Messages in this thread |  | | | Date | Wed, 27 Jul 2011 08:43:40 -0700 | | From | Darren Hart <> | | Subject | Re: rt_mutex: restore wait_lock init in __rt_mutex_init |
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On 07/27/2011 07:34 AM, Maarten Lankhorst wrote: > 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().
Ah... I didn't notice the move. I saw the change to the line after which add _raw and passed the wait_lock and thought it was expected that that call did the init (which it doesn't).
>> 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.
Right, makes sense.
>> 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);
So obvious now in hindsight :)
>> 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.
I still don't understand how pulseaudio ever caused this.
> 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
Duh, sorry, wasn't thinking straight. The requeue_pi support went in a while ago - what is missing is PI aware condvars which complete requeue_pi support.
Thanks!
-- Darren Hart Intel Open Source Technology Center Yocto Project - Linux Kernel
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