Re: [PATCH v2 1/2] cgroup/cpuset: reset DL migration state on can_attach() failure
From: Waiman Long
Date: Thu May 07 2026 - 22:26:52 EST
On 5/7/26 10:14 PM, Chen Ridong wrote:
Yes, that should work too.
On 2026/5/7 22:31, Waiman Long wrote:
On 5/7/26 6:33 AM, Guopeng Zhang wrote:I've read the code and found several places that call reset_migrate_dl_data(cs).
cpuset_can_attach() accumulates temporary SCHED_DEADLINE migrationI would prefer the likely success path be a straight line instead of doing a
state in the destination cpuset while walking the taskset.
If a later task_can_attach() or security_task_setscheduler() check
fails, cgroup_migrate_execute() treats cpuset as the failing subsystem
and does not call cpuset_cancel_attach() for it. The partially
accumulated state is then left behind and can be consumed by a later
attach, corrupting cpuset DL task accounting and pending DL bandwidth
accounting.
Reset the pending DL migration state before returning from those
per-task failure paths.
Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Signed-off-by: Guopeng Zhang <zhangguopeng@xxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index e3a081a07c6d..ae41736399a1 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3029,12 +3029,12 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
cgroup_taskset_for_each(task, css, tset) {
ret = task_can_attach(task);
if (ret)
- goto out_unlock;
+ goto out_reset_dl_data;
if (setsched_check) {
ret = security_task_setscheduler(task);
if (ret)
- goto out_unlock;
+ goto out_reset_dl_data;
}
if (dl_task(task)) {
@@ -3070,6 +3070,10 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
* changes which zero cpus/mems_allowed.
*/
cs->attach_in_progress++;
+ goto out_unlock;
+
+out_reset_dl_data:
+ reset_migrate_dl_data(cs);
out_unlock:
mutex_unlock(&cpuset_mutex);
return ret;
goto. IOW, move out_reset_dl_data below return. Other than that, this patch
looks good to me.
I think it would be better to call reset_migrate_dl_data(cs) only when we
encounter an error, for example:
```
static int cpuset_can_attach(struct cgroup_taskset *tset)
{
...
out_unlock:
if (ret)
reset_migrate_dl_data(cs);
mutex_unlock(&cpuset_mutex);
return ret;
}
```
After that, no other places would need to call reset_migrate_dl_data(cs), right?
Cheers,
Longman