Messages in this thread | | | Subject | Re: [PATCH] rtmutex: multiple candidate owners without unrelated boosting | From | Steven Rostedt <> | Date | Wed, 15 Dec 2010 09:02:46 -0500 |
| |
On Wed, 2010-12-15 at 09:02 +0100, Thomas Gleixner wrote: > On Tue, 14 Dec 2010, Steven Rostedt wrote: > > > On Tue, 2010-12-14 at 17:04 +0800, Lai Jiangshan wrote: > > > > OK, I was looking at this in a bit more detail (the coffee finally set > > in) and I was at first looking to nuke the cand_owner since it is > > redundant to cand_seq. But I think we can nuke the cand_seq instead and > > use the top_waiter as the decider. > > So you just use cand_owner (the name sucks) to flag that the waiter > has been woken up either by the boost code or by an unlock. The waiter > clears that flag with waiter->lock->wait_lock held before calling > schedule(). > > Though I think we do need it at all. wakeup of an already running task > is almost a nop, so having one less state to worry about is good.
I was hoping to remove it completely, and yes I was hoping we could because a wakeup of a woken task is almost a nop. But then I saw this in rt_mutex_adjust_prio_chain():
> /* > * Check the orig_waiter state. After we dropped the locks, > * the previous owner of the lock might have released the lock > - * and made us the pending owner: > + * and made us candidate owner: > */ > - if (orig_waiter && !orig_waiter->task) > + if (orig_waiter && orig_waiter->cand_owner) > goto out_unlock_pi; >
I'm not sure what else we could use to check if the original waiter has been given the lock.
-- Steve
| |