pwm/core.c > > > > > > @@ -368,10 +370,12 @@ int pwmchip_remove(struct pwm_chip *chip) > > > > > > > > free_pwms(chip); > > > > > > > > - pwmchip_sysfs_unexport(chip); > > > > - > > > > out: > > > > mutex_unlock(&pwm_lock); > > > > + > > > > + if (!ret) > > > > + pwmchip_sysfs_unexport(chip); > > > > + > > > > > > I wonder if this needs to be done before free_pwms is called. Otherwise > > > the pwmchip is already gone and then something is requested via sysfs. > > > > The chip itself is not freed, only the pwms array inside, which is not needed > > for matching in pwmchip_sysfs_unexport(), right? > > OK, then make this: > > I wonder if pwmchip_sysfs_unexport needs to be done before free_pwms is > called. Otherwise the PWMs's representation is already gone and then > something might be requested via sysfs. Agreed, I think sysfs needs to disappear before the chip does, otherwise we could have userspace racing with the kernel for access to sysfs while the PWM chip is already/only halfway gone. Thierry
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