On 11/23, Peter Zijlstra wrote: > > On Tue, 2010-11-23 at 16:08 +0100, Oleg Nesterov wrote: > > > Ah,. uhm,. you mean, not do anything at all? > > > > > > Dunno, really, let me try and read the code there. > > > > Thanks. This is very minor of course, but it would be nice to > > undestand the reason. To me it looks unneeded, but I don't trust > > myself. (snippets from my previous email below). > > > I think because the call to __cpu_die (-> native_cpu_die) relies on the > remote cpu running the idle thread, How? It can't. By the time __cpu_die() is called, we do not even know whether context_switch() was finished. All we know is that rq->curr = idle. native_cpu_die() correctly waits in a loop until the idle thread sets CPU_DEAD. And I think every smp_ops->cpu_die() implementation should synhcronize with ->cpu_disable(), otherwise it is buggy. > and the CPU_DEAD notifier callback > wants to run with the guarantee the remote cpu is in fact dead as a > doornail. I think __cpu_die() should ensure it is dead. OK. This is really minor. Perhaps it is safer to keep this wait just to preserve the current behaviour. Oleg. -- 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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