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kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function

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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>
This commit is contained in:
Oleg Nesterov 2016-09-15 22:45:44 -07:00 committed by Ingo Molnar
parent c6c314a613
commit 23196f2e5f
1 changed files with 6 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

8
kernel/kthread.c
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@ -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);