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| author | Chen Ridong <chenridong@huawei.com> | 2025-07-17 08:55:49 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-07-24 08:58:43 +0200 |
| commit | cfbc462192aa4104900a2e1a67b116ea9e7075b6 (patch) | |
| tree | 20d8d873a76637e056cd02b6201ef54a8ede91d4 /kernel | |
| parent | dceebcfeaa286c2a46e2b97faba065498b423c97 (diff) | |
| download | linux-cfbc462192aa4104900a2e1a67b116ea9e7075b6.tar.gz linux-cfbc462192aa4104900a2e1a67b116ea9e7075b6.tar.bz2 linux-cfbc462192aa4104900a2e1a67b116ea9e7075b6.zip | |
sched,freezer: Remove unnecessary warning in __thaw_task
commit 9beb8c5e77dc10e3889ff5f967eeffba78617a88 upstream.
Commit cff5f49d433f ("cgroup_freezer: cgroup_freezing: Check if not
frozen") modified the cgroup_freezing() logic to verify that the FROZEN
flag is not set, affecting the return value of the freezing() function,
in order to address a warning in __thaw_task.
A race condition exists that may allow tasks to escape being frozen. The
following scenario demonstrates this issue:
CPU 0 (get_signal path) CPU 1 (freezer.state reader)
try_to_freeze read freezer.state
__refrigerator freezer_read
update_if_frozen
WRITE_ONCE(current->__state, TASK_FROZEN);
...
/* Task is now marked frozen */
/* frozen(task) == true */
/* Assuming other tasks are frozen */
freezer->state |= CGROUP_FROZEN;
/* freezing(current) returns false */
/* because cgroup is frozen (not freezing) */
break out
__set_current_state(TASK_RUNNING);
/* Bug: Task resumes running when it should remain frozen */
The existing !frozen(p) check in __thaw_task makes the
WARN_ON_ONCE(freezing(p)) warning redundant. Removing this warning enables
reverting commit cff5f49d433f ("cgroup_freezer: cgroup_freezing: Check if
not frozen") to resolve the issue.
This patch removes the warning from __thaw_task. A subsequent patch will
revert commit cff5f49d433f ("cgroup_freezer: cgroup_freezing: Check if
not frozen") to complete the fix.
Reported-by: Zhong Jiawei<zhongjiawei1@huawei.com>
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/freezer.c | 15 |
1 files changed, 3 insertions, 12 deletions
diff --git a/kernel/freezer.c b/kernel/freezer.c index 8d530d0949ff..6a96149aede9 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -201,18 +201,9 @@ static int __restore_freezer_state(struct task_struct *p, void *arg) void __thaw_task(struct task_struct *p) { - unsigned long flags; - - spin_lock_irqsave(&freezer_lock, flags); - if (WARN_ON_ONCE(freezing(p))) - goto unlock; - - if (!frozen(p) || task_call_func(p, __restore_freezer_state, NULL)) - goto unlock; - - wake_up_state(p, TASK_FROZEN); -unlock: - spin_unlock_irqrestore(&freezer_lock, flags); + guard(spinlock_irqsave)(&freezer_lock); + if (frozen(p) && !task_call_func(p, __restore_freezer_state, NULL)) + wake_up_state(p, TASK_FROZEN); } /** |