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SubjectRe: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
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.

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
>



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