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Date: Sat, 05 Nov 2011 15:58:24 +0530 From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> To: Fenghua Yu <fenghua.yu@...el.com> CC: Thomas Gleixner <tglx@...utronix.de>, H Peter Anvin <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>, Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, Tony Luck <tony.luck@...el.com>, Suresh B Siddha <suresh.b.siddha@...el.com>, Len Brown <len.brown@...el.com>, Peter Zijlstra <peterz@...radead.org>, linux-kernel <linux-kernel@...r.kernel.org>, Linux PM mailing list <linux-pm@...r.kernel.org> Subject: Re: [PATCH 2/9] kernel/cpu.c: Add arch dependent cpu map update functions On 11/05/2011 03:33 AM, Fenghua Yu wrote: > From: Fenghua Yu <fenghua.yu@...el.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@...r.kernel.org) on patches related to power management. > Signed-off-by: Fenghua Yu <fenghua.yu@...el.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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