diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2013-06-26 12:17:32 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2013-07-02 14:26:44 +0200 |
| commit | c9b5a266b103af873abb9ac03bc3d067702c8f4b (patch) | |
| tree | 91e5ec118a7e96b998e18a8601d8f14c76d94823 /kernel/time | |
| parent | 47433b8c9d7480a3eebd99df38e857ce85a37cee (diff) | |
| download | linux-c9b5a266b103af873abb9ac03bc3d067702c8f4b.tar.bz2 | |
tick: Make oneshot broadcast robust vs. CPU offlining
In periodic mode we remove offline cpus from the broadcast propagation
mask. In oneshot mode we fail to do so. This was not a problem so far,
but the recent changes to the broadcast propagation introduced a
constellation which can result in a NULL pointer dereference.
What happens is:
CPU0 CPU1
idle()
arch_idle()
tick_broadcast_oneshot_control(OFF);
set cpu1 in tick_broadcast_force_mask
if (cpu_offline())
arch_cpu_dead()
cpu_dead_cleanup(cpu1)
cpu1 tickdevice pointer = NULL
broadcast interrupt
dereference cpu1 tickdevice pointer -> OOPS
We dereference the pointer because cpu1 is still set in
tick_broadcast_force_mask and tick_do_broadcast() expects a valid
cpumask and therefor lacks any further checks.
Remove the cpu from the tick_broadcast_force_mask before we set the
tick device pointer to NULL. Also add a sanity check to the oneshot
broadcast function, so we can detect such issues w/o crashing the
machine.
Reported-by: Prarit Bhargava <prarit@redhat.com>
Cc: athorlton@sgi.com
Cc: CAI Qian <caiqian@redhat.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1306261303260.4013@ionos.tec.linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/tick-broadcast.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index d067c01586f5..4790037163f6 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -533,6 +533,13 @@ again: cpumask_clear(tick_broadcast_force_mask); /* + * Sanity check. Catch the case where we try to broadcast to + * offline cpus. + */ + if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask))) + cpumask_and(tmpmask, tmpmask, cpu_online_mask); + + /* * Wakeup the cpus which have an expired event. */ tick_do_broadcast(tmpmask); @@ -773,10 +780,12 @@ void tick_shutdown_broadcast_oneshot(unsigned int *cpup) raw_spin_lock_irqsave(&tick_broadcast_lock, flags); /* - * Clear the broadcast mask flag for the dead cpu, but do not - * stop the broadcast device! + * Clear the broadcast masks for the dead cpu, but do not stop + * the broadcast device! */ cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask); + cpumask_clear_cpu(cpu, tick_broadcast_pending_mask); + cpumask_clear_cpu(cpu, tick_broadcast_force_mask); raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); } |