lkml.org 
[lkml]   [2011]   [Jul]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: rt_mutex: restore wait_lock init in __rt_mutex_init
On 07/27/2011 11:37 AM, Thomas Gleixner wrote:
> On Wed, 27 Jul 2011, Darren Hart wrote:
>
>> Without the raw_spin_lock_init(), the wait_lock does not get properly
>> initialized with CONFIG_DEBUG_SPINLOCK. This can manifest in a BUG() in the
>> futex requeue_pi path when the pi_state->pi_mutex->wait_lock fails the magic
>> test in rt_mutex_start_proxy_lock()->raw_spin_lock(&lock->wait_lock).
> That's actively wrong. You reinitialize the lock for all other cases
> which call this via rt_mutex_init(). There is a reason why I moved the
> spin lock initializer out of __rt_mutex_init() into
> rt_mutex_init(). The lock name stuff for lockdep ends up to be
> "lock->wait_lock" for all rt_mutexes, which is pretty useless when you
> have to analyze a lockdep splat. Thanks for finding it nevertheless.
>
> So the correct fix is:
>
> Index: linux-2.6/kernel/rtmutex.c
> ===================================================================
> --- linux-2.6.orig/kernel/rtmutex.c
> +++ linux-2.6/kernel/rtmutex.c
> @@ -1296,7 +1296,7 @@ EXPORT_SYMBOL_GPL(__rt_mutex_init);
> void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
> struct task_struct *proxy_owner)
> {
> - __rt_mutex_init(lock, NULL);
> + rt_mutex_init(lock);
> debug_rt_mutex_proxy_lock(lock, proxy_owner);
> rt_mutex_set_owner(lock, proxy_owner);
> rt_mutex_deadlock_account_lock(lock, proxy_owner);
>
>
Seems to work. I no longer get a warning from pulseaudio either.
Also darren, at least on fedora 15 glibc supports requeue_pi.
support for that is in nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_*.S

Cheers,
Maarten


\
 
 \ /
  Last update: 2011-07-27 16:37    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site