Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754723AbXHAVbw (ORCPT ); Wed, 1 Aug 2007 17:31:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752660AbXHAVbH (ORCPT ); Wed, 1 Aug 2007 17:31:07 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:37192 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751795AbXHAVbC convert rfc822-to-8bit (ORCPT ); Wed, 1 Aug 2007 17:31:02 -0400 From: "Rafael J. Wysocki" To: Andrew Morton Subject: [PATCH -mm 2/3] Freezer: Use wait queue instead of busy looping Date: Wed, 1 Aug 2007 23:32:48 +0200 User-Agent: KMail/1.9.5 Cc: LKML , Nigel Cunningham , Oleg Nesterov , Pavel Machek , pm list References: <200708012328.23939.rjw@sisk.pl> In-Reply-To: <200708012328.23939.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: 8BIT Content-Disposition: inline Message-Id: <200708012332.48798.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3026 Lines: 99 From: Rafael J. Wysocki Use the observation that try_to_freeze_tasks() need not loop while waiting for the freezing tasks to enter the refrigerator and make it use a wait queue. The idea is that after sending freeze requests to the tasks regarded as freezable try_to_freeze_tasks() can go to sleep and wait until at least one task enters the refrigerator. ?The first task that does it wakes up try_to_freeze_tasks() and the procedure is repeated. ?If the refrigerator is not entered by any tasks before TIMEOUT expires, the freezing of tasks fails. This way, try_to_freeze_tasks() doesn't occupy the CPU unnecessarily when some freezing tasks are waiting for I/O to complete. Signed-off-by: Rafael J. Wysocki Acked-by: Pavel Machek --- kernel/power/process.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) Index: linux-2.6.23-rc1/kernel/power/process.c =================================================================== --- linux-2.6.23-rc1.orig/kernel/power/process.c 2007-07-31 21:58:32.000000000 +0200 +++ linux-2.6.23-rc1/kernel/power/process.c 2007-07-31 23:00:43.000000000 +0200 @@ -19,6 +19,12 @@ */ #define TIMEOUT (20 * HZ) +/* + * Time to wait until one or more tasks enter the refrigerator after sending + * freeze requests to them. + */ +#define WAIT_TIME (HZ / 5) + #define FREEZER_KERNEL_THREADS 0 #define FREEZER_USER_SPACE 1 @@ -43,6 +49,18 @@ static inline void frozen_process(void) clear_freeze_flag(current); } +/* + * Wait queue head used by try_to_freeze_tasks() to wait for tasks to enter the + * refrigerator. + */ +static DECLARE_WAIT_QUEUE_HEAD(refrigerator_waitq); + +/* + * Used to notify try_to_freeze_tasks() that the refrigerator has been entered + * by a task. + */ +static int refrigerator_called; + /* Refrigerator is place where frozen processes are stored :-). */ void refrigerator(void) { @@ -58,6 +76,10 @@ void refrigerator(void) task_unlock(current); return; } + + refrigerator_called = 1; + wake_up(&refrigerator_waitq); + save = current->state; pr_debug("%s entered refrigerator\n", current->comm); @@ -170,6 +192,7 @@ static int try_to_freeze_tasks(int freez unsigned int todo; end_time = jiffies + TIMEOUT; + refrigerator_called = 0; do { todo = 0; read_lock(&tasklist_lock); @@ -189,7 +212,16 @@ static int try_to_freeze_tasks(int freez todo++; } while_each_thread(g, p); read_unlock(&tasklist_lock); - yield(); /* Yield is okay here */ + + if (todo) { + unsigned long ret; + + ret = wait_event_timeout(refrigerator_waitq, + refrigerator_called, WAIT_TIME); + if (ret) + refrigerator_called = 0; + } + if (time_after(jiffies, end_time)) break; } while (todo); - 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/