Commit-ID: 23196f2e5f5d810578a772785807dcdc2b9fdce9 Gitweb: http://git.kernel.org/tip/23196f2e5f5d810578a772785807dcdc2b9fdce9 Author: Oleg Nesterov <o...@redhat.com> AuthorDate: Thu, 15 Sep 2016 22:45:44 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Fri, 16 Sep 2016 09:18:53 +0200
kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function 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.ga7...@redhat.com> Signed-off-by: Oleg Nesterov <o...@redhat.com> Signed-off-by: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Jann Horn <j...@thejh.net> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/cb9b16bbc19d4aea4507ab0552e4644c1211d130.1474003868.git.l...@kernel.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/kthread.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index 9ff173d..4ab4c37 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);
