On Wed, Oct 08, 2014 at 05:24:32PM -0700, Jason Gerecke wrote: > On Wed, Oct 8, 2014 at 2:40 PM, Dmitry Torokhov > <dmitry.torokhov@xxxxxxxxx> wrote: > > On Wed, Oct 08, 2014 at 11:25:42AM -0700, Jason Gerecke wrote: > >> Repeated connect/disconnect cycles under GNOME can trigger an occasional > >> OOPS from within e.g. wacom_led_select_store, presumably due to a timing > >> issue where userspace begins setting a value immediately before the > >> device disconnects and our shared data is whisked away. > >> > >> Signed-off-by: Jason Gerecke <killertofu@xxxxxxxxx> > >> --- > >> Changes in v2: > >> * Added in missing escape character > >> > >> drivers/hid/wacom_sys.c | 13 ++++++++++++- > >> 1 file changed, 12 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c > >> index 8593047..265429b 100644 > >> --- a/drivers/hid/wacom_sys.c > >> +++ b/drivers/hid/wacom_sys.c > >> @@ -641,6 +641,9 @@ static ssize_t wacom_led_select_store(struct device *dev, int set_id, > >> unsigned int id; > >> int err; > >> > >> + if (!wacom) > >> + return -ENODEV; > >> + > > > > Strong NAK. If device could disappear before this check it could as well > > disappear after your check. > > > > This patch does not solve anything. > > > > I assume I'll want to either disable interrupts or take a lock > depending on if `wacom_remove` is called from within the interrupt > context, but I haven't had to deal with concurrency in the kernel > before so I'm not entirely sure which option (or which primitive if > locking) would be appropriate... Actually the sysfs core should not allow anyone descend into sysfs show/store methods once you return from sysfs_remove*(). So you need to make sure that pointer is valid until then. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
