3.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Andreas Herrmann <andreas.herrma...@amd.com>
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.herrma...@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/cpufreq/powernow-k8.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
--- a/drivers/cpufreq/powernow-k8.c
+++ b/drivers/cpufreq/powernow-k8.c
@@ -1223,14 +1223,7 @@ static int powernowk8_target(struct cpuf
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 */
--
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