Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
From: Paul E. McKenney <hidden>
Date: 2012-06-16 16:32:57
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On Tue, May 29, 2012 at 03:16:04PM +0800, Yong Zhang wrote:
From: Yong Zhang <redacted> 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
quoted hunk ↗ jump to hunk
Signed-off-by: Yong Zhang <redacted> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <redacted> 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