On Wed, May 07, 2014 at 05:17:35PM +0200, Peter Zijlstra wrote: > On Mon, May 05, 2014 at 05:34:08PM +0200, Frederic Weisbecker wrote: > > On Mon, May 05, 2014 at 05:12:28PM +0200, Peter Zijlstra wrote: > > > > Note the current ordering: > > > > > > > > cmpxchg(&qsd->pending, 0, 1) get ipi > > > > csd_lock(qsd->csd) xchg(&qsd->pending, 1) > > > > send ipi csd_unlock(qsd->csd) > > > > > > > > > > > > So there shouldn't be racing updaters. Also ipi sender shouldn't > > > > race with ipi receiver, the update shouldn't always eventually see > > > > the unlock happening. > > > > > > Yeah, I've not spotted how this particular train wreck happens either. > > > > > > The problem is reproduction, it took me 9 hours to confirm I could > > > reproduce the problem on my machine. So how long to I run it with this > > > patch reverted to show its gone.. > > > > Maybe it could be favoured cpu hotplug. Anyway converting to irq_work should > > fix it. > > Ingo needs a commit msg for the revert of this patch; do you think you > have time to look into _why_ this patch is broken and write such a > thing? I can try but I need to reproduce it. Do you have any clue on how to do so? Also which HEAD were you guys using? Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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