[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20120524171524.GG6908@n2100.arm.linux.org.uk>
Date: Thu, 24 May 2012 18:15:24 +0100
From: Russell King - ARM Linux <linux@....linux.org.uk>
To: Pantelis Antoniou <panto@...oniou-consulting.com>
Cc: linux-kernel@...r.kernel.org, Russ.Dill@...com, mporter@...com,
stable@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] [ARM] Unconditional call to smp_cross_call on UP
crashes
On Thu, May 24, 2012 at 07:55:56PM +0300, Pantelis Antoniou wrote:
> Hi Russell,
>
> On May 24, 2012, at 7:17 PM, Russell King - ARM Linux wrote:
>
> > On Thu, May 24, 2012 at 07:50:24PM +0000, Pantelis Antoniou wrote:
> >> omap2plus_defconfig builds with SMP & SMP_ON_UP set.
> >> On beagle (which is UP) is_smp() returns false and we don't call
> >> smp_init_cpus which in turn does not initialize smp_cross_call which
> >> remains NULL.
> >>
> >> When issuing a reboot we OOPS with a NULL dereference on stop smp_call.
> >
> > I've been wondering whether we should make smp_cross_call() a no-op instead
> > by default, rather than a NULL pointer.
> >
> > Alternatively, if may be well worth changing this to do:
> >
> > if (!cpumask_empty(&mask))
> > smp_cross_call(&mask, IPI_CPU_STOP);
> >
> > instead, so we avoid calling smp_cross_call() when we're on a SMP system
> > with only one CPU online. I like this approach better because it removes
> > a potential call into platform code which is inappropriate.
>
> Both of these can work, and in fact have been tried.
>
> I am partial on both to be honest. Have a default no-op function for smp_cross_call()
> and guard with cpumask_empty().
>
> Which do you want me to make a patch for?
I think the cpumask_empty() is the best approach, thanks.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists