Messages in this thread | | | Date | Thu, 3 Oct 2013 09:42:05 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 2/3] rcu: Create rcu_sync infrastructure |
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On Wed, Oct 02, 2013 at 05:49:01PM +0200, Oleg Nesterov wrote: > On 10/02, Peter Zijlstra wrote: > > > > From: Oleg Nesterov <oleg@redhat.com> > > Thanks! I was writing the patch, and I chose almost the same naming ;) > > > Signed-off-by: Peter Zijlstra <peterz@infradead.org> > > Signed-off-by: Oleg Nesterov <oleg@redhat.com> > > In fact I'd like to add my sob to 1/3 and 3/3 as well. > > > Paul, to remind, this is only the first step. I am going to send > the following improvements: > > 1. Add rcu_sync->exlusive. The change is simple, just we > need s/wait_queue_head_t/completion/ in rcu_sync_struct > and a couple of "if (rss->exclusive)" checks in enter/exit. > > 2. rcu_sync_enter() should return !!need_sync. This can help > in exclusive mode. > > 3. rcu_sync_struct needs more function pointers (perhaps we > should add a single rcu_sync_struct->ops pointer but this > is minor). See below. > > But let me repeat just in case, we should do this later. > And once this series is applied, I'll change percpu_rw_semaphore.
I took this into account in my review, the upgrades would be good! ;-)
Thanx, Paul
> > +struct rcu_sync_struct { > > + int gp_state; > > + int gp_count; > > + wait_queue_head_t gp_wait; > > + > > + int cb_state; > > + struct rcu_head cb_head; > > + > > + void (*sync)(void); > > + void (*call)(struct rcu_head *, void (*)(struct rcu_head *)); > > Yes, and we also need rcu_sync_struct->barrier(). From the patch I was > working on: > > void rcu_sync_wait_for_callback(struct rcu_sync *sync) > { > int cb_state; > > BUG_ON(sync->gp_count); > > spin_lock_irq(&sync->state_lock); > if (sync->cb_state == CB_REPLAY) > sync->cb_state = CB_PENDING; > cb_state = sync->cb_state; > spin_unlock_irq(&sync->state_lock); > > if (cb_state != CB_IDLE) { > rcu_barrier_sched(); > BUG_ON(sync->cb_state != CB_IDLE); > } > } > > It should be called if you are going to kfree the object. > > Perhaps another rcu_sync_struct->state_change(new_state) callback (set > by the user) makes sense too, this can help (for example) to implement > the array of semaphores with a single rcu_sync_struct (freeze_super). > > Thanks. > > Oleg. >
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