android_kernel_google_msm/kernel/rwsem.c
Livio Soares c7af77b584 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>
2007-12-18 15:21:13 +01:00

148 lines
2.6 KiB
C

/* kernel/rwsem.c: R/W semaphores, public implementation
*
* Written by David Howells (dhowells@redhat.com).
* Derived from asm-i386/semaphore.h
*/
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/rwsem.h>
#include <asm/system.h>
#include <asm/atomic.h>
/*
* lock for reading
*/
void __sched down_read(struct rw_semaphore *sem)
{
might_sleep();
rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
}
EXPORT_SYMBOL(down_read);
/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
int down_read_trylock(struct rw_semaphore *sem)
{
int ret = __down_read_trylock(sem);
if (ret == 1)
rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
return ret;
}
EXPORT_SYMBOL(down_read_trylock);
/*
* lock for writing
*/
void __sched down_write(struct rw_semaphore *sem)
{
might_sleep();
rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
}
EXPORT_SYMBOL(down_write);
/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
int down_write_trylock(struct rw_semaphore *sem)
{
int ret = __down_write_trylock(sem);
if (ret == 1)
rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
return ret;
}
EXPORT_SYMBOL(down_write_trylock);
/*
* release a read lock
*/
void up_read(struct rw_semaphore *sem)
{
rwsem_release(&sem->dep_map, 1, _RET_IP_);
__up_read(sem);
}
EXPORT_SYMBOL(up_read);
/*
* release a write lock
*/
void up_write(struct rw_semaphore *sem)
{
rwsem_release(&sem->dep_map, 1, _RET_IP_);
__up_write(sem);
}
EXPORT_SYMBOL(up_write);
/*
* downgrade write lock to read lock
*/
void downgrade_write(struct rw_semaphore *sem)
{
/*
* lockdep: a downgraded write will live on as a write
* dependency.
*/
__downgrade_write(sem);
}
EXPORT_SYMBOL(downgrade_write);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
void down_read_nested(struct rw_semaphore *sem, int subclass)
{
might_sleep();
rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
}
EXPORT_SYMBOL(down_read_nested);
void down_read_non_owner(struct rw_semaphore *sem)
{
might_sleep();
__down_read(sem);
}
EXPORT_SYMBOL(down_read_non_owner);
void down_write_nested(struct rw_semaphore *sem, int subclass)
{
might_sleep();
rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
}
EXPORT_SYMBOL(down_write_nested);
void up_read_non_owner(struct rw_semaphore *sem)
{
__up_read(sem);
}
EXPORT_SYMBOL(up_read_non_owner);
#endif