Revision 75c3ebd86f9d06e3f3f2f80fbf0bb0d7ae13e249 authored by John Linn on 18 March 2011, 22:19:16 UTC, committed by John Linn on 18 March 2011, 22:20:56 UTC
This change appears to be backward compatible with peep9 also. This was caused by DT 592979. Without this change, the SRAM test does not pass. This change is small as it only sets the SET_BLS bit in the set_opmode register.
1 parent 142d225
rwsem-spinlock.c
/* 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>
* - Derived also from comments by Linus
*/
#include <linux/rwsem.h>
#include <linux/sched.h>
#include <linux/module.h>
struct rwsem_waiter {
struct list_head list;
struct task_struct *task;
unsigned int flags;
#define RWSEM_WAITING_FOR_READ 0x00000001
#define RWSEM_WAITING_FOR_WRITE 0x00000002
};
int rwsem_is_locked(struct rw_semaphore *sem)
{
int ret = 1;
unsigned long flags;
if (spin_trylock_irqsave(&sem->wait_lock, flags)) {
ret = (sem->activity != 0);
spin_unlock_irqrestore(&sem->wait_lock, flags);
}
return ret;
}
EXPORT_SYMBOL(rwsem_is_locked);
/*
* initialise the semaphore
*/
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);
INIT_LIST_HEAD(&sem->wait_list);
}
EXPORT_SYMBOL(__init_rwsem);
/*
* 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 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)
{
struct rwsem_waiter *waiter;
struct task_struct *tsk;
int woken;
waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
if (!wakewrite) {
if (waiter->flags & RWSEM_WAITING_FOR_WRITE)
goto out;
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 (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 */
smp_mb();
waiter->task = NULL;
wake_up_process(tsk);
put_task_struct(tsk);
goto out;
}
/* 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) {
struct list_head *next = waiter->list.next;
list_del(&waiter->list);
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);
}
sem->activity += woken;
out:
return sem;
}
/*
* wake a single writer
*/
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);
list_del(&waiter->list);
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 __sched __down_read(struct rw_semaphore *sem)
{
struct rwsem_waiter waiter;
struct task_struct *tsk;
unsigned long flags;
spin_lock_irqsave(&sem->wait_lock, flags);
if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
/* granted */
sem->activity++;
spin_unlock_irqrestore(&sem->wait_lock, flags);
goto out;
}
tsk = current;
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);
/* we don't need to touch the semaphore struct anymore */
spin_unlock_irqrestore(&sem->wait_lock, flags);
/* wait to be given the lock */
for (;;) {
if (!waiter.task)
break;
schedule();
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
}
tsk->state = TASK_RUNNING;
out:
;
}
/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
int __down_read_trylock(struct rw_semaphore *sem)
{
unsigned long flags;
int ret = 0;
spin_lock_irqsave(&sem->wait_lock, flags);
if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
/* granted */
sem->activity++;
ret = 1;
}
spin_unlock_irqrestore(&sem->wait_lock, flags);
return ret;
}
/*
* get a write lock on the semaphore
* - we increment the waiting count anyway to indicate an exclusive lock
*/
void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
{
struct rwsem_waiter waiter;
struct task_struct *tsk;
unsigned long flags;
spin_lock_irqsave(&sem->wait_lock, flags);
if (sem->activity == 0 && list_empty(&sem->wait_list)) {
/* granted */
sem->activity = -1;
spin_unlock_irqrestore(&sem->wait_lock, flags);
goto out;
}
tsk = current;
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);
/* we don't need to touch the semaphore struct anymore */
spin_unlock_irqrestore(&sem->wait_lock, flags);
/* wait to be given the lock */
for (;;) {
if (!waiter.task)
break;
schedule();
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
}
tsk->state = TASK_RUNNING;
out:
;
}
void __sched __down_write(struct rw_semaphore *sem)
{
__down_write_nested(sem, 0);
}
/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
int __down_write_trylock(struct rw_semaphore *sem)
{
unsigned long flags;
int ret = 0;
spin_lock_irqsave(&sem->wait_lock, flags);
if (sem->activity == 0 && list_empty(&sem->wait_list)) {
/* granted */
sem->activity = -1;
ret = 1;
}
spin_unlock_irqrestore(&sem->wait_lock, flags);
return ret;
}
/*
* release a read lock on the semaphore
*/
void __up_read(struct rw_semaphore *sem)
{
unsigned long flags;
spin_lock_irqsave(&sem->wait_lock, flags);
if (--sem->activity == 0 && !list_empty(&sem->wait_list))
sem = __rwsem_wake_one_writer(sem);
spin_unlock_irqrestore(&sem->wait_lock, flags);
}
/*
* release a write lock on the semaphore
*/
void __up_write(struct rw_semaphore *sem)
{
unsigned long flags;
spin_lock_irqsave(&sem->wait_lock, flags);
sem->activity = 0;
if (!list_empty(&sem->wait_list))
sem = __rwsem_do_wake(sem, 1);
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 __downgrade_write(struct rw_semaphore *sem)
{
unsigned long flags;
spin_lock_irqsave(&sem->wait_lock, flags);
sem->activity = 1;
if (!list_empty(&sem->wait_list))
sem = __rwsem_do_wake(sem, 0);
spin_unlock_irqrestore(&sem->wait_lock, flags);
}
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