From 46f382d2b69d2221086b823f0dbc8f32c027cac2 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Fri, 8 Feb 2008 04:19:19 -0800
Subject: [PATCH] uglify while_each_pid_task() to make sure we don't count the
execing pricess twice
There is a window when de_thread() switches the leader and drops
tasklist_lock. In that window do_each_pid_task(PIDTYPE_PID) finds both new
and old leaders.
The problem is pretty much theoretical and probably can be ignored. Currently
the only users of do_each_pid_task(PIDTYPE_PID) are send_sigio/send_sigurg, so
they can send the signal to the same process twice.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/pid.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/include/linux/pid.h b/include/linux/pid.h
index b91f4732dc1b7..f84d532b5d23e 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -152,7 +152,13 @@ pid_t pid_vnr(struct pid *pid);
hlist_for_each_entry_rcu((task), pos___, \
&pid->tasks[type], pids[type].node) {
+ /*
+ * Both old and new leaders may be attached to
+ * the same pid in the middle of de_thread().
+ */
#define while_each_pid_task(pid, type, task) \
+ if (type == PIDTYPE_PID) \
+ break; \
} \
} while (0)
--
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