Re: [PATCH] NTP: remove clock_was_set() call to prevent deadlock

[Ingo Molnar]

* Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:

> 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/
> 
> 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@xxxxxxxxxxxxx>

looks good to me.

Acked-by: Ingo Molnar <mingo@xxxxxxx>

	Ingo
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