[PATCH v3] freezer, sched: report the frozen task stat as 'D'

[PATCH v3] freezer, sched: report the frozen task stat as 'D'

[Chen Ridong]

From: Chen Ridong <chenridong@huawei.com>

Before the commit f5d39b020809 ("freezer,sched: Rewrite core freezer
logic"), the frozen task stat was reported as 'D' in cgroup v1.
However, after rewriting core freezer logic, the frozen task stat is
reported as 'R'. This is confusing, especially when a task with stat of
'S' is frozen.

This can be reproduced as bellow step:
cd /sys/fs/cgroup/freezer/
mkdir test
sleep 1000 &
[1] 739         // task whose stat is 'S'
echo 739 > test/cgroup.procs
echo FROZEN > test/freezer.state
ps -aux | grep 739
root     739  0.1  0.0   8376  1812 pts/0    R    10:56   0:00 sleep 1000

As shown above, a task whose stat is 'S' was changed to 'R' when it was
frozen. To solve this issue, simply maintain the same reported state as
before the rewrite.

Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
---
 include/linux/sched.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index d380bffee2ef..fdcb7c75386c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1630,8 +1630,9 @@ static inline unsigned int __task_state_index(unsigned int tsk_state,
 	 * We're lying here, but rather than expose a completely new task state
 	 * to userspace, we can make this appear as if the task has gone through
 	 * a regular rt_mutex_lock() call.
+	 * Report the frozen task uninterruptible.
 	 */
-	if (tsk_state & TASK_RTLOCK_WAIT)
+	if ((tsk_state & TASK_RTLOCK_WAIT) || (tsk_state & TASK_FROZEN))
 		state = TASK_UNINTERRUPTIBLE;
 
 	return fls(state);
-- 
2.34.1

Re: [PATCH v3] freezer, sched: report the frozen task stat as 'D'

[Michal Koutný]

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On Tue, Dec 17, 2024 at 12:48:18AM GMT, Chen Ridong <chenridong@huaweicloud.com> wrote:
>  include/linux/sched.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Acked-by: Michal Koutný <mkoutny@suse.com>

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Re: [PATCH v3] freezer, sched: report the frozen task stat as 'D'

[Peter Zijlstra]

On Tue, Dec 17, 2024 at 12:48:18AM +0000, Chen Ridong wrote:
> From: Chen Ridong <chenridong@huawei.com>
> 
> Before the commit f5d39b020809 ("freezer,sched: Rewrite core freezer
> logic"), the frozen task stat was reported as 'D' in cgroup v1.
> However, after rewriting core freezer logic, the frozen task stat is
> reported as 'R'. This is confusing, especially when a task with stat of
> 'S' is frozen.
> 
> This can be reproduced as bellow step:
> cd /sys/fs/cgroup/freezer/
> mkdir test
> sleep 1000 &
> [1] 739         // task whose stat is 'S'
> echo 739 > test/cgroup.procs
> echo FROZEN > test/freezer.state
> ps -aux | grep 739
> root     739  0.1  0.0   8376  1812 pts/0    R    10:56   0:00 sleep 1000
> 
> As shown above, a task whose stat is 'S' was changed to 'R' when it was
> frozen. To solve this issue, simply maintain the same reported state as
> before the rewrite.
> 
> Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> Acked-by: Tejun Heo <tj@kernel.org>

Thanks!

Re: [PATCH v3] freezer, sched: report the frozen task stat as 'D'

[Roman Gushchin]

On Tue, Dec 17, 2024 at 12:48:18AM +0000, Chen Ridong wrote:
> From: Chen Ridong <chenridong@huawei.com>
> 
> Before the commit f5d39b020809 ("freezer,sched: Rewrite core freezer
> logic"), the frozen task stat was reported as 'D' in cgroup v1.
> However, after rewriting core freezer logic, the frozen task stat is
> reported as 'R'. This is confusing, especially when a task with stat of
> 'S' is frozen.
> 
> This can be reproduced as bellow step:
> cd /sys/fs/cgroup/freezer/
> mkdir test
> sleep 1000 &
> [1] 739         // task whose stat is 'S'
> echo 739 > test/cgroup.procs
> echo FROZEN > test/freezer.state
> ps -aux | grep 739
> root     739  0.1  0.0   8376  1812 pts/0    R    10:56   0:00 sleep 1000
> 
> As shown above, a task whose stat is 'S' was changed to 'R' when it was
> frozen. To solve this issue, simply maintain the same reported state as
> before the rewrite.
> 
> Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> Acked-by: Tejun Heo <tj@kernel.org>

Acked-by: Roman Gushchin <roman.gushchin@linux.dev>

Thank you!

[tip: sched/urgent] freezer, sched: report the frozen task stat as 'D'

[tip-bot2 for Chen Ridong]

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     2357a7f934ae01985b0b8b70c3ca59ea38b9ed5b
Gitweb:        https://git.kernel.org/tip/2357a7f934ae01985b0b8b70c3ca59ea38b9ed5b
Author:        Chen Ridong <chenridong@huawei.com>
AuthorDate:    Tue, 17 Dec 2024 00:48:18 
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 17 Dec 2024 17:47:20 +01:00

freezer, sched: report the frozen task stat as 'D'

Before the commit f5d39b020809 ("freezer,sched: Rewrite core freezer
logic"), the frozen task stat was reported as 'D' in cgroup v1.
However, after rewriting core freezer logic, the frozen task stat is
reported as 'R'. This is confusing, especially when a task with stat of
'S' is frozen.

This can be reproduced as bellow step:
cd /sys/fs/cgroup/freezer/
mkdir test
sleep 1000 &
[1] 739         // task whose stat is 'S'
echo 739 > test/cgroup.procs
echo FROZEN > test/freezer.state
ps -aux | grep 739
root     739  0.1  0.0   8376  1812 pts/0    R    10:56   0:00 sleep 1000

As shown above, a task whose stat is 'S' was changed to 'R' when it was
frozen. To solve this issue, simply maintain the same reported state as
before the rewrite.

Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Koutný <mkoutny@suse.com>
Link: https://lore.kernel.org/r/20241217004818.3200515-1-chenridong@huaweicloud.com
---
 include/linux/sched.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 66b311f..6c98649 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1637,8 +1637,9 @@ static inline unsigned int __task_state_index(unsigned int tsk_state,
 	 * We're lying here, but rather than expose a completely new task state
 	 * to userspace, we can make this appear as if the task has gone through
 	 * a regular rt_mutex_lock() call.
+	 * Report the frozen task uninterruptible.
 	 */
-	if (tsk_state & TASK_RTLOCK_WAIT)
+	if ((tsk_state & TASK_RTLOCK_WAIT) || (tsk_state & TASK_FROZEN))
 		state = TASK_UNINTERRUPTIBLE;
 
 	return fls(state);

[tip: sched/urgent] freezer, sched: Report frozen tasks as 'D' instead of 'R'

[tip-bot2 for Chen Ridong]

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     f718faf3940e95d5d34af9041f279f598396ab7d
Gitweb:        https://git.kernel.org/tip/f718faf3940e95d5d34af9041f279f598396ab7d
Author:        Chen Ridong <chenridong@huawei.com>
AuthorDate:    Tue, 17 Dec 2024 00:48:18 
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sun, 29 Dec 2024 10:14:20 +01:00

freezer, sched: Report frozen tasks as 'D' instead of 'R'

Before commit:

  f5d39b020809 ("freezer,sched: Rewrite core freezer logic")

the frozen task stat was reported as 'D' in cgroup v1.

However, after rewriting the core freezer logic, the frozen task stat is
reported as 'R'. This is confusing, especially when a task with stat of
'S' is frozen.

This bug can be reproduced with these steps:

	$ cd /sys/fs/cgroup/freezer/
	$ mkdir test
	$ sleep 1000 &
	[1] 739         // task whose stat is 'S'
	$ echo 739 > test/cgroup.procs
	$ echo FROZEN > test/freezer.state
	$ ps -aux | grep 739
	root     739  0.1  0.0   8376  1812 pts/0    R    10:56   0:00 sleep 1000

As shown above, a task whose stat is 'S' was changed to 'R' when it was
frozen.

To solve this regression, simply maintain the same reported state as
before the rewrite.

[ mingo: Enhanced the changelog and comments ]

Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Koutný <mkoutny@suse.com>
Link: https://lore.kernel.org/r/20241217004818.3200515-1-chenridong@huaweicloud.com
---
 include/linux/sched.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 66b311f..64934e0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1637,8 +1637,9 @@ static inline unsigned int __task_state_index(unsigned int tsk_state,
 	 * We're lying here, but rather than expose a completely new task state
 	 * to userspace, we can make this appear as if the task has gone through
 	 * a regular rt_mutex_lock() call.
+	 * Report frozen tasks as uninterruptible.
 	 */
-	if (tsk_state & TASK_RTLOCK_WAIT)
+	if ((tsk_state & TASK_RTLOCK_WAIT) || (tsk_state & TASK_FROZEN))
 		state = TASK_UNINTERRUPTIBLE;
 
 	return fls(state);