fcntl spinlock in Linux?

[Volker Lendecke]

On Tue, Jan 29, 2013 at 04:37:03PM -0500, J. Bruce Fields wrote:
> It's probably also easiest to fix.

Including deadlock detection? I guess this would have to
look at all locks held by a thread, possibly on different
inodes.
 
> I'm not sure exactly what you mean here.  Waiters are on the fl_block
> list of the lock that they're waiting on, and on a global list (for
> deadlock detection).  They're not on the i_flock list.
> 
> Another possible problem is that waiters are all woken up on unlock or
> downgrade, when most of them may end up just blocking again immediately.

Sure, that is a problem. But if you give up complete
randomness you might run into fairness troubles. You have to
schedule by some means and this might determine certain
behaviour that apps would start to depend on.

Volker

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