-/* rwsem-spinlock.c: R/W semaphores: contention handling functions for
- * generic spinlock implementation
+/* rwsem-spinlock.c: R/W semaphores: contention handling functions for generic spinlock
+ * implementation
*
* Copyright (c) 2001 David Howells (dhowells@redhat.com).
* - Derived partially from idea by Andrea Arcangeli <andrea@suse.de>
#include <linux/module.h>
struct rwsem_waiter {
- struct list_head list;
- struct task_struct *task;
- unsigned int flags;
+ struct list_head list;
+ struct task_struct *task;
+ unsigned int flags;
#define RWSEM_WAITING_FOR_READ 0x00000001
#define RWSEM_WAITING_FOR_WRITE 0x00000002
};
{
if (sem->debug)
printk("[%d] %s({%d,%d})\n",
- current->pid, str, sem->activity,
- list_empty(&sem->wait_list) ? 0 : 1);
+ current->pid,str,sem->activity,list_empty(&sem->wait_list)?0:1);
}
#endif
}
/*
- * handle the lock release when processes blocked on it that can now run
+ * handle the lock being released whilst there are processes blocked on it that can now run
* - if we come here, then:
* - the 'active count' _reached_ zero
* - the 'waiting count' is non-zero
* - woken process blocks are discarded from the list after having task zeroed
* - writers are only woken if wakewrite is non-zero
*/
-static inline struct rw_semaphore *
-__rwsem_do_wake(struct rw_semaphore *sem, int wakewrite)
+static inline struct rw_semaphore *__rwsem_do_wake(struct rw_semaphore *sem, int wakewrite)
{
struct rwsem_waiter *waiter;
struct task_struct *tsk;
int woken;
- rwsemtrace(sem, "Entering __rwsem_do_wake");
+ rwsemtrace(sem,"Entering __rwsem_do_wake");
- waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
+ waiter = list_entry(sem->wait_list.next,struct rwsem_waiter,list);
if (!wakewrite) {
if (waiter->flags & RWSEM_WAITING_FOR_WRITE)
goto dont_wake_writers;
}
- /* if we are allowed to wake writers try to grant a single write lock
- * if there's a writer at the front of the queue
- * - we leave the 'waiting count' incremented to signify potential
- * contention
+ /* if we are allowed to wake writers try to grant a single write lock if there's a
+ * writer at the front of the queue
+ * - we leave the 'waiting count' incremented to signify potential contention
*/
if (waiter->flags & RWSEM_WAITING_FOR_WRITE) {
sem->activity = -1;
list_del(&waiter->list);
tsk = waiter->task;
- /* Don't touch waiter after ->task has been NULLed */
mb();
waiter->task = NULL;
wake_up_process(tsk);
goto out;
}
- /* grant an infinite number of read locks to the front of the queue */
+ /* grant an infinite number of read locks to the readers at the front of the queue */
dont_wake_writers:
woken = 0;
- while (waiter->flags & RWSEM_WAITING_FOR_READ) {
+ while (waiter->flags&RWSEM_WAITING_FOR_READ) {
struct list_head *next = waiter->list.next;
list_del(&waiter->list);
woken++;
if (list_empty(&sem->wait_list))
break;
- waiter = list_entry(next, struct rwsem_waiter, list);
+ waiter = list_entry(next,struct rwsem_waiter,list);
}
sem->activity += woken;
out:
- rwsemtrace(sem, "Leaving __rwsem_do_wake");
+ rwsemtrace(sem,"Leaving __rwsem_do_wake");
return sem;
}
/*
* wake a single writer
*/
-static inline struct rw_semaphore *
-__rwsem_wake_one_writer(struct rw_semaphore *sem)
+static inline struct rw_semaphore *__rwsem_wake_one_writer(struct rw_semaphore *sem)
{
struct rwsem_waiter *waiter;
struct task_struct *tsk;
sem->activity = -1;
- waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
+ waiter = list_entry(sem->wait_list.next,struct rwsem_waiter,list);
list_del(&waiter->list);
tsk = waiter->task;
/*
* get a read lock on the semaphore
*/
-void fastcall __sched __down_read(struct rw_semaphore *sem)
+void fastcall __down_read(struct rw_semaphore *sem)
{
struct rwsem_waiter waiter;
struct task_struct *tsk;
- rwsemtrace(sem, "Entering __down_read");
+ rwsemtrace(sem,"Entering __down_read");
spin_lock(&sem->wait_lock);
- if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
+ if (sem->activity>=0 && list_empty(&sem->wait_list)) {
/* granted */
sem->activity++;
spin_unlock(&sem->wait_lock);
}
tsk = current;
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+ set_task_state(tsk,TASK_UNINTERRUPTIBLE);
/* set up my own style of waitqueue */
waiter.task = tsk;
waiter.flags = RWSEM_WAITING_FOR_READ;
get_task_struct(tsk);
- list_add_tail(&waiter.list, &sem->wait_list);
+ list_add_tail(&waiter.list,&sem->wait_list);
/* we don't need to touch the semaphore struct anymore */
spin_unlock(&sem->wait_lock);
tsk->state = TASK_RUNNING;
out:
- rwsemtrace(sem, "Leaving __down_read");
+ rwsemtrace(sem,"Leaving __down_read");
}
/*
int fastcall __down_read_trylock(struct rw_semaphore *sem)
{
int ret = 0;
- rwsemtrace(sem, "Entering __down_read_trylock");
+ rwsemtrace(sem,"Entering __down_read_trylock");
spin_lock(&sem->wait_lock);
- if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
+ if (sem->activity>=0 && list_empty(&sem->wait_list)) {
/* granted */
sem->activity++;
ret = 1;
spin_unlock(&sem->wait_lock);
- rwsemtrace(sem, "Leaving __down_read_trylock");
+ rwsemtrace(sem,"Leaving __down_read_trylock");
return ret;
}
/*
* get a write lock on the semaphore
- * - we increment the waiting count anyway to indicate an exclusive lock
+ * - note that we increment the waiting count anyway to indicate an exclusive lock
*/
-void fastcall __sched __down_write(struct rw_semaphore *sem)
+void fastcall __down_write(struct rw_semaphore *sem)
{
struct rwsem_waiter waiter;
struct task_struct *tsk;
- rwsemtrace(sem, "Entering __down_write");
+ rwsemtrace(sem,"Entering __down_write");
spin_lock(&sem->wait_lock);
- if (sem->activity == 0 && list_empty(&sem->wait_list)) {
+ if (sem->activity==0 && list_empty(&sem->wait_list)) {
/* granted */
sem->activity = -1;
spin_unlock(&sem->wait_lock);
}
tsk = current;
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+ set_task_state(tsk,TASK_UNINTERRUPTIBLE);
/* set up my own style of waitqueue */
waiter.task = tsk;
waiter.flags = RWSEM_WAITING_FOR_WRITE;
get_task_struct(tsk);
- list_add_tail(&waiter.list, &sem->wait_list);
+ list_add_tail(&waiter.list,&sem->wait_list);
/* we don't need to touch the semaphore struct anymore */
spin_unlock(&sem->wait_lock);
tsk->state = TASK_RUNNING;
out:
- rwsemtrace(sem, "Leaving __down_write");
+ rwsemtrace(sem,"Leaving __down_write");
}
/*
int fastcall __down_write_trylock(struct rw_semaphore *sem)
{
int ret = 0;
- rwsemtrace(sem, "Entering __down_write_trylock");
+ rwsemtrace(sem,"Entering __down_write_trylock");
spin_lock(&sem->wait_lock);
- if (sem->activity == 0 && list_empty(&sem->wait_list)) {
+ if (sem->activity==0 && list_empty(&sem->wait_list)) {
/* granted */
sem->activity = -1;
ret = 1;
spin_unlock(&sem->wait_lock);
- rwsemtrace(sem, "Leaving __down_write_trylock");
+ rwsemtrace(sem,"Leaving __down_write_trylock");
return ret;
}
*/
void fastcall __up_read(struct rw_semaphore *sem)
{
- rwsemtrace(sem, "Entering __up_read");
+ rwsemtrace(sem,"Entering __up_read");
spin_lock(&sem->wait_lock);
- if (--sem->activity == 0 && !list_empty(&sem->wait_list))
+ if (--sem->activity==0 && !list_empty(&sem->wait_list))
sem = __rwsem_wake_one_writer(sem);
spin_unlock(&sem->wait_lock);
- rwsemtrace(sem, "Leaving __up_read");
+ rwsemtrace(sem,"Leaving __up_read");
}
/*
*/
void fastcall __up_write(struct rw_semaphore *sem)
{
- rwsemtrace(sem, "Entering __up_write");
+ rwsemtrace(sem,"Entering __up_write");
spin_lock(&sem->wait_lock);
spin_unlock(&sem->wait_lock);
- rwsemtrace(sem, "Leaving __up_write");
+ rwsemtrace(sem,"Leaving __up_write");
}
/*
*/
void fastcall __downgrade_write(struct rw_semaphore *sem)
{
- rwsemtrace(sem, "Entering __downgrade_write");
+ rwsemtrace(sem,"Entering __downgrade_write");
spin_lock(&sem->wait_lock);
sem->activity = 1;
if (!list_empty(&sem->wait_list))
- sem = __rwsem_do_wake(sem, 0);
+ sem = __rwsem_do_wake(sem,0);
spin_unlock(&sem->wait_lock);
- rwsemtrace(sem, "Leaving __downgrade_write");
+ rwsemtrace(sem,"Leaving __downgrade_write");
}
EXPORT_SYMBOL(init_rwsem);
git://git.onelab.eu / linux-2.6.git / blobdiff