[patch 07/20] disable debugging version of write_lock()

[Greg KH <gregkh@suse.de>]

[-- Attachment #1: disable-debugging-version-of-write_lock.patch --]
[-- Type: text/plain, Size: 1917 bytes --]

-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Andrew Morton <akpm@osdl.org>

We've confirmed that the debug version of write_lock() can get stuck for long
enough to cause NMI watchdog timeouts and hence a crash.

We don't know why, yet.   Disable it for now.

Also disable the similar read_lock() code.  Just in case.

Thanks to Dave Olson <olson@unixfolk.com> for reporting and testing.

Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 lib/spinlock_debug.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- linux-2.6.17.8.orig/lib/spinlock_debug.c
+++ linux-2.6.17.8/lib/spinlock_debug.c
@@ -137,6 +137,7 @@ static void rwlock_bug(rwlock_t *lock, c
 
 #define RWLOCK_BUG_ON(cond, lock, msg) if (unlikely(cond)) rwlock_bug(lock, msg)
 
+#if 0		/* __write_lock_debug() can lock up - maybe this can too? */
 static void __read_lock_debug(rwlock_t *lock)
 {
 	int print_once = 1;
@@ -159,12 +160,12 @@ static void __read_lock_debug(rwlock_t *
 		}
 	}
 }
+#endif
 
 void _raw_read_lock(rwlock_t *lock)
 {
 	RWLOCK_BUG_ON(lock->magic != RWLOCK_MAGIC, lock, "bad magic");
-	if (unlikely(!__raw_read_trylock(&lock->raw_lock)))
-		__read_lock_debug(lock);
+	__raw_read_lock(&lock->raw_lock);
 }
 
 int _raw_read_trylock(rwlock_t *lock)
@@ -210,6 +211,7 @@ static inline void debug_write_unlock(rw
 	lock->owner_cpu = -1;
 }
 
+#if 0		/* This can cause lockups */
 static void __write_lock_debug(rwlock_t *lock)
 {
 	int print_once = 1;
@@ -232,12 +234,12 @@ static void __write_lock_debug(rwlock_t 
 		}
 	}
 }
+#endif
 
 void _raw_write_lock(rwlock_t *lock)
 {
 	debug_write_lock_before(lock);
-	if (unlikely(!__raw_write_trylock(&lock->raw_lock)))
-		__write_lock_debug(lock);
+	__raw_write_lock(&lock->raw_lock);
 	debug_write_lock_after(lock);
 }
 

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