Messages in this thread | | | Date | Fri, 13 Apr 2012 10:43:11 +0400 | From | Konstantin Khlebnikov <> | Subject | Re: [PATCH 2/2] mm: call complete_vfork_done() after clearing child_tid and flushing rss-counters |
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Andrew Morton wrote: > On Thu, 12 Apr 2012 12:09:53 +0400 > Konstantin Khlebnikov<khlebnikov@openvz.org> wrote: > >> Child should wake ups parent from vfork() only after finishing all operations with >> shared mm. There is no sense to use CLONE_CHILD_CLEARTID together with CLONE_VFORK, >> but it looks more accurate now. >> >> ... >> >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -728,9 +728,6 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm) >> /* Get rid of any cached register state */ >> deactivate_mm(tsk, mm); >> >> - if (tsk->vfork_done) >> - complete_vfork_done(tsk); >> - >> /* >> * If we're exiting normally, clear a user-space tid field if >> * requested. We leave this alone when dying by signal, to leave >> @@ -759,6 +756,13 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm) >> */ >> if (mm) >> sync_mm_rss(mm); >> + >> + /* >> + * All done, finally we can wake up parent and return this mm to him. >> + * Also kthread_stop() uses this completion for synchronization. >> + */ >> + if (tsk->vfork_done) >> + complete_vfork_done(tsk); >> } > > That does look a bit racy. > > But are we really sure that the patch really does fix something? > Because it does increase vfork() latency a tiny bit. > > I'm going to call this a patch against the fork subsystem, not the mm > subsystem. > > I believe that this patch is unrelated to "mm: set task exit code > before complete_vfork_done()", yes?
Yes, unrelated.
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