Messages in this thread Patch in this message | | | From | "Srivatsa S. Bhat" <> | Subject | [PATCH v2] PM/Memory-hotplug: Avoid task freezing failures | Date | Wed, 16 Nov 2011 17:25:23 +0530 |
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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_trylock() in a loop until the lock is acquired, instead of using mutex_lock(), in order to avoid going to uninterruptible sleep. Also, try_to_freeze() is called within the loop, so that we don't cause freezing failures due to busy looping.
v2: Tejun pointed problems with using mutex_lock_interruptible() in a while loop, when signals not related to freezing are involved. So, replaced it with mutex_trylock().
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> ---
include/linux/suspend.h | 14 +++++++++++++- 1 files changed, 13 insertions(+), 1 deletions(-)
diff --git a/include/linux/suspend.h b/include/linux/suspend.h index 57a6924..c2b5aab 100644 --- a/include/linux/suspend.h +++ b/include/linux/suspend.h @@ -5,6 +5,7 @@ #include <linux/notifier.h> #include <linux/init.h> #include <linux/pm.h> +#include <linux/freezer.h> #include <linux/mm.h> #include <asm/errno.h> @@ -380,7 +381,18 @@ 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). + * + * We should use try_to_freeze() in the while loop so that we don't + * cause freezing failures due to busy looping. + */ + while (!mutex_trylock(&pm_mutex)) + try_to_freeze(); } static inline void unlock_system_sleep(void)
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