-/* 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/rwsem.h>
#include <linux/sched.h>
-#include <linux/module.h>
+#include <linux/export.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 RWSEM_DEBUG
-void rwsemtrace(struct rw_semaphore *sem, const char *str)
+int rwsem_is_locked(struct rw_semaphore *sem)
{
- if (sem->debug)
- printk("[%d] %s({%d,%d})\n",
- current->pid,str,sem->activity,list_empty(&sem->wait_list)?0:1);
+ int ret = 1;
+ unsigned long flags;
+
+ if (raw_spin_trylock_irqsave(&sem->wait_lock, flags)) {
+ ret = (sem->activity != 0);
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
+ }
+ return ret;
}
-#endif
+EXPORT_SYMBOL(rwsem_is_locked);
/*
* initialise the semaphore
*/
-void fastcall init_rwsem(struct rw_semaphore *sem)
+void __init_rwsem(struct rw_semaphore *sem, const char *name,
+ struct lock_class_key *key)
{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ /*
+ * Make sure we are not reinitializing a held semaphore:
+ */
+ debug_check_no_locks_freed((void *)sem, sizeof(*sem));
+ lockdep_init_map(&sem->dep_map, name, key, 0);
+#endif
sem->activity = 0;
- spin_lock_init(&sem->wait_lock);
+ raw_spin_lock_init(&sem->wait_lock);
INIT_LIST_HEAD(&sem->wait_list);
-#if RWSEM_DEBUG
- sem->debug = 0;
-#endif
}
+EXPORT_SYMBOL(__init_rwsem);
/*
- * handle the lock being released whilst there are processes blocked on it that can now run
+ * handle the lock release when processes blocked on it that can now run
* - if we come here, then:
* - the 'active count' _reached_ zero
* - the 'waiting count' is non-zero
* - the spinlock must be held by the caller
- * - woken process blocks are discarded from the list after having flags zeroised
+ * - 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");
-
- 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);
- waiter->flags = 0;
- wake_up_process(waiter->task);
+ tsk = waiter->task;
+ /* Don't touch waiter after ->task has been NULLed */
+ smp_mb();
+ waiter->task = NULL;
+ wake_up_process(tsk);
+ put_task_struct(tsk);
goto out;
}
- /* grant an infinite number of read locks to the readers at the front of the queue */
+ /* grant an infinite number of read locks to 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);
- waiter->flags = 0;
- wake_up_process(waiter->task);
+ tsk = waiter->task;
+ smp_mb();
+ waiter->task = NULL;
+ wake_up_process(tsk);
+ put_task_struct(tsk);
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");
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);
- waiter->flags = 0;
- wake_up_process(waiter->task);
+ tsk = waiter->task;
+ smp_mb();
+ waiter->task = NULL;
+ wake_up_process(tsk);
+ put_task_struct(tsk);
return sem;
}
/*
* get a read lock on the semaphore
*/
-void fastcall __down_read(struct rw_semaphore *sem)
+void __sched __down_read(struct rw_semaphore *sem)
{
struct rwsem_waiter waiter;
struct task_struct *tsk;
+ unsigned long flags;
- rwsemtrace(sem,"Entering __down_read");
-
- spin_lock(&sem->wait_lock);
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
- 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);
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
goto out;
}
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);
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
/* wait to be given the lock */
for (;;) {
- if (!waiter.flags)
+ if (!waiter.task)
break;
schedule();
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
}
tsk->state = TASK_RUNNING;
-
out:
- rwsemtrace(sem,"Leaving __down_read");
+ ;
}
/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
-int fastcall __down_read_trylock(struct rw_semaphore *sem)
+int __down_read_trylock(struct rw_semaphore *sem)
{
+ unsigned long flags;
int ret = 0;
- rwsemtrace(sem,"Entering __down_read_trylock");
- spin_lock(&sem->wait_lock);
- if (sem->activity>=0 && list_empty(&sem->wait_list)) {
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
/* granted */
sem->activity++;
ret = 1;
}
- spin_unlock(&sem->wait_lock);
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
- rwsemtrace(sem,"Leaving __down_read_trylock");
return ret;
}
/*
* get a write lock on the semaphore
- * - note that we increment the waiting count anyway to indicate an exclusive lock
+ * - we increment the waiting count anyway to indicate an exclusive lock
*/
-void fastcall __down_write(struct rw_semaphore *sem)
+void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
{
struct rwsem_waiter waiter;
struct task_struct *tsk;
+ unsigned long flags;
- rwsemtrace(sem,"Entering __down_write");
-
- spin_lock(&sem->wait_lock);
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
- 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);
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
goto out;
}
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);
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
/* wait to be given the lock */
for (;;) {
- if (!waiter.flags)
+ if (!waiter.task)
break;
schedule();
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
}
tsk->state = TASK_RUNNING;
-
out:
- rwsemtrace(sem,"Leaving __down_write");
+ ;
+}
+
+void __sched __down_write(struct rw_semaphore *sem)
+{
+ __down_write_nested(sem, 0);
}
/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
-int fastcall __down_write_trylock(struct rw_semaphore *sem)
+int __down_write_trylock(struct rw_semaphore *sem)
{
+ unsigned long flags;
int ret = 0;
- rwsemtrace(sem,"Entering __down_write_trylock");
- spin_lock(&sem->wait_lock);
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
- 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);
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
- rwsemtrace(sem,"Leaving __down_write_trylock");
return ret;
}
/*
* release a read lock on the semaphore
*/
-void fastcall __up_read(struct rw_semaphore *sem)
+void __up_read(struct rw_semaphore *sem)
{
- rwsemtrace(sem,"Entering __up_read");
+ unsigned long flags;
- spin_lock(&sem->wait_lock);
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
- 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");
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
}
/*
* release a write lock on the semaphore
*/
-void fastcall __up_write(struct rw_semaphore *sem)
+void __up_write(struct rw_semaphore *sem)
{
- rwsemtrace(sem,"Entering __up_write");
+ unsigned long flags;
- spin_lock(&sem->wait_lock);
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
sem->activity = 0;
if (!list_empty(&sem->wait_list))
sem = __rwsem_do_wake(sem, 1);
- spin_unlock(&sem->wait_lock);
-
- rwsemtrace(sem,"Leaving __up_write");
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
}
/*
* downgrade a write lock into a read lock
* - just wake up any readers at the front of the queue
*/
-void fastcall __downgrade_write(struct rw_semaphore *sem)
+void __downgrade_write(struct rw_semaphore *sem)
{
- rwsemtrace(sem,"Entering __downgrade_write");
+ unsigned long flags;
- spin_lock(&sem->wait_lock);
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
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");
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
}
-EXPORT_SYMBOL(init_rwsem);
-EXPORT_SYMBOL(__down_read);
-EXPORT_SYMBOL(__down_read_trylock);
-EXPORT_SYMBOL(__down_write);
-EXPORT_SYMBOL(__down_write_trylock);
-EXPORT_SYMBOL(__up_read);
-EXPORT_SYMBOL(__up_write);
-EXPORT_SYMBOL(__downgrade_write);
-#if RWSEM_DEBUG
-EXPORT_SYMBOL(rwsemtrace);
-#endif
projects / linux-flexiantxendom0-3.2.10.git / blobdiff