sched: Move wait.c into kernel/sched/

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-5q5yqvdaen0rmapwloeaotx3@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 402 insertions, 0 deletions

diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 54adcf35f495..f8d3f4baa1a1 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -12,6 +12,7 @@ CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
 endif
 
 obj-y += core.o proc.o clock.o cputime.o idle_task.o fair.o rt.o stop_task.o
+obj-y += wait.o
 obj-$(CONFIG_SMP) += cpupri.o
 obj-$(CONFIG_SCHED_AUTOGROUP) += auto_group.o
 obj-$(CONFIG_SCHEDSTATS) += stats.o
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
new file mode 100644
index 000000000000..de21c6305a44
--- /dev/null
+++ b/kernel/sched/wait.c
@@ -0,0 +1,401 @@
+/*
+ * Generic waiting primitives.
+ *
+ * (C) 2004 Nadia Yvette Chambers, Oracle
+ */
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/wait.h>
+#include <linux/hash.h>
+
+void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *key)
+{
+        spin_lock_init(&q->lock);
+        lockdep_set_class_and_name(&q->lock, key, name);
+        INIT_LIST_HEAD(&q->task_list);
+}
+
+EXPORT_SYMBOL(__init_waitqueue_head);
+
+void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
+{
+        unsigned long flags;
+
+        wait->flags &= ~WQ_FLAG_EXCLUSIVE;
+        spin_lock_irqsave(&q->lock, flags);
+        __add_wait_queue(q, wait);
+        spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(add_wait_queue);
+
+void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait)
+{
+        unsigned long flags;
+
+        wait->flags |= WQ_FLAG_EXCLUSIVE;
+        spin_lock_irqsave(&q->lock, flags);
+        __add_wait_queue_tail(q, wait);
+        spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(add_wait_queue_exclusive);
+
+void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&q->lock, flags);
+        __remove_wait_queue(q, wait);
+        spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(remove_wait_queue);
+
+
+/*
+ * Note: we use "set_current_state()" _after_ the wait-queue add,
+ * because we need a memory barrier there on SMP, so that any
+ * wake-function that tests for the wait-queue being active
+ * will be guaranteed to see waitqueue addition _or_ subsequent
+ * tests in this thread will see the wakeup having taken place.
+ *
+ * The spin_unlock() itself is semi-permeable and only protects
+ * one way (it only protects stuff inside the critical region and
+ * stops them from bleeding out - it would still allow subsequent
+ * loads to move into the critical region).
+ */
+void
+prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
+{
+        unsigned long flags;
+
+        wait->flags &= ~WQ_FLAG_EXCLUSIVE;
+        spin_lock_irqsave(&q->lock, flags);
+        if (list_empty(&wait->task_list))
+                __add_wait_queue(q, wait);
+        set_current_state(state);
+        spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(prepare_to_wait);
+
+void
+prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
+{
+        unsigned long flags;
+
+        wait->flags |= WQ_FLAG_EXCLUSIVE;
+        spin_lock_irqsave(&q->lock, flags);
+        if (list_empty(&wait->task_list))
+                __add_wait_queue_tail(q, wait);
+        set_current_state(state);
+        spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(prepare_to_wait_exclusive);
+
+long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
+{
+        unsigned long flags;
+
+        if (signal_pending_state(state, current))
+                return -ERESTARTSYS;
+
+        wait->private = current;
+        wait->func = autoremove_wake_function;
+
+        spin_lock_irqsave(&q->lock, flags);
+        if (list_empty(&wait->task_list)) {
+                if (wait->flags & WQ_FLAG_EXCLUSIVE)
+                        __add_wait_queue_tail(q, wait);
+                else
+                        __add_wait_queue(q, wait);
+        }
+        set_current_state(state);
+        spin_unlock_irqrestore(&q->lock, flags);
+
+        return 0;
+}
+EXPORT_SYMBOL(prepare_to_wait_event);
+
+/**
+ * finish_wait - clean up after waiting in a queue
+ * @q: waitqueue waited on
+ * @wait: wait descriptor
+ *
+ * Sets current thread back to running state and removes
+ * the wait descriptor from the given waitqueue if still
+ * queued.
+ */
+void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
+{
+        unsigned long flags;
+
+        __set_current_state(TASK_RUNNING);
+        /*
+         * We can check for list emptiness outside the lock
+         * IFF:
+         *  - we use the "careful" check that verifies both
+         *    the next and prev pointers, so that there cannot
+         *    be any half-pending updates in progress on other
+         *    CPU's that we haven't seen yet (and that might
+         *    still change the stack area.
+         * and
+         *  - all other users take the lock (ie we can only
+         *    have _one_ other CPU that looks at or modifies
+         *    the list).
+         */
+        if (!list_empty_careful(&wait->task_list)) {
+                spin_lock_irqsave(&q->lock, flags);
+                list_del_init(&wait->task_list);
+                spin_unlock_irqrestore(&q->lock, flags);
+        }
+}
+EXPORT_SYMBOL(finish_wait);
+
+/**
+ * abort_exclusive_wait - abort exclusive waiting in a queue
+ * @q: waitqueue waited on
+ * @wait: wait descriptor
+ * @mode: runstate of the waiter to be woken
+ * @key: key to identify a wait bit queue or %NULL
+ *
+ * Sets current thread back to running state and removes
+ * the wait descriptor from the given waitqueue if still
+ * queued.
+ *
+ * Wakes up the next waiter if the caller is concurrently
+ * woken up through the queue.
+ *
+ * This prevents waiter starvation where an exclusive waiter
+ * aborts and is woken up concurrently and no one wakes up
+ * the next waiter.
+ */
+void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait,
+                        unsigned int mode, void *key)
+{
+        unsigned long flags;
+
+        __set_current_state(TASK_RUNNING);
+        spin_lock_irqsave(&q->lock, flags);
+        if (!list_empty(&wait->task_list))
+                list_del_init(&wait->task_list);
+        else if (waitqueue_active(q))
+                __wake_up_locked_key(q, mode, key);
+        spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(abort_exclusive_wait);
+
+int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
+{
+        int ret = default_wake_function(wait, mode, sync, key);
+
+        if (ret)
+                list_del_init(&wait->task_list);
+        return ret;
+}
+EXPORT_SYMBOL(autoremove_wake_function);
+
+int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
+{
+        struct wait_bit_key *key = arg;
+        struct wait_bit_queue *wait_bit
+                = container_of(wait, struct wait_bit_queue, wait);
+
+        if (wait_bit->key.flags != key->flags ||
+                        wait_bit->key.bit_nr != key->bit_nr ||
+                        test_bit(key->bit_nr, key->flags))
+                return 0;
+        else
+                return autoremove_wake_function(wait, mode, sync, key);
+}
+EXPORT_SYMBOL(wake_bit_function);
+
+/*
+ * To allow interruptible waiting and asynchronous (i.e. nonblocking)
+ * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
+ * permitted return codes. Nonzero return codes halt waiting and return.
+ */
+int __sched
+__wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
+                        int (*action)(void *), unsigned mode)
+{
+        int ret = 0;
+
+        do {
+                prepare_to_wait(wq, &q->wait, mode);
+                if (test_bit(q->key.bit_nr, q->key.flags))
+                        ret = (*action)(q->key.flags);
+        } while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
+        finish_wait(wq, &q->wait);
+        return ret;
+}
+EXPORT_SYMBOL(__wait_on_bit);
+
+int __sched out_of_line_wait_on_bit(void *word, int bit,
+                                        int (*action)(void *), unsigned mode)
+{
+        wait_queue_head_t *wq = bit_waitqueue(word, bit);
+        DEFINE_WAIT_BIT(wait, word, bit);
+
+        return __wait_on_bit(wq, &wait, action, mode);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_bit);
+
+int __sched
+__wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
+                        int (*action)(void *), unsigned mode)
+{
+        do {
+                int ret;
+
+                prepare_to_wait_exclusive(wq, &q->wait, mode);
+                if (!test_bit(q->key.bit_nr, q->key.flags))
+                        continue;
+                ret = action(q->key.flags);
+                if (!ret)
+                        continue;
+                abort_exclusive_wait(wq, &q->wait, mode, &q->key);
+                return ret;
+        } while (test_and_set_bit(q->key.bit_nr, q->key.flags));
+        finish_wait(wq, &q->wait);
+        return 0;
+}
+EXPORT_SYMBOL(__wait_on_bit_lock);
+
+int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
+                                        int (*action)(void *), unsigned mode)
+{
+        wait_queue_head_t *wq = bit_waitqueue(word, bit);
+        DEFINE_WAIT_BIT(wait, word, bit);
+
+        return __wait_on_bit_lock(wq, &wait, action, mode);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
+
+void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
+{
+        struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
+        if (waitqueue_active(wq))
+                __wake_up(wq, TASK_NORMAL, 1, &key);
+}
+EXPORT_SYMBOL(__wake_up_bit);
+
+/**
+ * wake_up_bit - wake up a waiter on a bit
+ * @word: the word being waited on, a kernel virtual address
+ * @bit: the bit of the word being waited on
+ *
+ * There is a standard hashed waitqueue table for generic use. This
+ * is the part of the hashtable's accessor API that wakes up waiters
+ * on a bit. For instance, if one were to have waiters on a bitflag,
+ * one would call wake_up_bit() after clearing the bit.
+ *
+ * In order for this to function properly, as it uses waitqueue_active()
+ * internally, some kind of memory barrier must be done prior to calling
+ * this. Typically, this will be smp_mb__after_clear_bit(), but in some
+ * cases where bitflags are manipulated non-atomically under a lock, one
+ * may need to use a less regular barrier, such fs/inode.c's smp_mb(),
+ * because spin_unlock() does not guarantee a memory barrier.
+ */
+void wake_up_bit(void *word, int bit)
+{
+        __wake_up_bit(bit_waitqueue(word, bit), word, bit);
+}
+EXPORT_SYMBOL(wake_up_bit);
+
+wait_queue_head_t *bit_waitqueue(void *word, int bit)
+{
+        const int shift = BITS_PER_LONG == 32 ? 5 : 6;
+        const struct zone *zone = page_zone(virt_to_page(word));
+        unsigned long val = (unsigned long)word << shift | bit;
+
+        return &zone->wait_table[hash_long(val, zone->wait_table_bits)];
+}
+EXPORT_SYMBOL(bit_waitqueue);
+
+/*
+ * Manipulate the atomic_t address to produce a better bit waitqueue table hash
+ * index (we're keying off bit -1, but that would produce a horrible hash
+ * value).
+ */
+static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
+{
+        if (BITS_PER_LONG == 64) {
+                unsigned long q = (unsigned long)p;
+                return bit_waitqueue((void *)(q & ~1), q & 1);
+        }
+        return bit_waitqueue(p, 0);
+}
+
+static int wake_atomic_t_function(wait_queue_t *wait, unsigned mode, int sync,
+                                  void *arg)
+{
+        struct wait_bit_key *key = arg;
+        struct wait_bit_queue *wait_bit
+                = container_of(wait, struct wait_bit_queue, wait);
+        atomic_t *val = key->flags;
+
+        if (wait_bit->key.flags != key->flags ||
+            wait_bit->key.bit_nr != key->bit_nr ||
+            atomic_read(val) != 0)
+                return 0;
+        return autoremove_wake_function(wait, mode, sync, key);
+}
+
+/*
+ * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
+ * the actions of __wait_on_atomic_t() are permitted return codes.  Nonzero
+ * return codes halt waiting and return.
+ */
+static __sched
+int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
+                       int (*action)(atomic_t *), unsigned mode)
+{
+        atomic_t *val;
+        int ret = 0;
+
+        do {
+                prepare_to_wait(wq, &q->wait, mode);
+                val = q->key.flags;
+                if (atomic_read(val) == 0)
+                        break;
+                ret = (*action)(val);
+        } while (!ret && atomic_read(val) != 0);
+        finish_wait(wq, &q->wait);
+        return ret;
+}
+
+#define DEFINE_WAIT_ATOMIC_T(name, p)                                   \
+        struct wait_bit_queue name = {                                  \
+                .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p),              \
+                .wait   = {                                             \
+                        .private        = current,                      \
+                        .func           = wake_atomic_t_function,       \
+                        .task_list      =                               \
+                                LIST_HEAD_INIT((name).wait.task_list),  \
+                },                                                      \
+        }
+
+__sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
+                                         unsigned mode)
+{
+        wait_queue_head_t *wq = atomic_t_waitqueue(p);
+        DEFINE_WAIT_ATOMIC_T(wait, p);
+
+        return __wait_on_atomic_t(wq, &wait, action, mode);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
+
+/**
+ * wake_up_atomic_t - Wake up a waiter on a atomic_t
+ * @p: The atomic_t being waited on, a kernel virtual address
+ *
+ * Wake up anyone waiting for the atomic_t to go to zero.
+ *
+ * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
+ * check is done by the waiter's wake function, not the by the waker itself).
+ */
+void wake_up_atomic_t(atomic_t *p)
+{
+        __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
+}
+EXPORT_SYMBOL(wake_up_atomic_t);