Messages in this thread Patch in this message |  | | From | "Rafael J. Wysocki" <> | | Subject | [PATCH] PM / Hibernate: Fix s2disk regression related to unlock_system_sleep() | | Date | Tue, 17 Jan 2012 23:45:14 +0100 |
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From: Rafael J. Wysocki <rjw@sisk.pl>
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(). Additionally, make these functions check system_freezing_cnt and return error codes if it is zero to ensure that they won't do anything if tasks have not been frozen.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> --- kernel/power/user.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)
Index: linux/kernel/power/user.c =================================================================== --- linux.orig/kernel/power/user.c +++ linux/kernel/power/user.c @@ -137,7 +137,10 @@ static ssize_t snapshot_read(struct file ssize_t res; loff_t pg_offp = *offp & ~PAGE_MASK; - lock_system_sleep(); + if (!atomic_read(&system_freezing_cnt)) + return -EBUSY; + + mutex_lock(&pm_mutex); data = filp->private_data; if (!data->ready) { @@ -158,7 +161,7 @@ static ssize_t snapshot_read(struct file *offp += res; Unlock: - unlock_system_sleep(); + mutex_unlock(&pm_mutex); return res; } @@ -170,7 +173,10 @@ static ssize_t snapshot_write(struct fil ssize_t res; loff_t pg_offp = *offp & ~PAGE_MASK; - lock_system_sleep(); + if (!atomic_read(&system_freezing_cnt)) + return -EBUSY; + + mutex_lock(&pm_mutex); data = filp->private_data; @@ -187,7 +193,7 @@ static ssize_t snapshot_write(struct fil if (res > 0) *offp += res; unlock: - unlock_system_sleep(); + mutex_unlock(&pm_mutex); return res; }
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