From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965250Ab1KJQmy (ORCPT ); Thu, 10 Nov 2011 11:42:54 -0500 Received: from e28smtp01.in.ibm.com ([122.248.162.1]:52568 "EHLO e28smtp01.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935032Ab1KJQmw (ORCPT ); Thu, 10 Nov 2011 11:42:52 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH] PM/Memory-hotplug: Avoid task freezing failures To: rjw@sisk.pl Cc: pavel@ucw.cz, lenb@kernel.org, ak@linux.intel.com, tj@kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-mm@kvack.org Date: Thu, 10 Nov 2011 22:12:43 +0530 Message-ID: <20111110163825.4321.56320.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The lock_system_sleep() function is used in the memory hotplug code at several places in order to implement mutual exclusion with hibernation. However, this function tries to acquire the 'pm_mutex' lock using mutex_lock() and hence blocks in TASK_UNINTERRUPTIBLE state if it doesn't get the lock. This would lead to task freezing failures and hence hibernation failure as a consequence, even though the hibernation call path successfully acquired the lock. This patch fixes this issue by modifying lock_system_sleep() to use mutex_lock_interruptible() instead of mutex_lock(), so that it blocks in the TASK_INTERRUPTIBLE state. This would allow the freezer to freeze the blocked task. Also, since the freezer could use signals to freeze tasks, it is quite likely that mutex_lock_interruptible() returns -EINTR (and fails to acquire the lock). Hence we keep retrying in a loop until we acquire the lock. Also, we call try_to_freeze() within the loop, so that we don't cause freezing failures due to busy looping. Signed-off-by: Srivatsa S. Bhat --- include/linux/suspend.h | 18 +++++++++++++++++- 1 files changed, 17 insertions(+), 1 deletions(-) diff --git a/include/linux/suspend.h b/include/linux/suspend.h index 57a6924..02a0d09 100644 --- a/include/linux/suspend.h +++ b/include/linux/suspend.h @@ -5,6 +5,7 @@ #include #include #include +#include #include #include @@ -380,7 +381,22 @@ static inline void unlock_system_sleep(void) {} static inline void lock_system_sleep(void) { - mutex_lock(&pm_mutex); + /* + * We should not use mutex_lock() here because, in case we fail to + * acquire the lock, it would put us to sleep in TASK_UNINTERRUPTIBLE + * state, which would lead to task freezing failures. As a + * consequence, hibernation would fail (even though it had acquired + * the 'pm_mutex' lock). + * + * Note that mutex_lock_interruptible() returns -EINTR if we happen + * to get a signal when we are waiting to acquire the lock (and this + * is very likely here because the freezer could use signals to freeze + * tasks). Hence we have to keep retrying until we get the lock. But + * we have to use try_to_freeze() in the loop, so that we don't cause + * freezing failures due to busy looping. + */ + while (mutex_lock_interruptible(&pm_mutex)) + try_to_freeze(); } static inline void unlock_system_sleep(void)