Re: [PATCH -mm] markers: avoid call_rcu_sched if old is NULL

Mathieu Desnoyers
2008-07-13T04:28:21Z

* Andrew Morton (akpm@linux-foundation.org) wrote:
> On Tue, 8 Jul 2008 23:02:01 -0400 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
>
> > * Masami Hiramatsu (mhiramat@redhat.com) wrote:
> > > Introduce marker_entry_free_old() and check old pointer is NULL before
> > > setting call_rcu_sched(), because marker_entry_remove/add_probe() can
> > > return NULL.
> > >
> >
> > Hi Masami,
> >
> > I doubt this is a bug per se, because kfree accepts NULL pointers (and
> > kfree is the only action done on the oldptr by free_old_closure).
> >
> > This cleans up the code, so I think it's good to merge your patch, but I
> > would definitely not classify this as a bugfix.
> >
> > Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
>
> I cannot get this to apply on the rather dated tree which I have on this
> rather not-on-the-internet machine. Please merge this patch locally, test,
> rewrite the changelog and resend it to someone ;)
>

Hi Andrew,

As I pointed out in a reply to this email, I NACK this patch because it
removes a necessary quiescent state wait from the marker code. The other
reply here explains why I changed my mind about this patch.