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| author | Thomas Gleixner <tglx@linutronix.de> | 2007-07-03 20:05:20 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-03 13:54:27 -0700 |
| commit | 746976a301ac9c9aa10d7d42454f8d6cdad8ff2b (patch) | |
| tree | 8173b3b64542b81d94dbb4614b42db66fffbc4d2 /kernel | |
| parent | 872aad45d6174570dd2e1defc3efee50f2cfcc72 (diff) | |
| download | linux-746976a301ac9c9aa10d7d42454f8d6cdad8ff2b.tar.gz linux-746976a301ac9c9aa10d7d42454f8d6cdad8ff2b.tar.bz2 linux-746976a301ac9c9aa10d7d42454f8d6cdad8ff2b.zip | |
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')
| -rw-r--r-- | kernel/time/ntp.c | 2 |
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"); } |