Messages in this thread | | | Date | Tue, 11 Nov 2008 16:11:51 +0100 | From | "Dmitry Adamushko" <> | Subject | Re: [Bug #11989] Suspend failure on NForce4-based boards due to chanes in stop_machine |
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2008/11/11 Vegard Nossum <vegard.nossum@gmail.com>: > On Tue, Nov 11, 2008 at 11:52 AM, Ingo Molnar <mingo@elte.hu> wrote: >> [ Cc:-ed workqueue/locking/suspend-race-condition experts. ] >> >> Seems like the new kernel/stop_machine.c logic has a race for the test >> sequence above. (Below is the bisected commit again, maybe the race is >> visible via email review as well.) > > I try again. > > I think that the test for stop_machine_data in stop_cpu() should not > have been moved from __stop_machine().
Do you mean the following test?
if (!active_cpus) { if (cpu == first_cpu(cpu_online_map)) smdata = &active; } else { if (cpu_isset(cpu, *active_cpus)) smdata = &active; }
> Because now cpu_online_map may > change in-between calls to stop_cpu() (if the callback tries to > online/offline CPUs), and the end result may be different.
take_cpu_down() may not run earlier than stop_cpu() on all the cpus have completed the STOPMACHINE_DISABLE_IRQ step, iow. "state == STOPMACHINE_RUN". By that moment, 'smdata' has been set up on all cpus... if this is the case you had in mind.
> > Maybe? > > > Vegard >
-- Best regards, Dmitry Adamushko
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