From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: [patch 1/9] arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c: avoid cross-CPU interrupts by using smp_call_function_any() Date: Mon, 21 Dec 2009 16:19:58 -0800 Message-ID: <200912220019.nBM0Jwbq004738@imap1.linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:33440 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752226AbZLVAVU (ORCPT ); Mon, 21 Dec 2009 19:21:20 -0500 Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: lenb@kernel.org Cc: linux-acpi@vger.kernel.org, akpm@linux-foundation.org, davej@redhat.com, efault@gmx.de, jaswinder@kernel.org, len.brown@intel.com, mingo@elte.hu, rusty@rustcorp.com.au, tglx@linutronix.de, venkatesh.pallipadi@intel.com, yakui.zhao@intel.com, yanmin_zhang@linux.intel.com From: Andrew Morton Presently acpi-cpufreq will perform the MSR read on the first CPU in the mask. That's inefficient if that CPU differs from the current CPU. Because we have to perform a cross-CPU call, but we could have run the rdmsr on the current CPU. So switch to using the new smp_call_function_any(), which will perform the call on the current CPU if that CPU is present in the mask (it is). Cc: "Zhang, Yanmin" Cc: Dave Jones Cc: Ingo Molnar Cc: Jaswinder Singh Rajput Cc: Len Brown Cc: Mike Galbraith Cc: Rusty Russell Cc: Thomas Gleixner Cc: Venkatesh Pallipadi Cc: Zhao Yakui Signed-off-by: Andrew Morton --- arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff -puN arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c~arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts-by-using-smp_call_function_any arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c --- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c~arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts-by-using-smp_call_function_any +++ a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c @@ -190,9 +190,11 @@ static void do_drv_write(void *_cmd) static void drv_read(struct drv_cmd *cmd) { + int err; cmd->val = 0; - smp_call_function_single(cpumask_any(cmd->mask), do_drv_read, cmd, 1); + err = smp_call_function_any(cmd->mask, do_drv_read, cmd, 1); + WARN_ON_ONCE(err); /* smp_call_function_any() was buggy? */ } static void drv_write(struct drv_cmd *cmd) _