This patch optimize zap_threads() for the case when there are
no ->mm users except the current's thread group. In that case
we can avoid 'for_each_process()' loop.
It also adds a useful invariant: SIGNAL_GROUP_EXIT (if checked
under ->siglock) always implies that all threads (except may be
current) have pending SIGKILL.
Signed-off-by: Oleg Nesterov <[email protected]>
--- MM/fs/exec.c~2_optmz 2006-04-09 02:33:28.000000000 +0400
+++ MM/fs/exec.c 2006-04-09 03:06:43.000000000 +0400
@@ -1383,13 +1383,7 @@ static void format_corename(char *corena
static void zap_process(struct task_struct *start)
{
struct task_struct *t;
- unsigned long flags;
- /*
- * start->sighand can't disappear, but may be
- * changed by de_thread()
- */
- lock_task_sighand(start, &flags);
start->signal->flags = SIGNAL_GROUP_EXIT;
start->signal->group_stop_count = 0;
@@ -1401,40 +1395,51 @@ static void zap_process(struct task_stru
signal_wake_up(t, 1);
}
} while ((t = next_thread(t)) != start);
-
- unlock_task_sighand(start, &flags);
}
static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
int exit_code)
{
struct task_struct *g, *p;
+ unsigned long flags;
int err = -EAGAIN;
spin_lock_irq(&tsk->sighand->siglock);
if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT)) {
- tsk->signal->flags = SIGNAL_GROUP_EXIT;
tsk->signal->group_exit_code = exit_code;
- tsk->signal->group_stop_count = 0;
+ zap_process(tsk);
err = 0;
}
spin_unlock_irq(&tsk->sighand->siglock);
if (err)
return err;
+ if (atomic_read(&mm->mm_users) == mm->core_waiters + 1)
+ goto done;
+
rcu_read_lock();
for_each_process(g) {
+ if (g == tsk->group_leader)
+ continue;
+
p = g;
do {
if (p->mm) {
- if (p->mm == mm)
+ if (p->mm == mm) {
+ /*
+ * p->sighand can't disappear, but
+ * may be changed by de_thread()
+ */
+ lock_task_sighand(p, &flags);
zap_process(p);
+ unlock_task_sighand(p, &flags);
+ }
break;
}
} while ((p = next_thread(p)) != g);
}
rcu_read_unlock();
-
+done:
return mm->core_waiters;
}
-
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