Messages in this thread |  | | | Subject | Re: [PATCH] NTP: remove clock_was_set() call to prevent deadlock | | From | Thomas Gleixner <> | | Date | Wed, 04 Jul 2007 13:15:16 +0200 |
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On Wed, 2007-07-04 at 13:06 +0200, Roman Zippel wrote: > Hi, > > On Tuesday 03 July 2007, Thomas Gleixner 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. > > That's a bit of an easy solution and doesn't fix the real problem. The > clock_was_set() calls were correct, what's broken is the locking. Why wasn't > that fixed instead? > I would at least like to see a comment there, why these calls were removed.
We can not fix the locking that late in the cycle. I doubt that we can fix it at all, as smp_call_function _must_ run with interrupts enabled, therefor it can not run in interrupt context. It needs to run from thread context only.
tglx
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