Messages in this thread | | | Date | Mon, 18 Jun 2012 10:51:59 +0800 | From | Yong Zhang <> | Subject | Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock() |
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On Sat, Jun 16, 2012 at 09:32:19AM -0700, Paul E. McKenney wrote: > On Tue, May 29, 2012 at 03:16:04PM +0800, Yong Zhang wrote: > > From: Yong Zhang <yong.zhang@windriver.com> > > > > 1) call_function.lock used in smp_call_function_many() is just to protect > > call_function.queue and &data->refs, cpu_online_mask is outside of the > > lock. And it's not necessary to protect cpu_online_mask, > > because data->cpumask is pre-calculate and even if a cpu is brougt up > > when calling arch_send_call_function_ipi_mask(), it's harmless because > > validation test in generic_smp_call_function_interrupt() will take care > > of it. > > > > 2) For cpu down issue, stop_machine() will guarantee that no concurrent > > smp_call_fuction() is processing. > > However, there is an effort to get rid of stop_machine() from the > CPU-down path... So something else will be needed.
Yeah. So Thomas changed the commit log like below: [ ipi_call_lock/unlock() lock resp. unlock call_function.lock. This lock protects only the call_function data structure itself, but it's completely unrelated to cpu_online_mask. The mask to which the IPIs are sent is calculated before call_function.lock is taken in smp_call_function_many(), so the locking around set_cpu_online() is pointless and can be removed.
[ tglx: Massaged changelog ] ]
in tip/smp/hotplug.
Thanks, Yong
> > Thanx, Paul > > > Signed-off-by: Yong Zhang <yong.zhang0@gmail.com> > > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > > Cc: Paul Mackerras <paulus@samba.org> > > Cc: linuxppc-dev@lists.ozlabs.org > > --- > > arch/powerpc/kernel/smp.c | 2 -- > > 1 files changed, 0 insertions(+), 2 deletions(-) > > > > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c > > index e4cb343..e1417c4 100644 > > --- a/arch/powerpc/kernel/smp.c > > +++ b/arch/powerpc/kernel/smp.c > > @@ -571,7 +571,6 @@ void __devinit start_secondary(void *unused) > > if (system_state == SYSTEM_RUNNING) > > vdso_data->processorCount++; > > #endif > > - ipi_call_lock(); > > notify_cpu_starting(cpu); > > set_cpu_online(cpu, true); > > /* Update sibling maps */ > > @@ -601,7 +600,6 @@ void __devinit start_secondary(void *unused) > > of_node_put(np); > > } > > of_node_put(l2_cache); > > - ipi_call_unlock(); > > > > local_irq_enable(); > > > > -- > > 1.7.5.4 > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
-- Only stand for myself
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