From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Linux PM list <linux-pm@vger.kernel.org>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: [Update][PATCH] PM / Hibernate: Fix s2disk regression related to unlock_system_sleep()
Date: Wed, 18 Jan 2012 00:15:56 +0100 [thread overview]
Message-ID: <201201180015.56510.rjw@sisk.pl> (raw)
In-Reply-To: <201201172345.15010.rjw@sisk.pl>
From: Rafael J. Wysocki <rjw@sisk.pl>
Subject: PM / Hibernate: Fix s2disk regression related to unlock_system_sleep()
Commit bcda53faf5814c0c6025a0bd47108adfcbe9f199, "PM / Sleep: Replace
mutex_[un]lock(&pm_mutex) with [un]lock_system_sleep()", modified
snapshot_read() and snapshot_write() in kernel/power/user.c, among
other things, by making them use lock_system_sleep() and
unlock_system_sleep() instead of just locking and unlocking pm_mutex.
Unfortunately, however, this was a mistake, because these routines
are supposed to be executed after processes have been frozen
(i.e. when system_freezing_cnt is nonzero), so when
unlock_system_sleep() is executed by one of them, this causes the
caller to execute try_to_freeze() and go into the refrigerator as
a result. This, in turn, deadlocks the suspend process and locks up
the system.
Fix the problem by reverting the part of commit bcda53faf5814c0c6025a
that changed snapshot_read() and snapshot_write().
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
Well, it wasn't a good idea to make snapshot_write() check
system_freezing_cnt, because the resume process doesn't freeze tasks.
So, it's better to simply revert the changes that introduced the
original regression.
Thanks,
Rafael
---
kernel/power/user.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
Index: linux/kernel/power/user.c
===================================================================
--- linux.orig/kernel/power/user.c
+++ linux/kernel/power/user.c
@@ -137,7 +137,7 @@ static ssize_t snapshot_read(struct file
ssize_t res;
loff_t pg_offp = *offp & ~PAGE_MASK;
- lock_system_sleep();
+ mutex_lock(&pm_mutex);
data = filp->private_data;
if (!data->ready) {
@@ -158,7 +158,7 @@ static ssize_t snapshot_read(struct file
*offp += res;
Unlock:
- unlock_system_sleep();
+ mutex_unlock(&pm_mutex);
return res;
}
@@ -170,7 +170,7 @@ static ssize_t snapshot_write(struct fil
ssize_t res;
loff_t pg_offp = *offp & ~PAGE_MASK;
- lock_system_sleep();
+ mutex_lock(&pm_mutex);
data = filp->private_data;
@@ -187,7 +187,7 @@ static ssize_t snapshot_write(struct fil
if (res > 0)
*offp += res;
unlock:
- unlock_system_sleep();
+ mutex_unlock(&pm_mutex);
return res;
}
next prev parent reply other threads:[~2012-01-17 23:12 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-17 22:45 [PATCH] PM / Hibernate: Fix s2disk regression related to unlock_system_sleep() Rafael J. Wysocki
2012-01-17 23:15 ` Rafael J. Wysocki [this message]
2012-01-18 12:59 ` [Update][PATCH] " Srivatsa S. Bhat
2012-01-18 15:42 ` Tejun Heo
2012-01-18 16:54 ` Srivatsa S. Bhat
2012-01-18 16:58 ` Tejun Heo
2012-01-18 17:19 ` Srivatsa S. Bhat
2012-01-18 17:30 ` Tejun Heo
2012-01-18 17:33 ` Tejun Heo
2012-01-19 10:37 ` Pavel Machek
2012-01-19 10:55 ` Srivatsa S. Bhat
2012-01-19 17:40 ` Pavel Machek
2012-01-19 18:10 ` Srivatsa S. Bhat
2012-01-18 19:22 ` Srivatsa S. Bhat
2012-01-18 19:30 ` Tejun Heo
2012-01-18 19:46 ` Srivatsa S. Bhat
2012-01-18 20:29 ` Srivatsa S. Bhat
2012-01-18 22:04 ` Tejun Heo
2012-01-18 22:22 ` Rafael J. Wysocki
2012-01-19 14:40 ` Srivatsa S. Bhat
2012-01-19 22:35 ` Rafael J. Wysocki
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