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.

Ben

> 
> Martin
> 
> -- 
> Dr. Martin Wilck <mwi...@suse.com>, Tel. +49 (0)911 74053 2107
> SUSE Linux GmbH, GF: Felix Imend├Ârffer, Jane Smithard, Graham Norton
> HRB 21284 (AG N├╝rnberg)

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