Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756772Ab2JITiy (ORCPT ); Tue, 9 Oct 2012 15:38:54 -0400 Received: from ch1ehsobe004.messaging.microsoft.com ([216.32.181.184]:43678 "EHLO ch1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752760Ab2JITiv (ORCPT ); Tue, 9 Oct 2012 15:38:51 -0400 X-Forefront-Antispam-Report: CIP:163.181.249.108;KIP:(null);UIP:(null);IPV:NLI;H:ausb3twp01.amd.com;RD:none;EFVD:NLI X-SpamScore: 0 X-BigFish: VPS0(zzzz1202h1d1ah1d2ahzz8275bh8275dhz2dh668h839h93fhd25hd2bhf0ah107ah1288h12a5h12a9h12bdh137ah13b6h1441h1155h) X-WSS-ID: 0MBN58L-01-0FZ-02 X-M-MSG: Date: Tue, 9 Oct 2012 21:38:44 +0200 From: Andreas Herrmann To: "Rafael J. Wysocki" CC: , , Tejun Heo , Subject: [PATCH] cpufreq, powernow-k8: Fix usage of smp_processor_id() in preemptible code Message-ID: <20121009193844.GC7724@alberich> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-OriginatorOrg: amd.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2730 Lines: 75 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/