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Subject[PATCH 3/5] exit: wait: drop tasklist_lock before psig->c* accounting
wait_task_zombie() no longer needs tasklist_lock to accumulate the
psig->c* counters, we can drop it right after cmpxchg(exit_state).

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/exit.c | 10 ++++------
1 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 40d53de..e0914eb 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1003,6 +1003,10 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
EXIT_TRACE : EXIT_DEAD;
if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
return 0;
+ /*
+ * We own this thread, nobody else can reap it.
+ */
+ read_unlock(&tasklist_lock);

/*
* Check thread_group_leader() to exclude the traced sub-threads.
@@ -1062,12 +1066,6 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
spin_unlock_irq(&current->sighand->siglock);
}

- /*
- * Now we are sure this task is interesting, and no other
- * thread can reap it because we its state == DEAD/TRACE.
- */
- read_unlock(&tasklist_lock);
-
retval = wo->wo_rusage
? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
status = (p->signal->flags & SIGNAL_GROUP_EXIT)
--
1.5.5.1


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