signal.o sys.o kmod.o workqueue.o pid.o task_work.o \
extable.o params.o posix-timers.o \
kthread.o sys_ni.o posix-cpu-timers.o \
- hrtimer.o rwsem.o nsproxy.o \
+ hrtimer.o nsproxy.o \
notifier.o ksysfs.o cred.o reboot.o \
async.o range.o groups.o lglock.o smpboot.o
-obj-y += mutex.o semaphore.o
+obj-y += mutex.o semaphore.o rwsem.o
ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_lockdep.o = -pg
obj-$(CONFIG_RT_MUTEX_TESTER) += rtmutex-tester.o
obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
+obj-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
+obj-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem-xadd.o
\ No newline at end of file
--- /dev/null
+/* 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/export.h>
+
+enum rwsem_waiter_type {
+ RWSEM_WAITING_FOR_WRITE,
+ RWSEM_WAITING_FOR_READ
+};
+
+struct rwsem_waiter {
+ struct list_head list;
+ struct task_struct *task;
+ enum rwsem_waiter_type type;
+};
+
+int rwsem_is_locked(struct rw_semaphore *sem)
+{
+ 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;
+}
+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;
+ raw_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 (waiter->type == RWSEM_WAITING_FOR_WRITE) {
+ if (wakewrite)
+ /* Wake up a writer. Note that we do not grant it the
+ * lock - it will have to acquire it when it runs. */
+ wake_up_process(waiter->task);
+ goto out;
+ }
+
+ /* grant an infinite number of read locks to the front of the queue */
+ woken = 0;
+ do {
+ 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 (next == &sem->wait_list)
+ break;
+ waiter = list_entry(next, struct rwsem_waiter, list);
+ } while (waiter->type != RWSEM_WAITING_FOR_WRITE);
+
+ 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;
+
+ waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
+ wake_up_process(waiter->task);
+
+ 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;
+
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
+ /* granted */
+ sem->activity++;
+ raw_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.type = 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 */
+ raw_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;
+
+
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
+ /* granted */
+ sem->activity++;
+ ret = 1;
+ }
+
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
+
+ return ret;
+}
+
+/*
+ * get a write lock on the semaphore
+ */
+void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
+{
+ struct rwsem_waiter waiter;
+ struct task_struct *tsk;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ /* set up my own style of waitqueue */
+ tsk = current;
+ waiter.task = tsk;
+ waiter.type = RWSEM_WAITING_FOR_WRITE;
+ list_add_tail(&waiter.list, &sem->wait_list);
+
+ /* wait for someone to release the lock */
+ for (;;) {
+ /*
+ * That is the key to support write lock stealing: allows the
+ * task already on CPU to get the lock soon rather than put
+ * itself into sleep and waiting for system woke it or someone
+ * else in the head of the wait list up.
+ */
+ if (sem->activity == 0)
+ break;
+ set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
+ schedule();
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+ }
+ /* got the lock */
+ sem->activity = -1;
+ list_del(&waiter.list);
+
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
+}
+
+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;
+
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ if (sem->activity == 0) {
+ /* got the lock */
+ sem->activity = -1;
+ ret = 1;
+ }
+
+ raw_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;
+
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ if (--sem->activity == 0 && !list_empty(&sem->wait_list))
+ sem = __rwsem_wake_one_writer(sem);
+
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
+}
+
+/*
+ * release a write lock on the semaphore
+ */
+void __up_write(struct rw_semaphore *sem)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ sem->activity = 0;
+ if (!list_empty(&sem->wait_list))
+ sem = __rwsem_do_wake(sem, 1);
+
+ 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 __downgrade_write(struct rw_semaphore *sem)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ sem->activity = 1;
+ if (!list_empty(&sem->wait_list))
+ sem = __rwsem_do_wake(sem, 0);
+
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
+}
+
--- /dev/null
+/* rwsem.c: R/W semaphores: contention handling functions
+ *
+ * Written by David Howells (dhowells@redhat.com).
+ * Derived from arch/i386/kernel/semaphore.c
+ *
+ * Writer lock-stealing by Alex Shi <alex.shi@intel.com>
+ * and Michel Lespinasse <walken@google.com>
+ */
+#include <linux/rwsem.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/export.h>
+
+/*
+ * Initialize an rwsem:
+ */
+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->count = RWSEM_UNLOCKED_VALUE;
+ raw_spin_lock_init(&sem->wait_lock);
+ INIT_LIST_HEAD(&sem->wait_list);
+}
+
+EXPORT_SYMBOL(__init_rwsem);
+
+enum rwsem_waiter_type {
+ RWSEM_WAITING_FOR_WRITE,
+ RWSEM_WAITING_FOR_READ
+};
+
+struct rwsem_waiter {
+ struct list_head list;
+ struct task_struct *task;
+ enum rwsem_waiter_type type;
+};
+
+enum rwsem_wake_type {
+ RWSEM_WAKE_ANY, /* Wake whatever's at head of wait list */
+ RWSEM_WAKE_READERS, /* Wake readers only */
+ RWSEM_WAKE_READ_OWNED /* Waker thread holds the read lock */
+};
+
+/*
+ * handle the lock release when processes blocked on it that can now run
+ * - if we come here from up_xxxx(), then:
+ * - the 'active part' of count (&0x0000ffff) reached 0 (but may have changed)
+ * - the 'waiting part' of count (&0xffff0000) is -ve (and will still be so)
+ * - there must be someone on the queue
+ * - 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 downgrading is false
+ */
+static struct rw_semaphore *
+__rwsem_do_wake(struct rw_semaphore *sem, enum rwsem_wake_type wake_type)
+{
+ struct rwsem_waiter *waiter;
+ struct task_struct *tsk;
+ struct list_head *next;
+ long oldcount, woken, loop, adjustment;
+
+ waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
+ if (waiter->type == RWSEM_WAITING_FOR_WRITE) {
+ if (wake_type == RWSEM_WAKE_ANY)
+ /* Wake writer at the front of the queue, but do not
+ * grant it the lock yet as we want other writers
+ * to be able to steal it. Readers, on the other hand,
+ * will block as they will notice the queued writer.
+ */
+ wake_up_process(waiter->task);
+ goto out;
+ }
+
+ /* Writers might steal the lock before we grant it to the next reader.
+ * We prefer to do the first reader grant before counting readers
+ * so we can bail out early if a writer stole the lock.
+ */
+ adjustment = 0;
+ if (wake_type != RWSEM_WAKE_READ_OWNED) {
+ adjustment = RWSEM_ACTIVE_READ_BIAS;
+ try_reader_grant:
+ oldcount = rwsem_atomic_update(adjustment, sem) - adjustment;
+ if (unlikely(oldcount < RWSEM_WAITING_BIAS)) {
+ /* A writer stole the lock. Undo our reader grant. */
+ if (rwsem_atomic_update(-adjustment, sem) &
+ RWSEM_ACTIVE_MASK)
+ goto out;
+ /* Last active locker left. Retry waking readers. */
+ goto try_reader_grant;
+ }
+ }
+
+ /* Grant an infinite number of read locks to the readers at the front
+ * of the queue. Note we increment the 'active part' of the count by
+ * the number of readers before waking any processes up.
+ */
+ woken = 0;
+ do {
+ woken++;
+
+ if (waiter->list.next == &sem->wait_list)
+ break;
+
+ waiter = list_entry(waiter->list.next,
+ struct rwsem_waiter, list);
+
+ } while (waiter->type != RWSEM_WAITING_FOR_WRITE);
+
+ adjustment = woken * RWSEM_ACTIVE_READ_BIAS - adjustment;
+ if (waiter->type != RWSEM_WAITING_FOR_WRITE)
+ /* hit end of list above */
+ adjustment -= RWSEM_WAITING_BIAS;
+
+ if (adjustment)
+ rwsem_atomic_add(adjustment, sem);
+
+ next = sem->wait_list.next;
+ loop = woken;
+ do {
+ waiter = list_entry(next, struct rwsem_waiter, list);
+ next = waiter->list.next;
+ tsk = waiter->task;
+ smp_mb();
+ waiter->task = NULL;
+ wake_up_process(tsk);
+ put_task_struct(tsk);
+ } while (--loop);
+
+ sem->wait_list.next = next;
+ next->prev = &sem->wait_list;
+
+ out:
+ return sem;
+}
+
+/*
+ * wait for the read lock to be granted
+ */
+struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
+{
+ long count, adjustment = -RWSEM_ACTIVE_READ_BIAS;
+ struct rwsem_waiter waiter;
+ struct task_struct *tsk = current;
+
+ /* set up my own style of waitqueue */
+ waiter.task = tsk;
+ waiter.type = RWSEM_WAITING_FOR_READ;
+ get_task_struct(tsk);
+
+ raw_spin_lock_irq(&sem->wait_lock);
+ if (list_empty(&sem->wait_list))
+ adjustment += RWSEM_WAITING_BIAS;
+ list_add_tail(&waiter.list, &sem->wait_list);
+
+ /* we're now waiting on the lock, but no longer actively locking */
+ count = rwsem_atomic_update(adjustment, sem);
+
+ /* If there are no active locks, wake the front queued process(es).
+ *
+ * If there are no writers and we are first in the queue,
+ * wake our own waiter to join the existing active readers !
+ */
+ if (count == RWSEM_WAITING_BIAS ||
+ (count > RWSEM_WAITING_BIAS &&
+ adjustment != -RWSEM_ACTIVE_READ_BIAS))
+ sem = __rwsem_do_wake(sem, RWSEM_WAKE_ANY);
+
+ raw_spin_unlock_irq(&sem->wait_lock);
+
+ /* wait to be given the lock */
+ while (true) {
+ set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+ if (!waiter.task)
+ break;
+ schedule();
+ }
+
+ tsk->state = TASK_RUNNING;
+
+ return sem;
+}
+
+/*
+ * wait until we successfully acquire the write lock
+ */
+struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
+{
+ long count, adjustment = -RWSEM_ACTIVE_WRITE_BIAS;
+ struct rwsem_waiter waiter;
+ struct task_struct *tsk = current;
+
+ /* set up my own style of waitqueue */
+ waiter.task = tsk;
+ waiter.type = RWSEM_WAITING_FOR_WRITE;
+
+ raw_spin_lock_irq(&sem->wait_lock);
+ if (list_empty(&sem->wait_list))
+ adjustment += RWSEM_WAITING_BIAS;
+ list_add_tail(&waiter.list, &sem->wait_list);
+
+ /* we're now waiting on the lock, but no longer actively locking */
+ count = rwsem_atomic_update(adjustment, sem);
+
+ /* If there were already threads queued before us and there are no
+ * active writers, the lock must be read owned; so we try to wake
+ * any read locks that were queued ahead of us. */
+ if (count > RWSEM_WAITING_BIAS &&
+ adjustment == -RWSEM_ACTIVE_WRITE_BIAS)
+ sem = __rwsem_do_wake(sem, RWSEM_WAKE_READERS);
+
+ /* wait until we successfully acquire the lock */
+ set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+ while (true) {
+ if (!(count & RWSEM_ACTIVE_MASK)) {
+ /* Try acquiring the write lock. */
+ count = RWSEM_ACTIVE_WRITE_BIAS;
+ if (!list_is_singular(&sem->wait_list))
+ count += RWSEM_WAITING_BIAS;
+
+ if (sem->count == RWSEM_WAITING_BIAS &&
+ cmpxchg(&sem->count, RWSEM_WAITING_BIAS, count) ==
+ RWSEM_WAITING_BIAS)
+ break;
+ }
+
+ raw_spin_unlock_irq(&sem->wait_lock);
+
+ /* Block until there are no active lockers. */
+ do {
+ schedule();
+ set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+ } while ((count = sem->count) & RWSEM_ACTIVE_MASK);
+
+ raw_spin_lock_irq(&sem->wait_lock);
+ }
+
+ list_del(&waiter.list);
+ raw_spin_unlock_irq(&sem->wait_lock);
+ tsk->state = TASK_RUNNING;
+
+ return sem;
+}
+
+/*
+ * handle waking up a waiter on the semaphore
+ * - up_read/up_write has decremented the active part of count if we come here
+ */
+struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ /* do nothing if list empty */
+ if (!list_empty(&sem->wait_list))
+ sem = __rwsem_do_wake(sem, RWSEM_WAKE_ANY);
+
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
+
+ return sem;
+}
+
+/*
+ * downgrade a write lock into a read lock
+ * - caller incremented waiting part of count and discovered it still negative
+ * - just wake up any readers at the front of the queue
+ */
+struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&sem->wait_lock, flags);
+
+ /* do nothing if list empty */
+ if (!list_empty(&sem->wait_list))
+ sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED);
+
+ raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
+
+ return sem;
+}
+
+EXPORT_SYMBOL(rwsem_down_read_failed);
+EXPORT_SYMBOL(rwsem_down_write_failed);
+EXPORT_SYMBOL(rwsem_wake);
+EXPORT_SYMBOL(rwsem_downgrade_wake);
--- /dev/null
+/* 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/export.h>
+#include <linux/rwsem.h>
+
+#include <linux/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_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
+{
+ might_sleep();
+ rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
+
+ LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
+}
+
+EXPORT_SYMBOL(_down_write_nest_lock);
+
+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
+
+
+++ /dev/null
-/* 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/export.h>
-#include <linux/rwsem.h>
-
-#include <linux/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_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
-{
- might_sleep();
- rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
-
- LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
-}
-
-EXPORT_SYMBOL(_down_write_nest_lock);
-
-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
-
-
obj-$(CONFIG_HAS_IOMEM) += iomap_copy.o devres.o
obj-$(CONFIG_CHECK_SIGNATURE) += check_signature.o
obj-$(CONFIG_DEBUG_LOCKING_API_SELFTESTS) += locking-selftest.o
-lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
-lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
lib-$(CONFIG_PERCPU_RWSEM) += percpu-rwsem.o
CFLAGS_hweight.o = $(subst $(quote),,$(CONFIG_ARCH_HWEIGHT_CFLAGS))
+++ /dev/null
-/* 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/export.h>
-
-enum rwsem_waiter_type {
- RWSEM_WAITING_FOR_WRITE,
- RWSEM_WAITING_FOR_READ
-};
-
-struct rwsem_waiter {
- struct list_head list;
- struct task_struct *task;
- enum rwsem_waiter_type type;
-};
-
-int rwsem_is_locked(struct rw_semaphore *sem)
-{
- 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;
-}
-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;
- raw_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 (waiter->type == RWSEM_WAITING_FOR_WRITE) {
- if (wakewrite)
- /* Wake up a writer. Note that we do not grant it the
- * lock - it will have to acquire it when it runs. */
- wake_up_process(waiter->task);
- goto out;
- }
-
- /* grant an infinite number of read locks to the front of the queue */
- woken = 0;
- do {
- 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 (next == &sem->wait_list)
- break;
- waiter = list_entry(next, struct rwsem_waiter, list);
- } while (waiter->type != RWSEM_WAITING_FOR_WRITE);
-
- 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;
-
- waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
- wake_up_process(waiter->task);
-
- 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;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
- /* granted */
- sem->activity++;
- raw_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.type = 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 */
- raw_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;
-
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
- /* granted */
- sem->activity++;
- ret = 1;
- }
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-
- return ret;
-}
-
-/*
- * get a write lock on the semaphore
- */
-void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
-{
- struct rwsem_waiter waiter;
- struct task_struct *tsk;
- unsigned long flags;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- /* set up my own style of waitqueue */
- tsk = current;
- waiter.task = tsk;
- waiter.type = RWSEM_WAITING_FOR_WRITE;
- list_add_tail(&waiter.list, &sem->wait_list);
-
- /* wait for someone to release the lock */
- for (;;) {
- /*
- * That is the key to support write lock stealing: allows the
- * task already on CPU to get the lock soon rather than put
- * itself into sleep and waiting for system woke it or someone
- * else in the head of the wait list up.
- */
- if (sem->activity == 0)
- break;
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
- schedule();
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
- }
- /* got the lock */
- sem->activity = -1;
- list_del(&waiter.list);
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-}
-
-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;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- if (sem->activity == 0) {
- /* got the lock */
- sem->activity = -1;
- ret = 1;
- }
-
- raw_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;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- if (--sem->activity == 0 && !list_empty(&sem->wait_list))
- sem = __rwsem_wake_one_writer(sem);
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-}
-
-/*
- * release a write lock on the semaphore
- */
-void __up_write(struct rw_semaphore *sem)
-{
- unsigned long flags;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- sem->activity = 0;
- if (!list_empty(&sem->wait_list))
- sem = __rwsem_do_wake(sem, 1);
-
- 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 __downgrade_write(struct rw_semaphore *sem)
-{
- unsigned long flags;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- sem->activity = 1;
- if (!list_empty(&sem->wait_list))
- sem = __rwsem_do_wake(sem, 0);
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-}
-
+++ /dev/null
-/* rwsem.c: R/W semaphores: contention handling functions
- *
- * Written by David Howells (dhowells@redhat.com).
- * Derived from arch/i386/kernel/semaphore.c
- *
- * Writer lock-stealing by Alex Shi <alex.shi@intel.com>
- * and Michel Lespinasse <walken@google.com>
- */
-#include <linux/rwsem.h>
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <linux/export.h>
-
-/*
- * Initialize an rwsem:
- */
-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->count = RWSEM_UNLOCKED_VALUE;
- raw_spin_lock_init(&sem->wait_lock);
- INIT_LIST_HEAD(&sem->wait_list);
-}
-
-EXPORT_SYMBOL(__init_rwsem);
-
-enum rwsem_waiter_type {
- RWSEM_WAITING_FOR_WRITE,
- RWSEM_WAITING_FOR_READ
-};
-
-struct rwsem_waiter {
- struct list_head list;
- struct task_struct *task;
- enum rwsem_waiter_type type;
-};
-
-enum rwsem_wake_type {
- RWSEM_WAKE_ANY, /* Wake whatever's at head of wait list */
- RWSEM_WAKE_READERS, /* Wake readers only */
- RWSEM_WAKE_READ_OWNED /* Waker thread holds the read lock */
-};
-
-/*
- * handle the lock release when processes blocked on it that can now run
- * - if we come here from up_xxxx(), then:
- * - the 'active part' of count (&0x0000ffff) reached 0 (but may have changed)
- * - the 'waiting part' of count (&0xffff0000) is -ve (and will still be so)
- * - there must be someone on the queue
- * - 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 downgrading is false
- */
-static struct rw_semaphore *
-__rwsem_do_wake(struct rw_semaphore *sem, enum rwsem_wake_type wake_type)
-{
- struct rwsem_waiter *waiter;
- struct task_struct *tsk;
- struct list_head *next;
- long oldcount, woken, loop, adjustment;
-
- waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
- if (waiter->type == RWSEM_WAITING_FOR_WRITE) {
- if (wake_type == RWSEM_WAKE_ANY)
- /* Wake writer at the front of the queue, but do not
- * grant it the lock yet as we want other writers
- * to be able to steal it. Readers, on the other hand,
- * will block as they will notice the queued writer.
- */
- wake_up_process(waiter->task);
- goto out;
- }
-
- /* Writers might steal the lock before we grant it to the next reader.
- * We prefer to do the first reader grant before counting readers
- * so we can bail out early if a writer stole the lock.
- */
- adjustment = 0;
- if (wake_type != RWSEM_WAKE_READ_OWNED) {
- adjustment = RWSEM_ACTIVE_READ_BIAS;
- try_reader_grant:
- oldcount = rwsem_atomic_update(adjustment, sem) - adjustment;
- if (unlikely(oldcount < RWSEM_WAITING_BIAS)) {
- /* A writer stole the lock. Undo our reader grant. */
- if (rwsem_atomic_update(-adjustment, sem) &
- RWSEM_ACTIVE_MASK)
- goto out;
- /* Last active locker left. Retry waking readers. */
- goto try_reader_grant;
- }
- }
-
- /* Grant an infinite number of read locks to the readers at the front
- * of the queue. Note we increment the 'active part' of the count by
- * the number of readers before waking any processes up.
- */
- woken = 0;
- do {
- woken++;
-
- if (waiter->list.next == &sem->wait_list)
- break;
-
- waiter = list_entry(waiter->list.next,
- struct rwsem_waiter, list);
-
- } while (waiter->type != RWSEM_WAITING_FOR_WRITE);
-
- adjustment = woken * RWSEM_ACTIVE_READ_BIAS - adjustment;
- if (waiter->type != RWSEM_WAITING_FOR_WRITE)
- /* hit end of list above */
- adjustment -= RWSEM_WAITING_BIAS;
-
- if (adjustment)
- rwsem_atomic_add(adjustment, sem);
-
- next = sem->wait_list.next;
- loop = woken;
- do {
- waiter = list_entry(next, struct rwsem_waiter, list);
- next = waiter->list.next;
- tsk = waiter->task;
- smp_mb();
- waiter->task = NULL;
- wake_up_process(tsk);
- put_task_struct(tsk);
- } while (--loop);
-
- sem->wait_list.next = next;
- next->prev = &sem->wait_list;
-
- out:
- return sem;
-}
-
-/*
- * wait for the read lock to be granted
- */
-struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
-{
- long count, adjustment = -RWSEM_ACTIVE_READ_BIAS;
- struct rwsem_waiter waiter;
- struct task_struct *tsk = current;
-
- /* set up my own style of waitqueue */
- waiter.task = tsk;
- waiter.type = RWSEM_WAITING_FOR_READ;
- get_task_struct(tsk);
-
- raw_spin_lock_irq(&sem->wait_lock);
- if (list_empty(&sem->wait_list))
- adjustment += RWSEM_WAITING_BIAS;
- list_add_tail(&waiter.list, &sem->wait_list);
-
- /* we're now waiting on the lock, but no longer actively locking */
- count = rwsem_atomic_update(adjustment, sem);
-
- /* If there are no active locks, wake the front queued process(es).
- *
- * If there are no writers and we are first in the queue,
- * wake our own waiter to join the existing active readers !
- */
- if (count == RWSEM_WAITING_BIAS ||
- (count > RWSEM_WAITING_BIAS &&
- adjustment != -RWSEM_ACTIVE_READ_BIAS))
- sem = __rwsem_do_wake(sem, RWSEM_WAKE_ANY);
-
- raw_spin_unlock_irq(&sem->wait_lock);
-
- /* wait to be given the lock */
- while (true) {
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
- if (!waiter.task)
- break;
- schedule();
- }
-
- tsk->state = TASK_RUNNING;
-
- return sem;
-}
-
-/*
- * wait until we successfully acquire the write lock
- */
-struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
-{
- long count, adjustment = -RWSEM_ACTIVE_WRITE_BIAS;
- struct rwsem_waiter waiter;
- struct task_struct *tsk = current;
-
- /* set up my own style of waitqueue */
- waiter.task = tsk;
- waiter.type = RWSEM_WAITING_FOR_WRITE;
-
- raw_spin_lock_irq(&sem->wait_lock);
- if (list_empty(&sem->wait_list))
- adjustment += RWSEM_WAITING_BIAS;
- list_add_tail(&waiter.list, &sem->wait_list);
-
- /* we're now waiting on the lock, but no longer actively locking */
- count = rwsem_atomic_update(adjustment, sem);
-
- /* If there were already threads queued before us and there are no
- * active writers, the lock must be read owned; so we try to wake
- * any read locks that were queued ahead of us. */
- if (count > RWSEM_WAITING_BIAS &&
- adjustment == -RWSEM_ACTIVE_WRITE_BIAS)
- sem = __rwsem_do_wake(sem, RWSEM_WAKE_READERS);
-
- /* wait until we successfully acquire the lock */
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
- while (true) {
- if (!(count & RWSEM_ACTIVE_MASK)) {
- /* Try acquiring the write lock. */
- count = RWSEM_ACTIVE_WRITE_BIAS;
- if (!list_is_singular(&sem->wait_list))
- count += RWSEM_WAITING_BIAS;
-
- if (sem->count == RWSEM_WAITING_BIAS &&
- cmpxchg(&sem->count, RWSEM_WAITING_BIAS, count) ==
- RWSEM_WAITING_BIAS)
- break;
- }
-
- raw_spin_unlock_irq(&sem->wait_lock);
-
- /* Block until there are no active lockers. */
- do {
- schedule();
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
- } while ((count = sem->count) & RWSEM_ACTIVE_MASK);
-
- raw_spin_lock_irq(&sem->wait_lock);
- }
-
- list_del(&waiter.list);
- raw_spin_unlock_irq(&sem->wait_lock);
- tsk->state = TASK_RUNNING;
-
- return sem;
-}
-
-/*
- * handle waking up a waiter on the semaphore
- * - up_read/up_write has decremented the active part of count if we come here
- */
-struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem)
-{
- unsigned long flags;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- /* do nothing if list empty */
- if (!list_empty(&sem->wait_list))
- sem = __rwsem_do_wake(sem, RWSEM_WAKE_ANY);
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-
- return sem;
-}
-
-/*
- * downgrade a write lock into a read lock
- * - caller incremented waiting part of count and discovered it still negative
- * - just wake up any readers at the front of the queue
- */
-struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
-{
- unsigned long flags;
-
- raw_spin_lock_irqsave(&sem->wait_lock, flags);
-
- /* do nothing if list empty */
- if (!list_empty(&sem->wait_list))
- sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED);
-
- raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
-
- return sem;
-}
-
-EXPORT_SYMBOL(rwsem_down_read_failed);
-EXPORT_SYMBOL(rwsem_down_write_failed);
-EXPORT_SYMBOL(rwsem_wake);
-EXPORT_SYMBOL(rwsem_downgrade_wake);
projects / cascardo / linux.git / commitdiff