Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755111Ab2FPQc5 (ORCPT ); Sat, 16 Jun 2012 12:32:57 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:40334 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753196Ab2FPQc4 (ORCPT ); Sat, 16 Jun 2012 12:32:56 -0400 Date: Sat, 16 Jun 2012 09:32:19 -0700 From: "Paul E. McKenney" To: Yong Zhang Cc: linux-kernel@vger.kernel.org, ralf@linux-mips.org, sshtylyov@mvista.com, david.daney@cavium.com, nikunj@linux.vnet.ibm.com, axboe@kernel.dk, mingo@kernel.org, tglx@linutronix.de, peterz@infradead.org, akpm@linux-foundation.org, srivatsa.bhat@linux.vnet.ibm.com, Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org Subject: Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock() Message-ID: <20120616163219.GI2420@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1338275765-3217-1-git-send-email-yong.zhang0@gmail.com> <1338275765-3217-10-git-send-email-yong.zhang0@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1338275765-3217-10-git-send-email-yong.zhang0@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12061616-7408-0000-0000-000005E9217E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1975 Lines: 56 On Tue, May 29, 2012 at 03:16:04PM +0800, Yong Zhang wrote: > From: Yong Zhang > > 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 > Cc: Benjamin Herrenschmidt > Cc: Paul Mackerras > 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/