From 4999201a59ef555f9105d2bb2459ed895627f7aa Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Fri, 8 Aug 2014 12:35:36 +0200 Subject: [PATCH] locking/spinlocks: Always evaluate the second argument of spin_lock_nested() Evaluating a macro argument only if certain configuration options have been selected is confusing and error-prone. Hence always evaluate the second argument of spin_lock_nested(). An intentional side effect of this patch is that it avoids that the following warning is reported for netif_addr_lock_nested() when building with CONFIG_DEBUG_LOCK_ALLOC=n and with W=1: include/linux/netdevice.h: In function 'netif_addr_lock_nested': include/linux/netdevice.h:2865:6: warning: variable 'subclass' set but not used [-Wunused-but-set-variable] int subclass = SINGLE_DEPTH_NESTING; ^ Signed-off-by: Bart Van Assche Signed-off-by: Peter Zijlstra Cc: David Rientjes Cc: David S. Miller Cc: Andrew Morton Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Paul E. McKenney Link: http://lkml.kernel.org/r/53E4A7F8.1040700@acm.org Signed-off-by: Ingo Molnar --- include/linux/spinlock.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 3f2867ff0ced..262ba4ef9a8e 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -197,7 +197,13 @@ static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock) _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \ } while (0) #else -# define raw_spin_lock_nested(lock, subclass) _raw_spin_lock(lock) +/* + * Always evaluate the 'subclass' argument to avoid that the compiler + * warns about set-but-not-used variables when building with + * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1. + */ +# define raw_spin_lock_nested(lock, subclass) \ + _raw_spin_lock(((void)(subclass), (lock))) # define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock) #endif