Re: [patch 05/15] Generic Mutex Subsystem, mutex-core.patch

* Oleg Nesterov <[email protected]> wrote:

> > +	spin_lock(&lock->wait_lock);
> > +	__add_waiter(lock, waiter, ti, task __IP__);
> > +	set_task_state(task, task_state);
> 
> I can't understand why __mutex_lock_common() does xchg() after adding 
> the waiter to the ->wait_list. We are holding ->wait_lock, we can't 
> race with __mutex_unlock_nonatomic() - it calls wake_up() and sets 
> ->count under this spinlock.

we must make sure that the drop has not been dropped meanwhile, on the 
way in, between the fastpath-unlock atomic op, and the xchg() here.

	Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

---

• Follow-Ups:
  • Re: [patch 05/15] Generic Mutex Subsystem, mutex-core.patch
    • From: Oleg Nesterov <[email protected]>

• References:
  • [patch 05/15] Generic Mutex Subsystem, mutex-core.patch
    • From: Ingo Molnar <[email protected]>
  • Re: [patch 05/15] Generic Mutex Subsystem, mutex-core.patch
    • From: Oleg Nesterov <[email protected]>

• Prev by Date: [patch 6/8] mutex subsystem, core
• Next by Date: Re: [patch 05/15] Generic Mutex Subsystem, mutex-core.patch
• Previous by thread: Re: [patch 05/15] Generic Mutex Subsystem, mutex-core.patch
• Next by thread: Re: [patch 05/15] Generic Mutex Subsystem, mutex-core.patch
• Index(es):
  • Date
  • Thread

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]