On 05/08/2016 09:56 PM, Davidlohr Bueso wrote: > The field is obviously updated w.o the lock and needs a READ_ONCE > while waiting for lock holder(s) to go away, just like we do with > all other ->count accesses.
This isn't actually fixing a bug because it's passed through several full barriers which will force reloading from sem->count. I think the patch is ok if you want it just for consistency anyway, but please change $subject and changelog. Regards, Peter Hurley > Signed-off-by: Davidlohr Bueso <dbu...@suse.de> > --- > kernel/locking/rwsem-xadd.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c > index df4dcb883b50..7d62772600cf 100644 > --- a/kernel/locking/rwsem-xadd.c > +++ b/kernel/locking/rwsem-xadd.c > @@ -494,7 +494,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore > *sem, int state) > } > schedule(); > set_current_state(state); > - } while ((count = sem->count) & RWSEM_ACTIVE_MASK); > + } while ((count = READ_ONCE(sem->count)) & RWSEM_ACTIVE_MASK); > > raw_spin_lock_irq(&sem->wait_lock); > } >
