[PATCH 5/8] nohz: Fix notifier return val that enforce timekeeping

From: Frederic Weisbecker
Date: Mon May 20 2013 - 12:02:23 EST

From: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>

In tick_nohz_cpu_down_callback() if the cpu is the one handling
timekeeping , we must return something that stops the CPU_DOWN_PREPARE
notifiers and then start notify CPU_DOWN_FAILED on the already called
notifier call backs.

However traditional errno values are not handled by the notifier unless
these are encapsulated using errno_to_notifier().

Hence the current -EINVAL is misinterpreted and converted to junk after
notifier_to_errno(), leaving the notifier subsystem to random behaviour
such as eventually allowing the cpu to go down.

Fix this by using the standard NOTIFY_BAD instead.

Signed-off-by: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
kernel/time/tick-sched.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index cfc798b..58d8d4d 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -311,7 +311,7 @@ static int __cpuinit tick_nohz_cpu_down_callback(struct notifier_block *nfb,
* we can't safely shutdown that CPU.
if (have_nohz_full_mask && tick_do_timer_cpu == cpu)
- return -EINVAL;
+ return NOTIFY_BAD;
return NOTIFY_OK;

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