Messages in this thread | | | Date | Wed, 2 Nov 2011 17:21:23 +0200 | From | Gleb Natapov <> | Subject | Re: [PATCH] jump_label_inc may return before the code is patched |
| |
On Tue, Oct 18, 2011 at 05:06:25PM -0400, Steven Rostedt wrote: > On Tue, 2011-10-18 at 19:55 +0200, Gleb Natapov wrote: > > If cpu A calls jump_label_inc() just after atomic_add_return() is > > called by cpu B, atomic_inc_not_zero() will return value greater then > > zero and jump_label_inc() will return to a caller before jump_label_update() > > finishes its job on cpu B. > > OK, I see what you are saying. There's a race here that jump_label_inc > may return before jump labels are actually activated. I have no issue > with this change. This guarantees that jump labels will be active on > return of jump_label_inc(). > > I'm assuming that jump_label_update() does memory barries, as it does > modify code, and would be itself a synchronization point. > > Acked-by: Steven Rostedt <rostedt@goodmis.org> > So through what tree this should go to Linus' git?
> -- Steve > > > > > Signed-off-by: Gleb Natapov <gleb@redhat.com> > > diff --git a/kernel/jump_label.c b/kernel/jump_label.c > > index a8ce450..e6f1f24 100644 > > --- a/kernel/jump_label.c > > +++ b/kernel/jump_label.c > > @@ -66,8 +66,9 @@ void jump_label_inc(struct jump_label_key *key) > > return; > > > > jump_label_lock(); > > - if (atomic_add_return(1, &key->enabled) == 1) > > + if (atomic_read(&key->enabled) == 0) > > jump_label_update(key, JUMP_LABEL_ENABLE); > > + atomic_inc(&key->enabled); > > jump_label_unlock(); > > } > > > > -- > > Gleb. >
-- Gleb.
| |