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/sunrpc/clnt.h>
#include <linux/sunrpc/xprt.h>

#ifdef RPC_DEBUG
#define RPCDBG_FACILITY		RPCDBG_SCHED
#define RPC_TASK_MAGIC_ID	0xf00baa
static int			rpc_task_id;
#endif

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

static void			__rpc_default_timer(struct rpc_task *task);
static void			rpciod_killall(void);
static void			rpc_free(struct rpc_task *task);

static void			rpc_async_schedule(void *);

/*
 * RPC tasks that create another task (e.g. for contacting the portmapper)
 * will wait on this queue for their child's completion
 */
static RPC_WAITQ(childq, "childq");

/*
 * RPC tasks sit here while waiting for conditions to improve.
 */
static RPC_WAITQ(delay_queue, "delayq");

/*
 * All RPC tasks are linked into this list
 */
static LIST_HEAD(all_tasks);

/*
 * rpciod-related stuff
 */
static DECLARE_MUTEX(rpciod_sema);
static unsigned int		rpciod_users;
static struct workqueue_struct *rpciod_workqueue;

/*
 * Spinlock for other critical sections of code.
 */
static DEFINE_SPINLOCK(rpc_sched_lock);

/*
 * 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 inline void
__rpc_disable_timer(struct rpc_task *task)
{
	dprintk("RPC: %4d disabling timer\n", task->tk_pid);
	task->tk_timeout_fn = NULL;
	task->tk_timeout = 0;
}

/*
 * Run a timeout function.
 * We use the callback in order to allow __rpc_wake_up_task()
 * and friends to disable the timer synchronously on SMP systems
 * without calling del_timer_sync(). The latter could cause a
 * deadlock if called while we're holding spinlocks...
 */
static void rpc_run_timer(struct rpc_task *task)
{
	void (*callback)(struct rpc_task *);

	callback = task->tk_timeout_fn;
	task->tk_timeout_fn = NULL;
	if (callback && RPC_IS_QUEUED(task)) {
		dprintk("RPC: %4d running timer\n", task->tk_pid);
		callback(task);
	}
	smp_mb__before_clear_bit();
	clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate);
	smp_mb__after_clear_bit();
}

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

	dprintk("RPC: %4d setting alarm for %lu ms\n",
			task->tk_pid, task->tk_timeout * 1000 / HZ);

	if (timer)
		task->tk_timeout_fn = timer;
	else
		task->tk_timeout_fn = __rpc_default_timer;
	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: %4d 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(