On 07/01/2012 11:36 AM, John Stultz wrote: > I believe this issue is due to the leapsecond being added without > calling clock_was_set() to notify the hrtimer subsystem of the > change. (Although I've not yet chased all the way down to the > hrtimer code to validate exactly what's going on there).
For the benefit of -stable: Am I right in thinking that, if the analysis is confirmed, this was caused by the following commit: commit 746976a301ac9c9aa10d7d42454f8d6cdad8ff2b Author: Thomas Gleixner <[email protected]> Date: Tue Jul 3 20:05:20 2007 +0200 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. Sob: Thomas Gleixner <[email protected]> Ab: Ingo Molnar <[email protected]> Sob: Linus Torvalds <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
