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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 16 Nov 2017 16:48:48 +0100
Subject: [PATCH] locking/rtmutex: re-init the wait_lock in
rt_mutex_init_proxy_locked()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.17-rt8.tar.xz
We could provide a key-class for the lockdep (and fixup all callers) or
move the init to all callers (like it was) in order to avoid lockdep
seeing a double-lock of the wait_lock.
Reported-by: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/locking/rtmutex.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -2280,6 +2280,14 @@ void rt_mutex_init_proxy_locked(struct r
struct task_struct *proxy_owner)
{
__rt_mutex_init(lock, NULL, NULL);
+#ifdef CONFIG_DEBUG_SPINLOCK
+ /*
+ * get another key class for the wait_lock. LOCK_PI and UNLOCK_PI is
+ * holding the ->wait_lock of the proxy_lock while unlocking a sleeping
+ * lock.
+ */
+ raw_spin_lock_init(&lock->wait_lock);
+#endif
debug_rt_mutex_proxy_lock(lock, proxy_owner);
rt_mutex_set_owner(lock, proxy_owner);
}
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