linux-kernel - [PATCH -mm] cpufreq: BUG: using smp_processor

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Message-ID: <48D2BD7C.4070300@gmail.com>
Date:	Thu, 18 Sep 2008 22:43:40 +0200
From:	Andrea Righi <righi.andrea@...il.com>
To:	davej@...emonkey.org.uk, Andrew Morton <akpm@...ux-foundation.org>
CC:	cpufreq@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH -mm] cpufreq: BUG: using smp_processor_id() in preemptible
 code

Use get_cpu()/put_cpu() in cpufreq_ondemand init routine, instead of
smp_processor_id() to avoid the following BUG:

[   35.313118] BUG: using smp_processor_id() in preemptible [00000000] code: modprobe/4952
[   35.313132] caller is cpufreq_gov_dbs_init+0xa/0x8f [cpufreq_ondemand]
[   35.313140] Pid: 4952, comm: modprobe Not tainted 2.6.27-rc5-mm1 #23
[   35.313145] Call Trace:
[   35.313158]  [<ffffffff80361ff7>] debug_smp_processor_id+0xd7/0xe0
[   35.313167]  [<ffffffffa010800a>] cpufreq_gov_dbs_init+0xa/0x8f [cpufreq_ondemand]
[   35.313176]  [<ffffffff8020903b>] _stext+0x3b/0x160
[   35.313185]  [<ffffffff804768c5>] __mutex_unlock_slowpath+0xe5/0x190
[   35.313195]  [<ffffffff8026236a>] trace_hardirqs_on_caller+0xca/0x140
[   35.313205]  [<ffffffff8026ef4c>] sys_init_module+0xdc/0x210
[   35.313212]  [<ffffffff8020b7cb>] system_call_fastpath+0x16/0x1b

Signed-off-by: Andrea Righi <righi.andrea@...il.com>
---
 drivers/cpufreq/cpufreq_ondemand.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index aaa9e19..3098a94 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -638,8 +638,11 @@ static int __init cpufreq_gov_dbs_init(void)
 {
 	int err;
 	cputime64_t wall;
-	u64 idle_time = get_cpu_idle_time_us(smp_processor_id(), &wall);
+	u64 idle_time;
+	int cpu = get_cpu();
 
+	idle_time = get_cpu_idle_time_us(cpu, &wall);
+	put_cpu();
 	if (idle_time != -1ULL) {
 		/* Idle micro accounting is supported. Use finer thresholds */
 		dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
-- 
1.5.4.3
--
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