On Fri, 19 Dec 2008, Steven Rostedt wrote:
> > + } while (cmpxchg(¤t->state, state, block_state) != state);
>
> Doesn't this break archs that do not have cmpxchg?
We can use xchg. The waiter is protected against the RUNNING_MUTEX
state change via the mutex->lock. It's just some overcautioness when I
started to fix this.
> There might be another way. We could just use your TASK_RUNNING_MUTEX or
> trick for both mutexes and spinlocks.
The mechanisms should be the same for everything now.
> > - if (mtx)
> > - set_current_state(TASK_RUNNING);
> > - else {
> > - state = xchg(¤t->state, saved_state);
> > - if (unlikely(state == TASK_RUNNING))
> > - current->state = TASK_RUNNING;
> > - }
> > + rt_restore_current_state(saved_state);
>
> This is a bug. A mutex always leaves in the TASK_RUNNING state.
Duh, yes. So this should be:
rt_restore_current_state(!mtx ? saved_state : TASK_RUNNING);
> What about having the locking spinlocks and mutexes be almost identical.
> Like the rwlocks are (rwlocks and rwsems share the same code). We can use
> the RT_MUTEX_RUNNING trick for both. The only difference is that a mutex
> will always leave in the TASK_RUNNING state.
Good point.
Thanks,
tglx
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