1 /* 2 * Copyright (C) 2007 Oracle. All rights reserved. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public 6 * License v2 as published by the Free Software Foundation. 7 * 8 * This program is distributed in the hope that it will be useful, 9 * but WITHOUT ANY WARRANTY; without even the implied warranty of 10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 11 * General Public License for more details. 12 * 13 * You should have received a copy of the GNU General Public 14 * License along with this program; if not, write to the 15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330, 16 * Boston, MA 021110-1307, USA. 17 */ 18 19 #ifndef __BTRFS_ASYNC_THREAD_ 20 #define __BTRFS_ASYNC_THREAD_ 21 22 struct btrfs_worker_thread; 23 24 /* 25 * This is similar to a workqueue, but it is meant to spread the operations 26 * across all available cpus instead of just the CPU that was used to 27 * queue the work. There is also some batching introduced to try and 28 * cut down on context switches. 29 * 30 * By default threads are added on demand up to 2 * the number of cpus. 31 * Changing struct btrfs_workers->max_workers is one way to prevent 32 * demand creation of kthreads. 33 * 34 * the basic model of these worker threads is to embed a btrfs_work 35 * structure in your own data struct, and use container_of in a 36 * work function to get back to your data struct. 37 */ 38 struct btrfs_work { 39 /* 40 * func should be set to the function you want called 41 * your work struct is passed as the only arg 42 * 43 * ordered_func must be set for work sent to an ordered work queue, 44 * and it is called to complete a given work item in the same 45 * order they were sent to the queue. 46 */ 47 void (*func)(struct btrfs_work *work); 48 void (*ordered_func)(struct btrfs_work *work); 49 void (*ordered_free)(struct btrfs_work *work); 50 51 /* 52 * flags should be set to zero. It is used to make sure the 53 * struct is only inserted once into the list. 54 */ 55 unsigned long flags; 56 57 /* don't touch these */ 58 struct btrfs_worker_thread *worker; 59 struct list_head list; 60 struct list_head order_list; 61 }; 62 63 struct btrfs_workers { 64 /* current number of running workers */ 65 int num_workers; 66 67 int num_workers_starting; 68 69 /* max number of workers allowed. changed by btrfs_start_workers */ 70 int max_workers; 71 72 /* once a worker has this many requests or fewer, it is idle */ 73 int idle_thresh; 74 75 /* force completions in the order they were queued */ 76 int ordered; 77 78 /* more workers required, but in an interrupt handler */ 79 int atomic_start_pending; 80 81 /* 82 * are we allowed to sleep while starting workers or are we required 83 * to start them at a later time? If we can't sleep, this indicates 84 * which queue we need to use to schedule thread creation. 85 */ 86 struct btrfs_workers *atomic_worker_start; 87 88 /* list with all the work threads. The workers on the idle thread 89 * may be actively servicing jobs, but they haven't yet hit the 90 * idle thresh limit above. 91 */ 92 struct list_head worker_list; 93 struct list_head idle_list; 94 95 /* 96 * when operating in ordered mode, this maintains the list 97 * of work items waiting for completion 98 */ 99 struct list_head order_list; 100 struct list_head prio_order_list; 101 102 /* lock for finding the next worker thread to queue on */ 103 spinlock_t lock; 104 105 /* lock for the ordered lists */ 106 spinlock_t order_lock; 107 108 /* extra name for this worker, used for current->name */ 109 char *name; 110 }; 111 112 void btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work); 113 int btrfs_start_workers(struct btrfs_workers *workers); 114 int btrfs_stop_workers(struct btrfs_workers *workers); 115 void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max, 116 struct btrfs_workers *async_starter); 117 int btrfs_requeue_work(struct btrfs_work *work); 118 void btrfs_set_work_high_prio(struct btrfs_work *work); 119 #endif 120