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Groups > linux.kernel > #1433941
| From | Oleg Nesterov <oleg@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH] kthread: to_live_kthread() needs try_get_task_stack() |
| Date | 2016-06-29 20:10 +0200 |
| Message-ID | <rPs5Z-7vv-55@gated-at.bofh.it> (permalink) |
| References | (5 earlier) <rP6I9-2Di-7@gated-at.bofh.it> <rP7Ee-3d8-45@gated-at.bofh.it> <rP8gW-3r9-31@gated-at.bofh.it> <rPaiJ-4Rk-9@gated-at.bofh.it> <rPpKO-5V4-29@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 06/29, Andy Lutomirski wrote:
>
> I pushed that change to my tree (seems to work well enough to boot
> without warnings as long as I don't unmount XFS, but not particularly
> well tested). Want to refresh your patch on top?
Please see the trivial fix below. Compile tested, but looks obvious.
Btw, why free_thread_stack() calls vfree() with irqs disabled? Doesn't
look good and perhaps even wrong; at least vmap_debug_free_range() does
flush_tlb_kernel_range() and smp_call_function() can deadlock?
-------------------------------------------------------------------------------
Subject: [PATCH] kthread: to_live_kthread() needs try_get_task_stack()
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.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
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);
--
2.5.0
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kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Andy Lutomirski <luto@kernel.org> - 2016-06-27 07:30 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Peter Zijlstra <peterz@infradead.org> - 2016-06-27 10:30 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Oleg Nesterov <oleg@redhat.com> - 2016-06-27 17:00 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Andy Lutomirski <luto@amacapital.net> - 2016-06-27 17:50 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Oleg Nesterov <oleg@redhat.com> - 2016-06-27 19:00 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Oleg Nesterov <oleg@redhat.com> - 2016-06-28 21:00 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Andy Lutomirski <luto@amacapital.net> - 2016-06-28 21:20 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Oleg Nesterov <oleg@redhat.com> - 2016-06-28 22:20 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Andy Lutomirski <luto@amacapital.net> - 2016-06-28 23:00 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-28 23:20 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-28 23:20 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Andy Lutomirski <luto@amacapital.net> - 2016-06-28 23:30 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-28 23:40 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-28 23:50 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Oleg Nesterov <oleg@redhat.com> - 2016-06-29 01:00 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Oleg Nesterov <oleg@redhat.com> - 2016-06-29 01:10 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Andy Lutomirski <luto@amacapital.net> - 2016-06-29 17:40 +0200
[PATCH] kthread: to_live_kthread() needs try_get_task_stack() Oleg Nesterov <oleg@redhat.com> - 2016-06-29 20:10 +0200
Re: [PATCH] kthread: to_live_kthread() needs try_get_task_stack() kbuild test robot <lkp@intel.com> - 2016-06-29 20:40 +0200
Re: [PATCH] kthread: to_live_kthread() needs try_get_task_stack() Oleg Nesterov <oleg@redhat.com> - 2016-06-29 20:50 +0200
Re: [PATCH] kthread: to_live_kthread() needs try_get_task_stack() kbuild test robot <lkp@intel.com> - 2016-06-29 21:00 +0200
Re: [PATCH] kthread: to_live_kthread() needs try_get_task_stack() Andy Lutomirski <luto@amacapital.net> - 2016-06-30 01:10 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Andy Lutomirski <luto@amacapital.net> - 2016-06-30 01:40 +0200
Re: kthread_stop insanity (Re: [[DEBUG] force] 2642458962: BUG: unable to handle kernel paging request at ffffc90000997f18) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-27 19:20 +0200
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