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Commit 72f0b4e2 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

[PATCH] disable debugging version of write_lock() 



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: default avatarIngo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 927cbe8a

lib/spinlock_debug.c

+6 −4
Original line number Diff line number Diff line
@@ -162,6 +162,7 @@ static void rwlock_bug(rwlock_t *lock, const char *msg) 


#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;
@@ -184,12 +185,12 @@ static void __read_lock_debug(rwlock_t *lock) 
		}

	}

}

#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)
@@ -235,6 +236,7 @@ static inline void debug_write_unlock(rwlock_t *lock) 
	lock->owner_cpu = -1;

}



#if 0		/* This can cause lockups */

static void __write_lock_debug(rwlock_t *lock)

{

	int print_once = 1;
@@ -257,12 +259,12 @@ static void __write_lock_debug(rwlock_t *lock) 
		}

	}

}

#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);

}