[PATCH] spin_lock_*(): Always evaluate second argument

[PATCH] spin_lock_*(): Always evaluate second argument

[Bart Van Assche]

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() and
spin_lock_nest_lock().

This patch has the intentional side effect 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 <bvanassche@acm.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: David S. Miller <davem@davemloft.net>
---
 include/linux/spinlock.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index 3f2867f..32b16cc 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -197,8 +197,10 @@ 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)
-# define raw_spin_lock_nest_lock(lock, nest_lock)	_raw_spin_lock(lock)
+# define raw_spin_lock_nested(lock, subclass)		\
+	((void)(subclass), _raw_spin_lock(lock))
+# define raw_spin_lock_nest_lock(lock, nest_lock)	\
+	((void)(nest_lock), _raw_spin_lock(lock))
 #endif
 
 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
-- 
1.8.4.5

Re: [PATCH] spin_lock_*(): Always evaluate second argument

[David Rientjes]

On Mon, 16 Jun 2014, Bart Van Assche wrote:

> 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() and
> spin_lock_nest_lock().
> 
> This patch has the intentional side effect 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 <bvanassche@acm.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: David S. Miller <davem@davemloft.net>

Acked-by: David Rientjes <rientjes@google.com>

Re: [PATCH] spin_lock_*(): Always evaluate second argument

[David Rientjes]

On Mon, 16 Jun 2014, Bart Van Assche wrote:

> 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() and
> spin_lock_nest_lock().
> 
> This patch has the intentional side effect 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 <bvanassche@acm.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: David S. Miller <davem@davemloft.net>

Bart, could you please resend this patch with my acked-by?