path: root/net/sunrpc/sched.c

/*
 * linux/net/sunrpc/sched.c
 *
 * Scheduling for synchronous and asynchronous RPC requests.
 *
 * Copyright (C) 1996 Olaf Kirch, <okir@monad.swb.de>
 *
 * TCP NFS related read + write fixes
 * (C) 1999 Dave Airlie, University of Limerick, Ireland <airlied@linux.ie>
 */

#include <linux/module.h>

#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/mempool.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>

#include <linux/sunrpc/clnt.h>

#ifdef RPC_DEBUG
#define RPCDBG_FACILITY		RPCDBG_SCHED
#define RPC_TASK_MAGIC_ID	0xf00baa
#endif

/*
 * RPC slabs and memory pools
 */
#define RPC_BUFFER_MAXSIZE	(2048)
#define RPC_BUFFER_POOLSIZE	(8)
#define RPC_TASK_POOLSIZE	(8)
static struct kmem_cache	*rpc_task_slabp __read_mostly;
static struct kmem_cache	*rpc_buffer_slabp __read_mostly;
static mempool_t	*rpc_task_mempool __read_mostly;
static mempool_t	*rpc_buffer_mempool __read_mostly;

static void			rpc_async_schedule(struct work_struct *);
static void			 rpc_release_task(struct rpc_task *task);

/*
 * RPC tasks sit here while waiting for conditions to improve.
 */
static struct rpc_wait_queue delay_queue;

/*
 * rpciod-related stuff
 */
struct workqueue_struct *rpciod_workqueue;

/*
 * Disable the timer for a given RPC task. Should be called with
 * queue->lock and bh_disabled in order to avoid races within
 * rpc_run_timer().
 */
static void
__rpc_disable_timer(struct rpc_task *task)
{
	dprintk("RPC: %5u disabling timer\n", task->tk_pid);
	task->tk_timeout = 0;
}

/*
 * Set up a timer for the current task.
 */
static void
__rpc_add_timer(struct rpc_task *task)
{
	if (!task->tk_timeout)
		return;

	dprintk("RPC: %5u setting alarm for %lu ms\n",
			task->tk_pid, task->tk_timeout * 1000 / HZ);

	set_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate);
	mod_timer(&task->tk_timer, jiffies + task->tk_timeout);
}

/*
 * Delete any timer for the current task. Because we use del_timer_sync(),
 * this function should never be called while holding queue->lock.
 */
static void
rpc_delete_timer(struct rpc_task *task)
{
	if (RPC_IS_QUEUED(task))
		return;
	if (test_and_clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate)) {
		del_singleshot_timer_sync(&task->tk_timer);
		dprintk("RPC: %5u deleting timer\n", task->tk_pid);
	}
}

/*
 * Add new request to a priority queue.
 */
static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue, struct rpc_task *task)
{
	struct list_head *q;
	struct rpc_task *t;

	INIT_LIST_HEAD(&task->u.tk_wait.links);
	q = &queue->tasks[task->tk_priority];
	if (unlikely(task->tk_priority > queue->maxpriority))
		q = &queue->tasks[queue->maxpriority];
	list_for_each_entry(t, q, u.tk_wait.list) {
		if (t->tk_owner == task->tk_owner) {
			list_add_tail(&task->u.tk_wait.list, &t->u.tk_wait.links);
			return;
		}
	}
	list_add_tail(&task->u.tk_wait.list, q);
}

/*
 * Add new request to wait queue.
 *
 * Swapper tasks always get inserted at the head of the queue.
 * This should avoid many nasty memory deadlocks and hopefully
 * improve overall performance.
 * Everyone else gets appended to the queue to ensure proper FIFO behavior.
 */
static void __rpc_add_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
{
	BUG_ON (RPC_IS_QUEUED(task));

	if (RPC_IS_PRIORITY(queue))
		__rpc_add_wait_queue_priority(queue, task);
	else if (RPC_IS_SWAPPER(task))
		list_add(&task->u.tk_wait.list, &queue->tasks[0]);
	else
		list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
	task->tk_waitqueue = queue;
	queue->qlen++;
	rpc_set_queued(task);

	dprintk("RPC: %5u added to queue %p \"%s\"\n",
			task->tk_pid, queue, rpc_qname(queue));
}

/*
 * Remove request from a priority queue.
 */
static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
{
	struct rpc_task *t;

	if (!list_empty(&task->u.tk_wait.links)) {
		t = list_entry(task->u.tk_wait.links.next, struct rpc_task, u.