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

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Submitter Herton Ronaldo Krzesinski
Date Nov. 22, 2012, 4:47 a.m.
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Download mbox | patch
Permalink /patch/200962/
State New
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Herton Ronaldo Krzesinski - Nov. 22, 2012, 4:47 a.m.
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:;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



From 83a5958c6333dfafe31e9eefe91a7f18effaff62 Mon Sep 17 00:00:00 2001
From: Andreas Herrmann <>
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 <>
Signed-off-by: Rafael J. Wysocki <>
Signed-off-by: Herton Ronaldo Krzesinski <>
 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 */