On Tue, 2012-05-15 at 19:31 +0200, Peter Zijlstra wrote: > On Tue, 2012-05-15 at 13:25 -0400, Steven Rostedt wrote: > > On Tue, 2012-05-15 at 11:42 -0400, Steven Rostedt wrote: > > > On Tue, 2012-05-15 at 17:06 +0200, Peter Zijlstra wrote: > > > > On Tue, 2012-05-15 at 10:03 -0400, Steven Rostedt wrote: > > > > > > > > > > where readers may nest (the same task may grab the same rwsem for > > > > > read multiple times), but only one task may hold the rwsem at any > > > > > given > > > > > time (for read or write). > > > > > > > > Humm, that sounds iffy, rwsem isn't a recursive read lock only rwlock_t > > > > is. > > > > > > In that case, current -rt is broken. As it has it being a recursive lock > > > (without my patch). > > Nah not broken, just pointless. A recursive lock that's not used > recursively is fine. Heh, sure :-) But as -rt keeps it recursive, I didn't want to change that. > > > > > Why wouldn't it be recursive. If two different tasks are allowed to grab > > a read lock at the same time, why can't the same task grab a read lock > > twice? As long as it releases it the same amount of times. > > > > Now you can't grab a read lock if you have the write lock. > > rwsem is fifo-fair, if a writer comes in between the second read > acquisition (even by the same task) would block and you'd be a deadlock > since the write won't succeed since you're still holding a reader. Yep agreed. And this patch didn't change that either. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
