From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Andi Kleen" Subject: [PATCH] [7/7] x86_64: Move ondemand timer into own work queue Date: Fri, 05 May 2006 20:33:14 +0200 Message-ID: <445B9A6A.mailIZ41BYSAC@suse.de> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: cpufreq-bounces@lists.linux.org.uk Errors-To: cpufreq-bounces+glkc-cpufreq=m.gmane.org+glkc-cpufreq=m.gmane.org@lists.linux.org.uk Content-Type: text/plain; charset="us-ascii" To: torvalds@osdl.org Cc: akpm@osdl.org, discuss@x86-64.org, cpufreq@lists.linux.org.uk Taking the cpu hotplug semaphore in a normal events workqueue is unsafe because other tasks can wait for any workqueues with it hold. This results in a deadlock. Move the DBS timer into its own work queue which is not affected by other work queue flushes to avoid this. Cc: venkatesh.pallipadi@intel.com Cc: cpufreq@lists.linux.org.uk Signed-off-by: Andi Kleen --- drivers/cpufreq/cpufreq_ondemand.c | 28 ++++++++++++++++++++-------- 1 files changed, 20 insertions(+), 8 deletions(-) Index: linux/drivers/cpufreq/cpufreq_ondemand.c =================================================================== --- linux.orig/drivers/cpufreq/cpufreq_ondemand.c +++ linux/drivers/cpufreq/cpufreq_ondemand.c @@ -74,6 +74,8 @@ static unsigned int dbs_enable; /* numbe static DEFINE_MUTEX (dbs_mutex); static DECLARE_WORK (dbs_work, do_dbs_timer, NULL); +static struct workqueue_struct *dbs_workq; + struct dbs_tuners { unsigned int sampling_rate; unsigned int sampling_down_factor; @@ -364,23 +366,29 @@ static void do_dbs_timer(void *data) mutex_lock(&dbs_mutex); for_each_online_cpu(i) dbs_check_cpu(i); - schedule_delayed_work(&dbs_work, - usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); + queue_delayed_work(dbs_workq, &dbs_work, + usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); mutex_unlock(&dbs_mutex); } static inline void dbs_timer_init(void) { INIT_WORK(&dbs_work, do_dbs_timer, NULL); - schedule_delayed_work(&dbs_work, - usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); + if (!dbs_workq) + dbs_workq = create_singlethread_workqueue("ondemand"); + if (!dbs_workq) { + printk(KERN_ERR "ondemand: Cannot initialize kernel thread\n"); + return; + } + queue_delayed_work(dbs_workq, &dbs_work, + usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); return; } static inline void dbs_timer_exit(void) { - cancel_delayed_work(&dbs_work); - return; + if (dbs_workq) + cancel_rearming_delayed_workqueue(dbs_workq, &dbs_work); } static int cpufreq_governor_dbs(struct cpufreq_policy *policy, @@ -489,8 +497,12 @@ static int __init cpufreq_gov_dbs_init(v static void __exit cpufreq_gov_dbs_exit(void) { - /* Make sure that the scheduled work is indeed not running */ - flush_scheduled_work(); + /* Make sure that the scheduled work is indeed not running. + Assumes the timer has been cancelled first. */ + if (dbs_workq) { + flush_workqueue(dbs_workq); + destroy_workqueue(dbs_workq); + } cpufreq_unregister_governor(&cpufreq_gov_dbs); }