From 4a28395d72a956f2dad24e343d06bc08c9afb89a Mon Sep 17 00:00:00 2001
From: Andrew Morton <akpm@linux-foundation.org>
Date: Mon, 21 Dec 2009 16:19:58 -0800
Subject: [PATCH] arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c: avoid cross-CPU
interrupts by using smp_call_function_any()
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" <yanmin_zhang@linux.intel.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jaswinder Singh Rajput <jaswinder@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
---
arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
index f28decf8dde39..1b1920fa7c808 100644
--- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
+++ b/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)
--
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