Loading...
1/*
2 * async.c: Asynchronous function calls for boot performance
3 *
4 * (C) Copyright 2009 Intel Corporation
5 * Author: Arjan van de Ven <arjan@linux.intel.com>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; version 2
10 * of the License.
11 */
12
13
14/*
15
16Goals and Theory of Operation
17
18The primary goal of this feature is to reduce the kernel boot time,
19by doing various independent hardware delays and discovery operations
20decoupled and not strictly serialized.
21
22More specifically, the asynchronous function call concept allows
23certain operations (primarily during system boot) to happen
24asynchronously, out of order, while these operations still
25have their externally visible parts happen sequentially and in-order.
26(not unlike how out-of-order CPUs retire their instructions in order)
27
28Key to the asynchronous function call implementation is the concept of
29a "sequence cookie" (which, although it has an abstracted type, can be
30thought of as a monotonically incrementing number).
31
32The async core will assign each scheduled event such a sequence cookie and
33pass this to the called functions.
34
35The asynchronously called function should before doing a globally visible
36operation, such as registering device numbers, call the
37async_synchronize_cookie() function and pass in its own cookie. The
38async_synchronize_cookie() function will make sure that all asynchronous
39operations that were scheduled prior to the operation corresponding with the
40cookie have completed.
41
42Subsystem/driver initialization code that scheduled asynchronous probe
43functions, but which shares global resources with other drivers/subsystems
44that do not use the asynchronous call feature, need to do a full
45synchronization with the async_synchronize_full() function, before returning
46from their init function. This is to maintain strict ordering between the
47asynchronous and synchronous parts of the kernel.
48
49*/
50
51#include <linux/async.h>
52#include <linux/atomic.h>
53#include <linux/ktime.h>
54#include <linux/export.h>
55#include <linux/wait.h>
56#include <linux/sched.h>
57#include <linux/slab.h>
58#include <linux/workqueue.h>
59
60#include "workqueue_internal.h"
61
62static async_cookie_t next_cookie = 1;
63
64#define MAX_WORK 32768
65#define ASYNC_COOKIE_MAX ULLONG_MAX /* infinity cookie */
66
67static LIST_HEAD(async_global_pending); /* pending from all registered doms */
68static ASYNC_DOMAIN(async_dfl_domain);
69static DEFINE_SPINLOCK(async_lock);
70
71struct async_entry {
72 struct list_head domain_list;
73 struct list_head global_list;
74 struct work_struct work;
75 async_cookie_t cookie;
76 async_func_t func;
77 void *data;
78 struct async_domain *domain;
79};
80
81static DECLARE_WAIT_QUEUE_HEAD(async_done);
82
83static atomic_t entry_count;
84
85static async_cookie_t lowest_in_progress(struct async_domain *domain)
86{
87 struct async_entry *first = NULL;
88 async_cookie_t ret = ASYNC_COOKIE_MAX;
89 unsigned long flags;
90
91 spin_lock_irqsave(&async_lock, flags);
92
93 if (domain) {
94 if (!list_empty(&domain->pending))
95 first = list_first_entry(&domain->pending,
96 struct async_entry, domain_list);
97 } else {
98 if (!list_empty(&async_global_pending))
99 first = list_first_entry(&async_global_pending,
100 struct async_entry, global_list);
101 }
102
103 if (first)
104 ret = first->cookie;
105
106 spin_unlock_irqrestore(&async_lock, flags);
107 return ret;
108}
109
110/*
111 * pick the first pending entry and run it
112 */
113static void async_run_entry_fn(struct work_struct *work)
114{
115 struct async_entry *entry =
116 container_of(work, struct async_entry, work);
117 unsigned long flags;
118 ktime_t uninitialized_var(calltime), delta, rettime;
119
120 /* 1) run (and print duration) */
121 if (initcall_debug && system_state < SYSTEM_RUNNING) {
122 pr_debug("calling %lli_%pF @ %i\n",
123 (long long)entry->cookie,
124 entry->func, task_pid_nr(current));
125 calltime = ktime_get();
126 }
127 entry->func(entry->data, entry->cookie);
128 if (initcall_debug && system_state < SYSTEM_RUNNING) {
129 rettime = ktime_get();
130 delta = ktime_sub(rettime, calltime);
131 pr_debug("initcall %lli_%pF returned 0 after %lld usecs\n",
132 (long long)entry->cookie,
133 entry->func,
134 (long long)ktime_to_ns(delta) >> 10);
135 }
136
137 /* 2) remove self from the pending queues */
138 spin_lock_irqsave(&async_lock, flags);
139 list_del_init(&entry->domain_list);
140 list_del_init(&entry->global_list);
141
142 /* 3) free the entry */
143 kfree(entry);
144 atomic_dec(&entry_count);
145
146 spin_unlock_irqrestore(&async_lock, flags);
147
148 /* 4) wake up any waiters */
149 wake_up(&async_done);
150}
151
152static async_cookie_t __async_schedule(async_func_t func, void *data, struct async_domain *domain)
153{
154 struct async_entry *entry;
155 unsigned long flags;
156 async_cookie_t newcookie;
157
158 /* allow irq-off callers */
159 entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
160
161 /*
162 * If we're out of memory or if there's too much work
163 * pending already, we execute synchronously.
164 */
165 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
166 kfree(entry);
167 spin_lock_irqsave(&async_lock, flags);
168 newcookie = next_cookie++;
169 spin_unlock_irqrestore(&async_lock, flags);
170
171 /* low on memory.. run synchronously */
172 func(data, newcookie);
173 return newcookie;
174 }
175 INIT_LIST_HEAD(&entry->domain_list);
176 INIT_LIST_HEAD(&entry->global_list);
177 INIT_WORK(&entry->work, async_run_entry_fn);
178 entry->func = func;
179 entry->data = data;
180 entry->domain = domain;
181
182 spin_lock_irqsave(&async_lock, flags);
183
184 /* allocate cookie and queue */
185 newcookie = entry->cookie = next_cookie++;
186
187 list_add_tail(&entry->domain_list, &domain->pending);
188 if (domain->registered)
189 list_add_tail(&entry->global_list, &async_global_pending);
190
191 atomic_inc(&entry_count);
192 spin_unlock_irqrestore(&async_lock, flags);
193
194 /* mark that this task has queued an async job, used by module init */
195 current->flags |= PF_USED_ASYNC;
196
197 /* schedule for execution */
198 queue_work(system_unbound_wq, &entry->work);
199
200 return newcookie;
201}
202
203/**
204 * async_schedule - schedule a function for asynchronous execution
205 * @func: function to execute asynchronously
206 * @data: data pointer to pass to the function
207 *
208 * Returns an async_cookie_t that may be used for checkpointing later.
209 * Note: This function may be called from atomic or non-atomic contexts.
210 */
211async_cookie_t async_schedule(async_func_t func, void *data)
212{
213 return __async_schedule(func, data, &async_dfl_domain);
214}
215EXPORT_SYMBOL_GPL(async_schedule);
216
217/**
218 * async_schedule_domain - schedule a function for asynchronous execution within a certain domain
219 * @func: function to execute asynchronously
220 * @data: data pointer to pass to the function
221 * @domain: the domain
222 *
223 * Returns an async_cookie_t that may be used for checkpointing later.
224 * @domain may be used in the async_synchronize_*_domain() functions to
225 * wait within a certain synchronization domain rather than globally. A
226 * synchronization domain is specified via @domain. Note: This function
227 * may be called from atomic or non-atomic contexts.
228 */
229async_cookie_t async_schedule_domain(async_func_t func, void *data,
230 struct async_domain *domain)
231{
232 return __async_schedule(func, data, domain);
233}
234EXPORT_SYMBOL_GPL(async_schedule_domain);
235
236/**
237 * async_synchronize_full - synchronize all asynchronous function calls
238 *
239 * This function waits until all asynchronous function calls have been done.
240 */
241void async_synchronize_full(void)
242{
243 async_synchronize_full_domain(NULL);
244}
245EXPORT_SYMBOL_GPL(async_synchronize_full);
246
247/**
248 * async_unregister_domain - ensure no more anonymous waiters on this domain
249 * @domain: idle domain to flush out of any async_synchronize_full instances
250 *
251 * async_synchronize_{cookie|full}_domain() are not flushed since callers
252 * of these routines should know the lifetime of @domain
253 *
254 * Prefer ASYNC_DOMAIN_EXCLUSIVE() declarations over flushing
255 */
256void async_unregister_domain(struct async_domain *domain)
257{
258 spin_lock_irq(&async_lock);
259 WARN_ON(!domain->registered || !list_empty(&domain->pending));
260 domain->registered = 0;
261 spin_unlock_irq(&async_lock);
262}
263EXPORT_SYMBOL_GPL(async_unregister_domain);
264
265/**
266 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
267 * @domain: the domain to synchronize
268 *
269 * This function waits until all asynchronous function calls for the
270 * synchronization domain specified by @domain have been done.
271 */
272void async_synchronize_full_domain(struct async_domain *domain)
273{
274 async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain);
275}
276EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
277
278/**
279 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
280 * @cookie: async_cookie_t to use as checkpoint
281 * @domain: the domain to synchronize (%NULL for all registered domains)
282 *
283 * This function waits until all asynchronous function calls for the
284 * synchronization domain specified by @domain submitted prior to @cookie
285 * have been done.
286 */
287void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain)
288{
289 ktime_t uninitialized_var(starttime), delta, endtime;
290
291 if (initcall_debug && system_state < SYSTEM_RUNNING) {
292 pr_debug("async_waiting @ %i\n", task_pid_nr(current));
293 starttime = ktime_get();
294 }
295
296 wait_event(async_done, lowest_in_progress(domain) >= cookie);
297
298 if (initcall_debug && system_state < SYSTEM_RUNNING) {
299 endtime = ktime_get();
300 delta = ktime_sub(endtime, starttime);
301
302 pr_debug("async_continuing @ %i after %lli usec\n",
303 task_pid_nr(current),
304 (long long)ktime_to_ns(delta) >> 10);
305 }
306}
307EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
308
309/**
310 * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing
311 * @cookie: async_cookie_t to use as checkpoint
312 *
313 * This function waits until all asynchronous function calls prior to @cookie
314 * have been done.
315 */
316void async_synchronize_cookie(async_cookie_t cookie)
317{
318 async_synchronize_cookie_domain(cookie, &async_dfl_domain);
319}
320EXPORT_SYMBOL_GPL(async_synchronize_cookie);
321
322/**
323 * current_is_async - is %current an async worker task?
324 *
325 * Returns %true if %current is an async worker task.
326 */
327bool current_is_async(void)
328{
329 struct worker *worker = current_wq_worker();
330
331 return worker && worker->current_func == async_run_entry_fn;
332}
333EXPORT_SYMBOL_GPL(current_is_async);
1/*
2 * async.c: Asynchronous function calls for boot performance
3 *
4 * (C) Copyright 2009 Intel Corporation
5 * Author: Arjan van de Ven <arjan@linux.intel.com>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; version 2
10 * of the License.
11 */
12
13
14/*
15
16Goals and Theory of Operation
17
18The primary goal of this feature is to reduce the kernel boot time,
19by doing various independent hardware delays and discovery operations
20decoupled and not strictly serialized.
21
22More specifically, the asynchronous function call concept allows
23certain operations (primarily during system boot) to happen
24asynchronously, out of order, while these operations still
25have their externally visible parts happen sequentially and in-order.
26(not unlike how out-of-order CPUs retire their instructions in order)
27
28Key to the asynchronous function call implementation is the concept of
29a "sequence cookie" (which, although it has an abstracted type, can be
30thought of as a monotonically incrementing number).
31
32The async core will assign each scheduled event such a sequence cookie and
33pass this to the called functions.
34
35The asynchronously called function should before doing a globally visible
36operation, such as registering device numbers, call the
37async_synchronize_cookie() function and pass in its own cookie. The
38async_synchronize_cookie() function will make sure that all asynchronous
39operations that were scheduled prior to the operation corresponding with the
40cookie have completed.
41
42Subsystem/driver initialization code that scheduled asynchronous probe
43functions, but which shares global resources with other drivers/subsystems
44that do not use the asynchronous call feature, need to do a full
45synchronization with the async_synchronize_full() function, before returning
46from their init function. This is to maintain strict ordering between the
47asynchronous and synchronous parts of the kernel.
48
49*/
50
51#include <linux/async.h>
52#include <linux/atomic.h>
53#include <linux/ktime.h>
54#include <linux/module.h>
55#include <linux/wait.h>
56#include <linux/sched.h>
57#include <linux/slab.h>
58#include <linux/workqueue.h>
59
60static async_cookie_t next_cookie = 1;
61
62#define MAX_WORK 32768
63
64static LIST_HEAD(async_pending);
65static LIST_HEAD(async_running);
66static DEFINE_SPINLOCK(async_lock);
67
68struct async_entry {
69 struct list_head list;
70 struct work_struct work;
71 async_cookie_t cookie;
72 async_func_ptr *func;
73 void *data;
74 struct list_head *running;
75};
76
77static DECLARE_WAIT_QUEUE_HEAD(async_done);
78
79static atomic_t entry_count;
80
81extern int initcall_debug;
82
83
84/*
85 * MUST be called with the lock held!
86 */
87static async_cookie_t __lowest_in_progress(struct list_head *running)
88{
89 struct async_entry *entry;
90
91 if (!list_empty(running)) {
92 entry = list_first_entry(running,
93 struct async_entry, list);
94 return entry->cookie;
95 }
96
97 list_for_each_entry(entry, &async_pending, list)
98 if (entry->running == running)
99 return entry->cookie;
100
101 return next_cookie; /* "infinity" value */
102}
103
104static async_cookie_t lowest_in_progress(struct list_head *running)
105{
106 unsigned long flags;
107 async_cookie_t ret;
108
109 spin_lock_irqsave(&async_lock, flags);
110 ret = __lowest_in_progress(running);
111 spin_unlock_irqrestore(&async_lock, flags);
112 return ret;
113}
114
115/*
116 * pick the first pending entry and run it
117 */
118static void async_run_entry_fn(struct work_struct *work)
119{
120 struct async_entry *entry =
121 container_of(work, struct async_entry, work);
122 unsigned long flags;
123 ktime_t calltime, delta, rettime;
124
125 /* 1) move self to the running queue */
126 spin_lock_irqsave(&async_lock, flags);
127 list_move_tail(&entry->list, entry->running);
128 spin_unlock_irqrestore(&async_lock, flags);
129
130 /* 2) run (and print duration) */
131 if (initcall_debug && system_state == SYSTEM_BOOTING) {
132 printk(KERN_DEBUG "calling %lli_%pF @ %i\n",
133 (long long)entry->cookie,
134 entry->func, task_pid_nr(current));
135 calltime = ktime_get();
136 }
137 entry->func(entry->data, entry->cookie);
138 if (initcall_debug && system_state == SYSTEM_BOOTING) {
139 rettime = ktime_get();
140 delta = ktime_sub(rettime, calltime);
141 printk(KERN_DEBUG "initcall %lli_%pF returned 0 after %lld usecs\n",
142 (long long)entry->cookie,
143 entry->func,
144 (long long)ktime_to_ns(delta) >> 10);
145 }
146
147 /* 3) remove self from the running queue */
148 spin_lock_irqsave(&async_lock, flags);
149 list_del(&entry->list);
150
151 /* 4) free the entry */
152 kfree(entry);
153 atomic_dec(&entry_count);
154
155 spin_unlock_irqrestore(&async_lock, flags);
156
157 /* 5) wake up any waiters */
158 wake_up(&async_done);
159}
160
161static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct list_head *running)
162{
163 struct async_entry *entry;
164 unsigned long flags;
165 async_cookie_t newcookie;
166
167 /* allow irq-off callers */
168 entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
169
170 /*
171 * If we're out of memory or if there's too much work
172 * pending already, we execute synchronously.
173 */
174 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
175 kfree(entry);
176 spin_lock_irqsave(&async_lock, flags);
177 newcookie = next_cookie++;
178 spin_unlock_irqrestore(&async_lock, flags);
179
180 /* low on memory.. run synchronously */
181 ptr(data, newcookie);
182 return newcookie;
183 }
184 INIT_WORK(&entry->work, async_run_entry_fn);
185 entry->func = ptr;
186 entry->data = data;
187 entry->running = running;
188
189 spin_lock_irqsave(&async_lock, flags);
190 newcookie = entry->cookie = next_cookie++;
191 list_add_tail(&entry->list, &async_pending);
192 atomic_inc(&entry_count);
193 spin_unlock_irqrestore(&async_lock, flags);
194
195 /* schedule for execution */
196 queue_work(system_unbound_wq, &entry->work);
197
198 return newcookie;
199}
200
201/**
202 * async_schedule - schedule a function for asynchronous execution
203 * @ptr: function to execute asynchronously
204 * @data: data pointer to pass to the function
205 *
206 * Returns an async_cookie_t that may be used for checkpointing later.
207 * Note: This function may be called from atomic or non-atomic contexts.
208 */
209async_cookie_t async_schedule(async_func_ptr *ptr, void *data)
210{
211 return __async_schedule(ptr, data, &async_running);
212}
213EXPORT_SYMBOL_GPL(async_schedule);
214
215/**
216 * async_schedule_domain - schedule a function for asynchronous execution within a certain domain
217 * @ptr: function to execute asynchronously
218 * @data: data pointer to pass to the function
219 * @running: running list for the domain
220 *
221 * Returns an async_cookie_t that may be used for checkpointing later.
222 * @running may be used in the async_synchronize_*_domain() functions
223 * to wait within a certain synchronization domain rather than globally.
224 * A synchronization domain is specified via the running queue @running to use.
225 * Note: This function may be called from atomic or non-atomic contexts.
226 */
227async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data,
228 struct list_head *running)
229{
230 return __async_schedule(ptr, data, running);
231}
232EXPORT_SYMBOL_GPL(async_schedule_domain);
233
234/**
235 * async_synchronize_full - synchronize all asynchronous function calls
236 *
237 * This function waits until all asynchronous function calls have been done.
238 */
239void async_synchronize_full(void)
240{
241 do {
242 async_synchronize_cookie(next_cookie);
243 } while (!list_empty(&async_running) || !list_empty(&async_pending));
244}
245EXPORT_SYMBOL_GPL(async_synchronize_full);
246
247/**
248 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
249 * @list: running list to synchronize on
250 *
251 * This function waits until all asynchronous function calls for the
252 * synchronization domain specified by the running list @list have been done.
253 */
254void async_synchronize_full_domain(struct list_head *list)
255{
256 async_synchronize_cookie_domain(next_cookie, list);
257}
258EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
259
260/**
261 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
262 * @cookie: async_cookie_t to use as checkpoint
263 * @running: running list to synchronize on
264 *
265 * This function waits until all asynchronous function calls for the
266 * synchronization domain specified by the running list @list submitted
267 * prior to @cookie have been done.
268 */
269void async_synchronize_cookie_domain(async_cookie_t cookie,
270 struct list_head *running)
271{
272 ktime_t starttime, delta, endtime;
273
274 if (initcall_debug && system_state == SYSTEM_BOOTING) {
275 printk(KERN_DEBUG "async_waiting @ %i\n", task_pid_nr(current));
276 starttime = ktime_get();
277 }
278
279 wait_event(async_done, lowest_in_progress(running) >= cookie);
280
281 if (initcall_debug && system_state == SYSTEM_BOOTING) {
282 endtime = ktime_get();
283 delta = ktime_sub(endtime, starttime);
284
285 printk(KERN_DEBUG "async_continuing @ %i after %lli usec\n",
286 task_pid_nr(current),
287 (long long)ktime_to_ns(delta) >> 10);
288 }
289}
290EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
291
292/**
293 * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing
294 * @cookie: async_cookie_t to use as checkpoint
295 *
296 * This function waits until all asynchronous function calls prior to @cookie
297 * have been done.
298 */
299void async_synchronize_cookie(async_cookie_t cookie)
300{
301 async_synchronize_cookie_domain(cookie, &async_running);
302}
303EXPORT_SYMBOL_GPL(async_synchronize_cookie);