Messages in this thread | | | Date | Tue, 8 Apr 2008 00:35:40 +0200 | From | Andi Kleen <> | Subject | Re: BUG: using smp_processor_id() during suspend with 2.6.25-rc8 |
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On Tue, Apr 08, 2008 at 12:29:30AM +0200, Rafael J. Wysocki wrote: > On Tuesday, 8 of April 2008, Andi Kleen wrote: > > On Tue, Apr 08, 2008 at 12:11:17AM +0200, Jiri Kosina wrote: > > > On Tue, 8 Apr 2008, Andi Kleen wrote: > > > > > > > > I know. However preempt_count is a little bit inconsistent in such cases > > > > > though. > > > > And? interrupts off beats preempt count anyways. Why did you write the > > > > patch? Was there a (incorrect) warning triggered? > > > > > > Reported at http://lkml.org/lkml/2008/4/7/130 > > > > > > BTW is also mce_init() (called from mce_resume()) guaranteed to run with > > > IRQs off? > > > > [cc rafael] > > > > The mce resume is a sysdev. > > > > sysdevs were always supposed to run completely with interrupts off. If they > > don't anymore that's some kind of higher level resume code bug which you need > > to fix there, not hack around in the low level code. > > They are executed with interrupts disabled, on one CPU.
Well then someone enables them incorrectly, see the report above.
> > > If it does that it likely broke more code too. > > > > Obviously turning on preemption anywhere around the machine check is > > fatal because it touches CPU state and if you reschedule you could > > switch to another CPU and change or access the wrong CPU's state. > > FWIW, at the point when sysdevs are resumed we are single-threaded.
You mean single CPUed? Even a single thread could switch to another CPU.
-Andi
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