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authorThomas Gleixner <tglx@linutronix.de>2007-07-03 20:05:20 +0200
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-03 13:54:27 -0700
commit746976a301ac9c9aa10d7d42454f8d6cdad8ff2b (patch)
tree8173b3b64542b81d94dbb4614b42db66fffbc4d2 /kernel/time
parent872aad45d6174570dd2e1defc3efee50f2cfcc72 (diff)
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>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/ntp.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 87aa5ff931e..cf53bb5814c 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");
}