Messages in this thread | | | Date | Tue, 7 Mar 2017 18:57:26 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH -v5 12/14] futex,rt_mutex: Restructure rt_mutex_finish_proxy_lock() |
| |
On Tue, Mar 07, 2017 at 03:18:46PM +0100, Thomas Gleixner wrote: > On Sat, 4 Mar 2017, Peter Zijlstra wrote: > > +/** > > + * rt_mutex_cleanup_proxy_lock() - Cleanup failed lock acquisition > > + * @lock: the rt_mutex we were woken on > > + * @waiter: the pre-initialized rt_mutex_waiter > > + * > > + * Clean up the failed lock acquisition as per rt_mutex_wait_proxy_lock(). > > + * > > + * Returns: > > + * true - did the cleanup, we done. > > + * false - we acquired the lock after rt_mutex_wait_proxy_lock() returned, > > + * caller should disregards its return value. > > Hmm. How would that happen? Magic owner assignement to a non waiter? The > callsite only calls here in the failed case.
Ah, but until the remove_waiter() below, we _still_ are a waiter, and thus can get assigned ownership.
> > + * > > + * Special API call for PI-futex support > > + */ > > +bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock, > > + struct rt_mutex_waiter *waiter) > > +{ > > + bool cleanup = false; > > + > > + raw_spin_lock_irq(&lock->wait_lock); > > + /* > > + * If we acquired the lock, no cleanup required. > > + */ > > + if (rt_mutex_owner(lock) != current) { > > + remove_waiter(lock, waiter);
See, up till this point, we still a waiter and any unlock can see us being one.
> > + fixup_rt_mutex_waiters(lock); > > + cleanup = true; > > + } > > + raw_spin_unlock_irq(&lock->wait_lock); > > + > > + return cleanup; > > +}
| |