Messages in this thread | | | Date | Fri, 29 Jul 2011 16:25:55 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 4/8] coredump_wait: don't call complete_vfork_done() |
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On 07/29, Matt Fleming wrote: > > On Wed, 2011-07-27 at 18:33 +0200, Oleg Nesterov wrote: > > Now that CLONE_VFORK is killable, coredump_wait() no longer needs > > complete_vfork_done(). zap_threads() should find and kill all tasks > > with the same ->mm, this includes our parent if ->vfork_done is set. > > > > mm_release() becomes the only caller, unexport complete_vfork_done(). > > > > Signed-off-by: Oleg Nesterov <oleg@redhat.com> > > Isn't there a subtle change in user-visible behaviour regarding wait() > with this patch? > > Before the patch, if a child dumps its core it will wakeup the parent > which can read the status of the child via wait(), whereas with this > patch applied the parent will actually be killed along with the child.
No.
Please note that if ->vfork_done != NULL, then ->real_parent shares ->mm with us, by definition of CLONE_VFORK.
In this case, with or without this patch, the parent was already killed by zap_threads(). It can never do wait() or something else.
However. before 3/8, it was necessary to wakeup the TASK_UNINTERRUPTIBLE parent, otherwise we deadlock. Once again, it can't do anything, it will die immediately because of fatal_signal_pending().
After 3/8, zap_process()->signal_wake_up(1) wakes up the KILLABLE parent, no need to do complete().
Oleg.
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