Messages in this thread | | | Date | Sat, 6 Jun 2009 11:24:50 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH] tick: add check for the existence of broadcast clock event device |
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On Fri, 5 Jun 2009, Feng Tang wrote:
> >From 2f076e1867c8bbb145b74d289358174644d9fed8 Mon Sep 17 00:00:00 2001 > From: Feng Tang <feng.tang@intel.com> > Date: Fri, 5 Jun 2009 10:36:15 +0800 > Subject: [PATCH] tick: add check for the existence of broadcast clock event device > > Some platform may have no broadcast clock event device, as it use always-on > external timers for per-cpu timer and has no extra one for broadcast device. > This check will secure the access to bc device when system get some boradcast > on/off and enter/exit message > > Signed-off-by: Feng Tang <feng.tang@intel.com> > --- > kernel/time/tick-broadcast.c | 8 +++++++- > 1 files changed, 7 insertions(+), 1 deletions(-) > > diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c > index 118a3b3..110e0bc 100644 > --- a/kernel/time/tick-broadcast.c > +++ b/kernel/time/tick-broadcast.c > @@ -214,10 +214,13 @@ static void tick_do_broadcast_on_off(void *why) > > spin_lock_irqsave(&tick_broadcast_lock, flags); > > + bc = tick_broadcast_device.evtdev; > + if (!bc) > + goto out; > +
This check is not necessary because we check whether the percpu device is affected by the stops in C3 madness _before_ we touch the broadcast device.
if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP)) got out;
If your percpu devices are always on (not affected by C3 stop) then you never dereference bc. So why do we need an extra check for !bc ?
Thanks,
tglx
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