| From 4f20a35ad56f5ee15bbcc4e14966960647931940 Mon Sep 17 00:00:00 2001 |
| From: Oleg Nesterov <oleg@redhat.com> |
| Date: Thu, 15 Sep 2016 22:45:44 -0700 |
| Subject: [PATCH] kthread: Pin the stack via |
| try_get_task_stack()/put_task_stack() in to_live_kthread() function |
| |
| commit 23196f2e5f5d810578a772785807dcdc2b9fdce9 upstream. |
| |
| 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@redhat.com> |
| Signed-off-by: Oleg Nesterov <oleg@redhat.com> |
| Signed-off-by: Andy Lutomirski <luto@kernel.org> |
| Cc: Borislav Petkov <bp@alien8.de> |
| Cc: Brian Gerst <brgerst@gmail.com> |
| Cc: Denys Vlasenko <dvlasenk@redhat.com> |
| Cc: H. Peter Anvin <hpa@zytor.com> |
| Cc: Jann Horn <jann@thejh.net> |
| Cc: Josh Poimboeuf <jpoimboe@redhat.com> |
| Cc: Linus Torvalds <torvalds@linux-foundation.org> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Link: http://lkml.kernel.org/r/cb9b16bbc19d4aea4507ab0552e4644c1211d130.1474003868.git.luto@kernel.org |
| Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| |
| diff --git a/kernel/kthread.c b/kernel/kthread.c |
| index 850b255649a2..d982c65f1578 100644 |
| --- a/kernel/kthread.c |
| +++ b/kernel/kthread.c |
| @@ -65,7 +65,7 @@ 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; |
| } |
| @@ -427,8 +427,10 @@ 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); |
| |
| @@ -457,6 +459,7 @@ int kthread_park(struct task_struct *k) |
| wait_for_completion(&kthread->parked); |
| } |
| } |
| + put_task_stack(k); |
| ret = 0; |
| } |
| return ret; |
| @@ -492,6 +495,7 @@ 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); |
| -- |
| 2.15.0 |
| |