sched: mark rwsem functions as __sched for wchan/profiling

This following commit

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=fdf8cb0909b531f9ae8f9b9d7e4eb35ba3505f07

un-inlined a low-level rwsem function, but did not mark it as __sched.
The result is that it now shows up as thread wchan (which also affects
/proc/profile stats).  The following simple patch fixes this by properly
marking rwsem_down_failed_common() as a __sched function.

Also in this patch, which is up for discussion, marks down_read() and
down_write() proper as __sched.  For profiling, it is pretty much
useless to know that a semaphore is beig help - it is necessary to know
_which_ one.  By going up another frame on the stack, the information
becomes much more useful.

In summary, the below change to lib/rwsem.c should be applied; the
changes to kernel/rwsem.c could be applied if other kernel hackers agree
with my proposal that down_read()/down_write() in the profile is not
enough.

[ akpm@linux-foundation.org: build fix ]
Signed-off-by: Livio Soares <livio@eecg.toronto.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/rwsem.c

@@ -6,6 +6,7 @@
 
 #include <linux/types.h>
 #include <linux/kernel.h>
+#include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/rwsem.h>
 
@@ -15,7 +16,7 @@
 /*
  * lock for reading
  */
-void down_read(struct rw_semaphore *sem)
+void __sched down_read(struct rw_semaphore *sem)
 {
 	might_sleep();
 	rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
@@ -42,7 +43,7 @@ EXPORT_SYMBOL(down_read_trylock);
 /*
  * lock for writing
  */
-void down_write(struct rw_semaphore *sem)
+void __sched down_write(struct rw_semaphore *sem)
 {
 	might_sleep();
 	rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);

lib/rwsem.c

@@ -146,7 +146,7 @@ __rwsem_do_wake(struct rw_semaphore *sem, int downgrading)
 /*
  * wait for a lock to be granted
  */
-static struct rw_semaphore *
+static struct rw_semaphore __sched *
 rwsem_down_failed_common(struct rw_semaphore *sem,
 			struct rwsem_waiter *waiter, signed long adjustment)
 {