linux-kernel - [PATCH] futex: move debug_rt_mutex_free

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Date:   Wed, 8 Mar 2017 16:29:02 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, mingo@...nel.org, juri.lelli@....com,
        rostedt@...dmis.org, xlpang@...hat.com,
        linux-kernel@...r.kernel.org, mathieu.desnoyers@...icios.com,
        jdesfossez@...icios.com, bristot@...hat.com, dvhart@...radead.org
Subject: [PATCH] futex: move debug_rt_mutex_free_waiter() further down

Without this, futex_requeue_pi_signal_restart will trigger

|kernel BUG at locking/rtmutex_common.h:55!
|Call Trace:
| rt_mutex_cleanup_proxy_lock+0x54/0x90
| futex_wait_requeue_pi.constprop.21+0x387/0x4d0
| do_futex+0x289/0xbf0
|RIP: remove_waiter+0x157/0x170 RSP: ffffc90000e0fbe0

with BUG 2222222222222222 != pointer once this patch is applied.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/futex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 00ec4a01d3f5..73abfe0da4d0 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3046,11 +3046,11 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 		WARN_ON(!q.pi_state);
 		pi_mutex = &q.pi_state->pi_mutex;
 		ret = rt_mutex_wait_proxy_lock(pi_mutex, to, &rt_waiter);
-		debug_rt_mutex_free_waiter(&rt_waiter);
 
 		spin_lock(q.lock_ptr);
 		if (ret && !rt_mutex_cleanup_proxy_lock(pi_mutex, &rt_waiter))
 			ret = 0;
+		debug_rt_mutex_free_waiter(&rt_waiter);
 
 		/*
 		 * Fixup the pi_state owner and possibly acquire the lock if we
-- 
2.11.0