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| author | Oleg Nesterov <oleg@redhat.com> | 2016-11-14 19:46:12 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-11-22 12:33:43 +0100 |
| commit | 8e5bfa8c1f8471aa4a2d30be631ef2b50e10abaf (patch) | |
| tree | ad3d1c2dc3f1770ac865c8f1df91a53c1e276728 /kernel/sched | |
| parent | 18f649ef344127ef6de23a5a4272dbe2fdb73dde (diff) | |
| download | linux-stable-8e5bfa8c1f8471aa4a2d30be631ef2b50e10abaf.tar.gz linux-stable-8e5bfa8c1f8471aa4a2d30be631ef2b50e10abaf.tar.bz2 linux-stable-8e5bfa8c1f8471aa4a2d30be631ef2b50e10abaf.zip | |
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: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: hartsjc@redhat.com
Cc: vbendel@redhat.com
Cc: vlovejoy@redhat.com
Link: http://lkml.kernel.org/r/20161114184612.GA15968@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/auto_group.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c index ad2b19ad6ca0..f1c8fd566246 100644 --- a/kernel/sched/auto_group.c +++ b/kernel/sched/auto_group.c @@ -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(). + */ + sched_move_task(p); +} + 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) sched_move_task(t); |