From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Herrmann Subject: [PATCH] cpufreq, powernow-k8: Fix usage of smp_processor_id() in preemptible code Date: Tue, 9 Oct 2012 21:38:44 +0200 Message-ID: <20121009193844.GC7724@alberich> Mime-Version: 1.0 Return-path: Content-Disposition: inline Sender: cpufreq-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Rafael J. Wysocki" Cc: linux-kernel@vger.kernel.org, cpufreq@vger.kernel.org, Tejun Heo , stable@vger.kernel.org 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: [] debug_smp_processor_id+0xc7/0xe0 [] powernowk8_target+0x20/0x49 [] __cpufreq_driver_target+0x82/0x8a [] cpufreq_governor_performance+0x4e/0x54 [] __cpufreq_governor+0x8c/0xc9 [] __cpufreq_set_policy+0x1a9/0x21e [] store_scaling_governor+0x16f/0x19b [] ? cpufreq_update_policy+0x124/0x124 [] ? _raw_spin_unlock_irqrestore+0x2c/0x49 [] store+0x60/0x88 [] sysfs_write_file+0xf4/0x130 [] vfs_write+0xb5/0x151 [] sys_write+0x4a/0x71 [] system_call_fastpath+0x16/0x1b Fix this by using get_cpu/put_cpu in powernowk8_target(). Cc: Tejun Heo Cc: stable@vger.kernel.org Signed-off-by: Andreas Herrmann --- drivers/cpufreq/powernow-k8.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c index 1a40935..3d1df2a 100644 --- a/drivers/cpufreq/powernow-k8.c +++ b/drivers/cpufreq/powernow-k8.c @@ -1220,17 +1220,20 @@ static long powernowk8_target_fn(void *arg) static int powernowk8_target(struct cpufreq_policy *pol, unsigned targfreq, unsigned relation) { + int this_cpu, ret; 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); + this_cpu = get_cpu(); + if (this_cpu == pol->cpu) { + ret = powernowk8_target_fn(&pta); + put_cpu(); + } else { + put_cpu(); + ret = work_on_cpu(pol->cpu, powernowk8_target_fn, &pta); + } + + return ret; } /* Driver entry point to verify the policy and range of frequencies */ -- 1.7.12