Messages in this thread | | | Date | Wed, 21 Dec 2005 16:57:42 +0100 | From | Ingo Molnar <> | Subject | Re: [patch 05/15] Generic Mutex Subsystem, mutex-core.patch |
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* Oleg Nesterov <oleg@tv-sign.ru> 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.
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