Commit 8e5bfa8c authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar

sched/autogroup: Do not use autogroup->tg in zombie threads

Exactly because for_each_thread() in autogroup_move_group() can't see it
and update its ->sched_task_group before _put() and possibly free().

So the exiting task needs another sched_move_task() before exit_notify()
and we need to re-introduce the PF_EXITING (or similar) check removed by
the previous change for another reason.
Signed-off-by: default avatarOleg Nesterov <>
Signed-off-by: default avatarPeter Zijlstra (Intel) <>
Cc: Linus Torvalds <>
Cc: Mike Galbraith <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Link: default avatarIngo Molnar <>
parent 18f649ef
......@@ -2567,6 +2567,7 @@ extern void sched_autogroup_create_attach(struct task_struct *p);
extern void sched_autogroup_detach(struct task_struct *p);
extern void sched_autogroup_fork(struct signal_struct *sig);
extern void sched_autogroup_exit(struct signal_struct *sig);
extern void sched_autogroup_exit_task(struct task_struct *p);
extern void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m);
extern int proc_sched_autogroup_set_nice(struct task_struct *p, int nice);
......@@ -2576,6 +2577,7 @@ static inline void sched_autogroup_create_attach(struct task_struct *p) { }
static inline void sched_autogroup_detach(struct task_struct *p) { }
static inline void sched_autogroup_fork(struct signal_struct *sig) { }
static inline void sched_autogroup_exit(struct signal_struct *sig) { }
static inline void sched_autogroup_exit_task(struct task_struct *p) { }
extern int yield_to(struct task_struct *p, bool preempt);
......@@ -836,6 +836,7 @@ void __noreturn do_exit(long code)
......@@ -115,10 +115,26 @@ bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
* If we race with autogroup_move_group() the caller can use the old
* value of signal->autogroup but in this case sched_move_task() will
* be called again before autogroup_kref_put().
* However, there is no way sched_autogroup_exit_task() could tell us
* to avoid autogroup->tg, so we abuse PF_EXITING flag for this case.
if (p->flags & PF_EXITING)
return false;
return true;
void sched_autogroup_exit_task(struct task_struct *p)
* We are going to call exit_notify() and autogroup_move_group() can't
* see this thread after that: we can no longer use signal->autogroup.
* See the PF_EXITING check in task_wants_autogroup().
static void
autogroup_move_group(struct task_struct *p, struct autogroup *ag)
......@@ -142,6 +158,9 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag)
* In the latter case for_each_thread() can not miss a migrating thread,
* cpu_cgroup_attach() must not be possible after cgroup_exit() and it
* can't be removed from thread list, we hold ->siglock.
* If an exiting thread was already removed from thread list we rely on
* sched_autogroup_exit_task().
for_each_thread(p, t)
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