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wait: use EXIT_TRACE only if thread_group_leader(zombie)

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wait_task_zombie() always uses EXIT_TRACE/ptrace_unlink() if
ptrace_reparented().  This is suboptimal and a bit confusing: we do not
need do_notify_parent(p) if !thread_group_leader(p) and in this case we
also do not need ptrace_unlink(), we can rely on ptrace_release_task().

Change wait_task_zombie() to check thread_group_leader() along with
ptrace_reparented() and simplify the final p->exit_state transition.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Tested-by: Michal Schmidt <mschmidt@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Lennart Poettering <lpoetter@redhat.com>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2014-04-07 15:38:43 -07:00 committed by Linus Torvalds
parent abd50b39e7
commit b436069059
1 changed files with 7 additions and 10 deletions
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15
kernel/exit.c
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@ -1040,7 +1040,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
/*
* Move the task's state to DEAD/TRACE, only one thread can do this.
*/
state = traced ? EXIT_TRACE : EXIT_DEAD;
state = traced && thread_group_leader(p) ? EXIT_TRACE : EXIT_DEAD;
if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
return 0;
/*
@ -1140,18 +1140,15 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
if (!retval)
retval = pid;
if (traced) {
if (state == EXIT_TRACE) {
write_lock_irq(&tasklist_lock);
/* We dropped tasklist, ptracer could die and untrace */
ptrace_unlink(p);
/*
* If this is not a sub-thread, notify the parent.
* If parent wants a zombie, don't release it now.
*/
state = EXIT_DEAD;
if (thread_group_leader(p) &&
!do_notify_parent(p, p->exit_signal))
/* If parent wants a zombie, don't release it now */
state = EXIT_ZOMBIE;
if (do_notify_parent(p, p->exit_signal))
state = EXIT_DEAD;
p->exit_state = state;
write_unlock_irq(&tasklist_lock);
}