[PATCH 3/3] do __unhash_process() under ->siglock

From: Oleg Nesterov
Date: Wed Feb 22 2006 - 17:34:53 EST


This patch moves __unhash_process() call from realease_task()
to __exit_signal(), so __detach_pid() is called with ->siglock
held.

This means we don't need tasklist_lock to iterate over thread
group anymore:

copy_process() was already changed to do attach_pid()
under ->siglock.

Eric's "pidhash-kill-switch_exec_pids.patch" from -mm
changed de_thread() so it doesn't touch PIDTYPE_TGID.

NOTE: de_thread() still needs some attention. It still changes
task->pid lockless. Taking ->sighand.siglock here allows to do
more tasklist_lock removals.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>

--- 2.6.16-rc3/kernel/exit.c~3_FIN 2006-02-23 00:54:28.000000000 +0300
+++ 2.6.16-rc3/kernel/exit.c 2006-02-23 01:00:35.000000000 +0300
@@ -110,6 +110,8 @@ static void __exit_signal(struct task_st
sig = NULL; /* Marker for below. */
}

+ __unhash_process(tsk);
+
tsk->signal = NULL;
cleanup_sighand(tsk);
spin_unlock(&sighand->siglock);
@@ -138,8 +140,6 @@ repeat:
BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
__exit_signal(p);

- __unhash_process(p);
-
/*
* If we are the last non-leader member of the thread
* group, and the leader is zombie, then notify the
-
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