lkml.org 
[lkml]   [2009]   [Oct]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [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!


\
 
 \ /
  Last update: 2009-10-14 11:33    [W:0.995 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site