From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Sun, 30 Jul 2006 10:03:52 +0000 (-0700)
Subject: [PATCH] pi-futex: missing pi_waiters plist initialization
X-Git-Tag: v2.6.18-rc4~107
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b50f60ceeef2e38e529737c0260d9543939915ad;p=linux-2.6

[PATCH] pi-futex: missing pi_waiters plist initialization

Initialize init task's pi_waiters plist.  Otherwise cpu hotplug of cpu 0
might crash, since rt_mutex_getprio() accesses an uninitialized list head.

call chain which led to crash:

take_cpu_down
sched_idle_next
__setscheduler
rt_mutex_getprio

Using PLIST_HEAD_INIT in the INIT_TASK macro doesn't work unfortunately,
since the pi_waiters member is only conditionally present.

Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/kernel/sched.c b/kernel/sched.c
index de440b220b..a2be2d0552 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6766,6 +6766,11 @@ void __init sched_init(void)
 	}
 
 	set_load_weight(&init_task);
+
+#ifdef CONFIG_RT_MUTEXES
+	plist_head_init(&init_task.pi_waiters, &init_task.pi_lock);
+#endif
+
 	/*
 	 * The boot idle thread does lazy MMU switching as well:
 	 */