ARM: arch_timer: Silence debug preempt warnings

Hot-plugging with CONFIG_DEBUG_PREEMPT=y on a device with arm
architected timers causes a slew of "using smp_processor_id() in
preemptible" warnings:

  BUG: using smp_processor_id() in preemptible [00000000] code: sh/111
  caller is arch_timer_cpu_notify+0x14/0xc8

This happens because sometimes the cpu notifier,
arch_timer_cpu_notify(), is called in preemptible context and
other times in non-preemptible context but we use this_cpu_ptr()
to retrieve the clockevent in all cases. We're only going to
actually use the pointer in non-preemptible context though, so
push the this_cpu_ptr() access down into the cases to force the
checks to occur only in non-preemptible contexts.

Cc: John Stultz <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Mark Rutland <[email protected]>
Acked-by: Marc Zyngier <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
Signed-off-by: Olof Johansson <[email protected]>

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 122ff05628b5b7419d47b5368719234d9c7d352f..a2b25418978244d1ae129cf74f031020951f35d4 100644 (file)
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -248,14 +248,16 @@ static void __cpuinit arch_timer_stop(struct clock_event_device *clk)
 static int __cpuinit arch_timer_cpu_notify(struct notifier_block *self,
                                           unsigned long action, void *hcpu)
 {
-       struct clock_event_device *evt = this_cpu_ptr(arch_timer_evt);
-
+       /*
+        * Grab cpu pointer in each case to avoid spurious
+        * preemptible warnings
+        */
        switch (action & ~CPU_TASKS_FROZEN) {
        case CPU_STARTING:
-               arch_timer_setup(evt);
+               arch_timer_setup(this_cpu_ptr(arch_timer_evt));
                break;
        case CPU_DYING:
-               arch_timer_stop(evt);
+               arch_timer_stop(this_cpu_ptr(arch_timer_evt));
                break;
        }