On Thu, 12 Apr 2012 12:09:53 +0400 Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> 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? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>