Messages in this thread | | | Date | Fri, 15 Jul 2016 06:39:28 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob |
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On Fri, Jul 15, 2016 at 03:27:09PM +0200, Oleg Nesterov wrote: > On 07/14, Peter Zijlstra wrote: > > > > On Thu, Jul 14, 2016 at 08:43:51PM +0200, Oleg Nesterov wrote: > > > > > > Oh well... I personally do not think this is what we want... Can't > > > we just add the stupid rcu_sync_enter() into cgroup_init() at least > > > for now? Yes, this means the unnecessary .sync() at boot time, but > > > it will go away after cleanups I am going to send. > > > > Something like so then? > > OK, agreed, > > > --- > > --- a/include/linux/rcu_sync.h > > +++ b/include/linux/rcu_sync.h > > @@ -59,6 +59,7 @@ static inline bool rcu_sync_is_idle(stru > > } > > > > extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type); > > +extern void rcu_sync_sabotage(struct rcu_sync *); > > extern void rcu_sync_enter(struct rcu_sync *); > > extern void rcu_sync_exit(struct rcu_sync *); > > extern void rcu_sync_dtor(struct rcu_sync *); > > --- a/kernel/cgroup.c > > +++ b/kernel/cgroup.c > > @@ -5609,6 +5609,8 @@ int __init cgroup_init(void) > > BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files)); > > BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files)); > > > > + rcu_sync_sabotage(&cgroup_threadgroup_rwsem.rss); > > Heh ;) I too think it should be renamed. I'd suggest > > __rcu_sync_enter(rss); > > although I do not really mind and agree with any name.
Hmmm... Why not just move the checks out into the caller? That would make the intent much more clear.
Thanx, Paul
> Hopefully I'll send some cleanups soon, rcu_sync_enter() will be > re-implemented as > > rcu_sync_enter(rss) > { > if (__rcu_sync_enter(rss)) > __rcu_sync_wait(rss); > } > > > + * rcu_sync_sabotage() - Sabotage a fresh rcu_sync instance > > + * @rsp: Pointer to rcu_sync structure to be sabotaged > > + * > > + * Must be called after rcu_sync_init() and before first use. > > OK. And after those cleanups __rcu_sync_enter() can be called at any > time. > > Oleg. >
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