Messages in this thread | | | Date | Sat, 05 Nov 2011 15:58:24 +0530 | From | "Srivatsa S. Bhat" <> | Subject | Re: [PATCH 2/9] kernel/cpu.c: Add arch dependent cpu map update functions |
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On 11/05/2011 03:33 AM, Fenghua Yu wrote: > From: Fenghua Yu <fenghua.yu@intel.com> > > Because resume from hibernate and suspend always starts from CPU0 on x86 BIOS, > we need to check if CPU0 is online before hibernate or suspend. This causes a > race condition on cpu_online_map. > > To cope with the race condition, we add arch_cpu_maps_update_begin() and > arch_cpu_maps_update_done() during cpu_down() and cpu_up(). The functions are > empty on non x86 platforms and are overriden on x86 platforms with real > functions to deal with the race condition. >
The race between CPU Hotplug and suspend/hibernate has been taken care of by my patch here (for another usecase): https://lkml.org/lkml/2011/11/2/487 This is not yet in mainline, but in linux-pm/linux-next. Please see if this solves your case too. And please CC linux-pm mailing list (linux-pm@vger.kernel.org) on patches related to power management.
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> > --- > kernel/cpu.c | 12 ++++++++++++ > 1 files changed, 12 insertions(+), 0 deletions(-) > > diff --git a/kernel/cpu.c b/kernel/cpu.c > index 12b7458..4d80365 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -20,6 +20,14 @@ > /* Serializes the updates to cpu_online_mask, cpu_present_mask */ > static DEFINE_MUTEX(cpu_add_remove_lock); > > +void __weak arch_cpu_maps_update_begin(void) > +{ > +} > + > +void __weak arch_cpu_maps_update_done(void) > +{ > +} > + > /* > * The following two API's must be used when attempting > * to serialize the updates to cpu_online_mask, cpu_present_mask. > @@ -274,6 +282,7 @@ int __ref cpu_down(unsigned int cpu) > int err; > > cpu_maps_update_begin(); > + arch_cpu_maps_update_begin(); > > if (cpu_hotplug_disabled) { > err = -EBUSY; > @@ -284,6 +293,7 @@ int __ref cpu_down(unsigned int cpu) > > out: > cpu_maps_update_done(); > + arch_cpu_maps_update_done(); > return err; > }
See my comments above about whether this is really necessary. By the way, the locking/unlocking order here seems rather weird to me. Why have you not chosen to do something like:
cpu_maps_update_begin() arch_cpu_maps_update_begin() ... arch_cpu_maps_update_done() cpu_maps_update_done()
> EXPORT_SYMBOL(cpu_down); > @@ -367,6 +377,7 @@ int __cpuinit cpu_up(unsigned int cpu) > #endif > > cpu_maps_update_begin(); > + arch_cpu_maps_update_begin(); > > if (cpu_hotplug_disabled) { > err = -EBUSY; > @@ -377,6 +388,7 @@ int __cpuinit cpu_up(unsigned int cpu) > > out: > cpu_maps_update_done(); > + arch_cpu_maps_update_done(); > return err;
Same here. See my comments above.
Thanks, Srivatsa S. Bhat
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