On Wed, Aug 17, 2022 at 04:14:20PM +0000, Andri Yngvason wrote: > Hi Greg, > > mið., 17. ágú. 2022 kl. 11:59 skrifaði Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>: > > > > On Wed, Aug 17, 2022 at 11:32:48AM +0000, Andri Yngvason wrote: > > > This fixes a race with the release-timer by adding acquire/release > > > barrier semantics. > > > > What race? > > > > The race is between the release timer and processing of hid input. It > is quite certain that these atomic checks are broken as is because > they're lacking memory barriers and this patch does fix an actual > problem for me. Perhaps you should say that in this changelog then. > > I must admit that I don't know exactly where the execution reordering > occurs and I haven't checked the generated assembly code, but if you > look at e.g. mt_expired_timeout(), you'll see that there's nothing to > keep the compiler or CPU from hoisting the test_bit() call above the > test_and_set_bit() call. > > > > > > > I noticed that contacts were sometimes sticking, even with the "sticky > > > fingers" quirk enabled. This fixes that problem. > > > > > > Cc: stable@xxxxxxxxxxxxxxx > > > Signed-off-by: Andri Yngvason <andri@xxxxxxxxxxx> > > > --- > > > drivers/hid/hid-multitouch.c | 8 ++++---- > > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c > > > index 2e72922e36f5..91a4d3fc30e0 100644 > > > --- a/drivers/hid/hid-multitouch.c > > > +++ b/drivers/hid/hid-multitouch.c > > > @@ -1186,7 +1186,7 @@ static void mt_touch_report(struct hid_device *hid, > > > int contact_count = -1; > > > > > > /* sticky fingers release in progress, abort */ > > > - if (test_and_set_bit(MT_IO_FLAGS_RUNNING, &td->mt_io_flags)) > > > + if (test_and_set_bit_lock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags)) > > > > So this is now a lock? > > > > Why not just use a real lock instead? > > > > I don't know. This stuff was introduced in > 9609827458c37d7b2c37f2a9255631c603a5004c by Benjamin Tissoires. Then this needs a "Fixes:" tag? thanks, greg k-h
