• Thomas Gleixner's avatar
    NTP: remove clock_was_set() call to prevent deadlock · 746976a3
    Thomas Gleixner authored
    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: default avatarThomas Gleixner <tglx@linutronix.de>
    Acked-by: default avatarIngo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    746976a3
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