Re: [patch] IPV4 spinlock_casting

[Ingo Molnar <mingo@elte.hu>]

* Ingo Molnar <mingo@elte.hu> wrote:

> > Fix a compile error in net/ipv4/route.c when RT patch is applied:
> 
> > Index: linux-2.6.13-rc4-RT-V0.7.52-14/net/ipv4/route.c
> 
> are you sure you are seeing this with the -52-14 patch? If yes then 
> please send me your .config.
> 
> the build error showed a more fundamental bug, which had to be solved 
> differently. The problem was the code in route.c, the problem was this:
> 
>  # define rt_hash_lock_addr(slot) NULL
>  # define rt_hash_lock_init()
> 
> where NULL has no type. The solution for the build problem would have 
> been to cast the NULL to spinlock_t *, but we need this spinlock so 
> the correct solution was to add a || defined(PREEMPT_RT) to the #if 
> defined(CONFIG_SMP) line above. Solving the build problem alone only 
> fixes the symptom, not the bug.

it just occured to me that !PREEMPT_RT builds would be affected by the
#else branch, so i committed the build fix below into -52-15.

	Ingo

Index: linux/net/ipv4/route.c
===================================================================
--- linux.orig/net/ipv4/route.c
+++ linux/net/ipv4/route.c
@@ -231,7 +231,7 @@ static spinlock_t	*rt_hash_locks;
 			spin_lock_init(&rt_hash_locks[i]); \
 		}
 #else
-# define rt_hash_lock_addr(slot) NULL
+# define rt_hash_lock_addr(slot) ((spinlock_t *)NULL)
 # define rt_hash_lock_init()
 #endif