Messages in this thread | | | Date | Wed, 14 Oct 2009 17:32:51 +0800 | From | Cong Wang <> | Subject | Re: [Patch v4] rwsem: fix rwsem_is_locked() bugs |
| |
Andrew Morton wrote: > On Thu, 8 Oct 2009 05:23:53 -0400 > Amerigo Wang <amwang@redhat.com> wrote: > >> --- a/include/linux/rwsem-spinlock.h >> +++ b/include/linux/rwsem-spinlock.h >> @@ -71,7 +71,13 @@ extern void __downgrade_write(struct rw_semaphore *sem); >> >> static inline int rwsem_is_locked(struct rw_semaphore *sem) >> { >> - return (sem->activity != 0); >> + int ret = 1; >> + >> + if (spin_trylock_irq(&sem->wait_lock)) { >> + ret = (sem->activity != 0); >> + spin_unlock_irq(&sem->wait_lock); >> + } >> + return ret; >> } > > a) probably to large to be inlined
Yeah, maybe, I forgot spin_trylock_irq() and spin_unlock_irq are macros.
> > b) the function will now cause bugs if called under > local_irq_disable(). That wasn't the case before. Fixable via > spin_lock_irqsave(). > > In the present kernel there don't appear to be any irqs-off callers. > There may of course be some out-of-tree ones which will get bitten by > this semantic change. > > If we decide to leave this new rule in place then we should add a > WARN_ON(irqs_disabled()) to prevent hitting people with a nasty, subtle > bug. > > Methinks that _irqsave() is better.
My bad, I misunderstood spin_lock_irqsave(), thus used spin_lock_irq(). :( Will update the patch now.
Thanks!
| |