Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: BUG: using smp_processor_id() during suspend with 2.6.25-rc8 | Date | Tue, 8 Apr 2008 00:56:32 +0200 |
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On Tuesday, 8 of April 2008, Jiri Kosina wrote: > On Tue, 8 Apr 2008, Rafael J. Wysocki wrote: > > > > 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. > > So, any idea why mce_resume() -> mce_init() -> debug_smp_processor_id() > triggers the warning? Apparently preempt_count is zero, irqs_disabled() > returns false, and cpumask_of_cpu() is not equal to current->cpus_allowed. > > So there clearly is a bug somewhere.
Yes, there is. Still, I wonder why doesn't everyone see it.
> > > 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. > > Is that really relevant here? We still could be switched over to another > CPU, and that would break things.
No, we couldn't, because the other CPUs are off at this point.
Thanks, Rafael
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