From: Oleg Nesterov <oleg@xxxxxxxxxx>
get_task_struct(tsk) no longer pins tsk->stack so all users of
to_live_kthread() should do try_get_task_stack/put_task_stack to protect
"struct kthread" which lives on kthread's stack.
TODO: Kill to_live_kthread(), perhaps we can even kill "struct kthread" too,
and rework kthread_stop(), it can use task_work_add() to sync with the exiting
kernel thread.
Message-Id: <20160629180357.GA7178@xxxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
kernel/kthread.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 9ff173dca1ae..4ab4c3766a80 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -64,7 +64,7 @@ static inline struct kthread *to_kthread(struct task_struct *k)
static struct kthread *to_live_kthread(struct task_struct *k)
{
struct completion *vfork = ACCESS_ONCE(k->vfork_done);
- if (likely(vfork))
+ if (likely(vfork) && try_get_task_stack(k))
return __to_kthread(vfork);
return NULL;
}
@@ -425,8 +425,10 @@ void kthread_unpark(struct task_struct *k)
{
struct kthread *kthread = to_live_kthread(k);
- if (kthread)
+ if (kthread) {
__kthread_unpark(k, kthread);
+ put_task_stack(k);
+ }
}
EXPORT_SYMBOL_GPL(kthread_unpark);
@@ -455,6 +457,7 @@ int kthread_park(struct task_struct *k)
wait_for_completion(&kthread->parked);
}
}
+ put_task_stack(k);
ret = 0;
}
return ret;
@@ -490,6 +493,7 @@ int kthread_stop(struct task_struct *k)
__kthread_unpark(k, kthread);
wake_up_process(k);
wait_for_completion(&kthread->exited);
+ put_task_stack(k);
}
ret = k->exit_code;
put_task_struct(k);
--
2.7.4
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