From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e36.co.us.ibm.com (e36.co.us.ibm.com [32.97.110.154]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e36.co.us.ibm.com", Issuer "Equifax" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 8DB51B7005 for ; Sun, 17 Jun 2012 02:32:57 +1000 (EST) Received: from /spool/local by e36.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 16 Jun 2012 10:32:55 -0600 Received: from d03relay03.boulder.ibm.com (d03relay03.boulder.ibm.com [9.17.195.228]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 6E29619D8052 for ; Sat, 16 Jun 2012 16:32:22 +0000 (WET) Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay03.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q5GGWOBx178236 for ; Sat, 16 Jun 2012 10:32:24 -0600 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q5GGWLqo015210 for ; Sat, 16 Jun 2012 10:32:24 -0600 Date: Sat, 16 Jun 2012 09:32:19 -0700 From: "Paul E. McKenney" To: Yong Zhang 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> 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 In-Reply-To: <1338275765-3217-10-git-send-email-yong.zhang0@gmail.com> Cc: axboe@kernel.dk, nikunj@linux.vnet.ibm.com, sshtylyov@mvista.com, david.daney@cavium.com, peterz@infradead.org, linux-kernel@vger.kernel.org, ralf@linux-mips.org, akpm@linux-foundation.org, Paul Mackerras , srivatsa.bhat@linux.vnet.ibm.com, tglx@linutronix.de, linuxppc-dev@lists.ozlabs.org, mingo@kernel.org Reply-To: paulmck@linux.vnet.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 >