On Wed, Jan 29, 2020 at 10:15:45AM -0800, Davidlohr Bueso wrote: > We can avoid the unnecessary barrier on non LL/SC architectures, > such as x86. Instead, use the smp_mb__after_atomic() call. > > Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx> Reviewed-by: Johan Hovold <johan@xxxxxxxxxx> > --- > drivers/usb/class/cdc-acm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c > index 62f4fb9b362f..0bc4b558f387 100644 > --- a/drivers/usb/class/cdc-acm.c > +++ b/drivers/usb/class/cdc-acm.c > @@ -842,7 +842,7 @@ static void acm_tty_unthrottle(struct tty_struct *tty) > clear_bit(ACM_THROTTLED, &acm->flags); > > /* Matches the smp_mb__after_atomic() in acm_read_bulk_callback(). */ > - smp_mb(); > + smp_mb__after_atomic(); > > acm_submit_read_urbs(acm, GFP_KERNEL); > } We have another barrier in USB serial which can also be relaxed this way. I'll post a patch shortly. Johan
