NTP: remove clock_was_set() call to prevent deadlock

The clock_was_set() call in seconds_overflow() which happens only when
leap seconds are inserted / deleted is wrong in two aspects:

1. it results in a call to on_each_cpu() with interrupts disabled
2. it is potential deadlock source vs. call_lock in smp_call_function()

The only possible side effect of the removal might be, that an absolute
CLOCK_REALTIME timer fires 1 second too late, in the rare case of leap
second deletion and an absolute CLOCK_REALTIME timer which expires in
the affected time frame. It will never fire too early.

This was probably observed by the reporter of a June 30th -> July 1st
hang: http://lkml.org/lkml/2007/7/3/103

A similar problem was observed by Dave Jones, who provided a screen shot
with a lockdep back trace, which allowed to analyse the problem.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 2 deletions

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 87aa5ff931e0..cf53bb5814cb 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -122,7 +122,6 @@ void second_overflow(void)
                          */
                         time_interpolator_update(-NSEC_PER_SEC);
                         time_state = TIME_OOP;
-                        clock_was_set();
                         printk(KERN_NOTICE "Clock: inserting leap second "
                                         "23:59:60 UTC\n");
                 }
@@ -137,7 +136,6 @@ void second_overflow(void)
                          */
                         time_interpolator_update(NSEC_PER_SEC);
                         time_state = TIME_WAIT;
-                        clock_was_set();
                         printk(KERN_NOTICE "Clock: deleting leap second "
                                         "23:59:59 UTC\n");
                 }