arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c: avoid cross-CPU interrupts by using smp_c...

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>

diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
index f28decf8dde3990626f493e5d962bfea9d48e59f..1b1920fa7c8085934cbd846e9329cc538c25be4b 100644 (file)
--- 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)