[ 3.5.yuz extended stable ] Patch "cpufreq / powernow-k8: Remove usage of smp_processor_id() in" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    cpufreq / powernow-k8: Remove usage of smp_processor_id() in

to the linux-3.5.y-queue branch of the 3.5.yuz extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.yuz tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From 83a5958c6333dfafe31e9eefe91a7f18effaff62 Mon Sep 17 00:00:00 2001
From: Andreas Herrmann <andreas.herrmann3 at amd.com>
Date: Tue, 23 Oct 2012 00:55:10 +0200
Subject: [PATCH] cpufreq / powernow-k8: Remove usage of smp_processor_id() in
 preemptible code

commit e4df1cbcc1f329e53a1fff7450b2229e0addff20 upstream.

Commit 6889125b8b4e09c5e53e6ecab3433bed1ce198c9
(cpufreq/powernow-k8: workqueue user shouldn't migrate the kworker to another CPU)
causes powernow-k8 to trigger a preempt warning, e.g.:

  BUG: using smp_processor_id() in preemptible [00000000] code: cpufreq/3776
  caller is powernowk8_target+0x20/0x49
  Pid: 3776, comm: cpufreq Not tainted 3.6.0 #9
  Call Trace:
   [<ffffffff8125b447>] debug_smp_processor_id+0xc7/0xe0
   [<ffffffff814877e7>] powernowk8_target+0x20/0x49
   [<ffffffff81482b02>] __cpufreq_driver_target+0x82/0x8a
   [<ffffffff81484fc6>] cpufreq_governor_performance+0x4e/0x54
   [<ffffffff81482c50>] __cpufreq_governor+0x8c/0xc9
   [<ffffffff81482e6f>] __cpufreq_set_policy+0x1a9/0x21e
   [<ffffffff814839af>] store_scaling_governor+0x16f/0x19b
   [<ffffffff81484f16>] ? cpufreq_update_policy+0x124/0x124
   [<ffffffff8162b4a5>] ? _raw_spin_unlock_irqrestore+0x2c/0x49
   [<ffffffff81483640>] store+0x60/0x88
   [<ffffffff811708c0>] sysfs_write_file+0xf4/0x130
   [<ffffffff8111243b>] vfs_write+0xb5/0x151
   [<ffffffff811126e0>] sys_write+0x4a/0x71
   [<ffffffff816319a9>] system_call_fastpath+0x16/0x1b

Fix this by by always using work_on_cpu().

Signed-off-by: Andreas Herrmann <andreas.herrmann3 at amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 drivers/cpufreq/powernow-k8.c |    9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c
index 1a40935..c671369 100644
--- a/drivers/cpufreq/powernow-k8.c
+++ b/drivers/cpufreq/powernow-k8.c
@@ -1223,14 +1223,7 @@ static int powernowk8_target(struct cpufreq_policy *pol,
 	struct powernowk8_target_arg pta = { .pol = pol, .targfreq = targfreq,
 					     .relation = relation };

-	/*
-	 * Must run on @pol->cpu.  cpufreq core is responsible for ensuring
-	 * that we're bound to the current CPU and pol->cpu stays online.
-	 */
-	if (smp_processor_id() == pol->cpu)
-		return powernowk8_target_fn(&pta);
-	else
-		return work_on_cpu(pol->cpu, powernowk8_target_fn, &pta);
+	return work_on_cpu(pol->cpu, powernowk8_target_fn, &pta);
 }

 /* Driver entry point to verify the policy and range of frequencies */
--
1.7.9.5