On Mon, 2018-02-12 at 12:44 -0600, Benjamin Marzinski wrote: > On Sat, Feb 10, 2018 at 08:42:31PM +0100, Martin Wilck wrote: > > On Sat, 2018-02-10 at 17:11 +0100, Martin Wilck wrote: > > > On Fri, 2018-02-09 at 18:36 -0600, Benjamin Marzinski wrote: > > > > On Sat, Feb 10, 2018 at 12:36:05AM +0100, Martin Wilck wrote: > > > > > On Sat, 2018-02-10 at 00:28 +0100, Martin Wilck wrote: > > > > > > Maybe it's easier than we thought. Attached is a patch on > > > > > > top > > > > > > of > > > > > > yours that I think might work, please have a look. > > > > > > > > > > > > > > > > That one didn't even compile. This one is better. > > > > > > > > > > Martin > > > > > > > > How about this one instead. The idea is that once we are in the > > > > cleanup > > > > handler, we just cleanup and exit. But before we enter it, we > > > > atomically > > > > exchange running, and if running was 0, we pause(), since the > > > > checker > > > > is > > > > either about to cancel us, or already has. > > > > > > > > > > Yes, that should work. Nice. > > > > ... but I just realized that we don't rcu_register_thread() the TUR > > thread. Maybe we should if we use RCU primitives? > > Looking online, I see this. > > "void rcu_register_thread(void): For all RCU flavors other than > bullet-proof RCU, each thread must invoke this function before its > first > call to rcu_read_lock() or call_rcu(). If a given thread never > invokes > any RCU read-side functions, it need not invoke > rcu_register_thread(void)." > > That makes it sound like this is unnecessary for using the atomic > operations. Did you see something that makes you think differently? I > probably won't hurt to add it anyway. But, if it's fuzzy how to > correctly use the rcu operations, we could just go back to wrapping > normal operations in a spin_lock, now that we have a method that's > not > excessively complicated, and would only require holding the lock for > simple variable manipulations. OK, it's not strictly necessary then. Thanks for checking. I wouldn't prefer going back to spinlocks. I think the atomic operations are a step in the right direction. Martin -- Dr. Martin Wilck <mwilck@xxxxxxxx>, Tel. +49 (0)911 74053 2107 SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
