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27 March 2024, 02:37:15 UTC
Revision 746976a301ac9c9aa10d7d42454f8d6cdad8ff2b authored by Thomas Gleixner on 03 July 2007, 18:05:20 UTC, committed by Linus Torvalds on 03 July 2007, 20:54:27 UTC 
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 parent 872aad4
History
Tip revision: 746976a301ac9c9aa10d7d42454f8d6cdad8ff2b authored by Thomas Gleixner on 03 July 2007, 18:05:20 UTC
NTP: remove clock_was_set() call to prevent deadlock
Tip revision: 746976a
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.gitignore -rw-r--r-- 572 bytes
.mailmap -rw-r--r-- 3.6 KB
COPYING -rw-r--r-- 18.3 KB
CREDITS -rw-r--r-- 89.3 KB
Kbuild -rw-r--r-- 1.5 KB
MAINTAINERS -rw-r--r-- 87.8 KB
Makefile -rw-r--r-- 49.2 KB
README -rw-r--r-- 16.5 KB
REPORTING-BUGS -rw-r--r-- 3.0 KB

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