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authorSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>2011-11-22 02:32:35 +0400
committerRafael J. Wysocki <rjw@sisk.pl>2011-11-24 00:13:16 +0400
commit6a76b7a9cc93dec6ae58d70f1257d234291908e0 (patch)
tree4f9d44d2643b96f7ec7245734ef869bd2b1a3600
parent341d4166175e9b7911444f5a33b1c9efb8f15c85 (diff)
downloadlinux-6a76b7a9cc93dec6ae58d70f1257d234291908e0.tar.xz
PM / Memory-hotplug: Avoid task freezing failures
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. But it is to be noted that, since this task tries to acquire pm_mutex, if it blocks due to this, we are *100% sure* that this task is not going to run as long as hibernation sequence is in progress, since hibernation releases 'pm_mutex' only at the very end, when everything is done. And this means, this task is going to be anyway blocked for much more longer than what the freezer intends to achieve; which means, freezing and thawing doesn't really make any difference to this task! So, to fix freezing failures, we just ask the freezer to skip freezing this task, since it is already "frozen enough". But instead of calling freezer_do_not_count() and freezer_count() as it is, we use only the relevant parts of those functions, because restrictions such as 'the task should be a userspace one' etc., might not be relevant in this scenario. Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
-rw-r--r--include/linux/suspend.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 57a692432f8a..1f7fff47cfac 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -380,12 +380,16 @@ static inline void unlock_system_sleep(void) {}
static inline void lock_system_sleep(void)
{
+ /* simplified freezer_do_not_count() */
+ current->flags |= PF_FREEZER_SKIP;
mutex_lock(&pm_mutex);
}
static inline void unlock_system_sleep(void)
{
mutex_unlock(&pm_mutex);
+ /* simplified freezer_count() */
+ current->flags &= ~PF_FREEZER_SKIP;
}
#endif