From: Andrew Morton 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 for reporting and testing. Cc: Ingo Molnar Cc: Signed-off-by: Andrew Morton --- lib/spinlock_debug.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff -puN lib/spinlock_debug.c~disable-debugging-version-of-write_lock lib/spinlock_debug.c --- a/lib/spinlock_debug.c~disable-debugging-version-of-write_lock +++ a/lib/spinlock_debug.c @@ -162,6 +162,7 @@ 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; @@ -184,12 +185,12 @@ 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) @@ -235,6 +236,7 @@ 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; @@ -257,12 +259,12 @@ 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); } _