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authorRafael J. Wysocki <rjw@sisk.pl>2007-05-23 13:57:24 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-23 20:14:10 -0700
commit33e1c288da62a6a5aa9077a6b7bfa690b1b02cf4 (patch)
tree68837483316db1fa08bcb2b444cabae75d31a5b2 /kernel/power
parent585a2858b970cb6e2e5ca4877eefd18b4dba8ed4 (diff)
freezer: close potential race between refrigerator and thaw_tasks
If the freezing of tasks fails and a task is preempted in refrigerator() before calling frozen_process(), then thaw_tasks() may run before this task is frozen. In that case the task will freeze and no one will thaw it. To fix this race we can call freezing(current) in refrigerator() along with frozen_process(current) under the task_lock() which also should be taken in the error path of try_to_freeze_tasks() as well as in thaw_process(). Moreover, if thaw_process() additionally clears TIF_FREEZE for tasks that are not frozen, we can be sure that all tasks are thawed and there are no pending "freeze" requests after thaw_tasks() has run. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Pavel Machek <pavel@ucw.cz> Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/power')
-rw-r--r--kernel/power/process.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 088419387388..02e490e311eb 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -37,10 +37,18 @@ void refrigerator(void)
/* Hmm, should we be allowed to suspend when there are realtime
processes around? */
long save;
+
+ task_lock(current);
+ if (freezing(current)) {
+ frozen_process(current);
+ task_unlock(current);
+ } else {
+ task_unlock(current);
+ return;
+ }
save = current->state;
pr_debug("%s entered refrigerator\n", current->comm);
- frozen_process(current);
spin_lock_irq(&current->sighand->siglock);
recalc_sigpending(); /* We sent fake signal, clean it up */
spin_unlock_irq(&current->sighand->siglock);
@@ -152,10 +160,12 @@ static unsigned int try_to_freeze_tasks(int freeze_user_space)
if (is_user_space(p) == !freeze_user_space)
continue;
+ task_lock(p);
if (freezeable(p) && !frozen(p))
printk(KERN_ERR " %s\n", p->comm);
cancel_freezing(p);
+ task_unlock(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
}