Messages in this thread | | | Date | Thu, 9 Jul 2015 07:21:16 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH RFC tip/core/rcu 05/14] rcu: Abstract sequence counting from synchronize_sched_expedited() |
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On Thu, Jul 09, 2015 at 11:42:49AM +0300, Dan Carpenter wrote: > On Wed, Jul 01, 2015 at 03:18:04PM -0700, Paul E. McKenney wrote: > > > > +/* Adjust sequence number for start of update-side operation. */ > > > > +static void rcu_seq_start(unsigned long *sp) > > > > +{ > > > > + WRITE_ONCE(*sp, *sp + 1); > > > > + smp_mb(); /* Ensure update-side operation after counter increment. */ > > > > + WARN_ON_ONCE(!(*sp & 0x1)); > > > > +} > > > > > > That wants to be an ACQUIRE, right? > > > > I cannot put the acquire in the WARN_ON_ONCE() because there > > are configurations where WARN_ON_ONCE() is compiled out. > > I think WARN_ON_ONCE() always evaulates the condition. You are maybe > thinking of VM_WARN_ON_ONCE().
Even if it happens to now, it is only a matter of time until the tinification people make it optional.
> I'm on a different thread where we almost introduced a bug by using > VM_WARN_ONCE() instead of WARN_ONCE(). The VM_WARNING conditions had > long execute times so they are weird.
New one on me! At first glance, they look like they map pretty directly, though.
Thanx, Paul
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