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22a9d645 AV |
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 | ||
16 | Goals and Theory of Operation | |
17 | ||
18 | The primary goal of this feature is to reduce the kernel boot time, | |
19 | by doing various independent hardware delays and discovery operations | |
20 | decoupled and not strictly serialized. | |
21 | ||
22 | More specifically, the asynchronous function call concept allows | |
23 | certain operations (primarily during system boot) to happen | |
24 | asynchronously, out of order, while these operations still | |
25 | have their externally visible parts happen sequentially and in-order. | |
26 | (not unlike how out-of-order CPUs retire their instructions in order) | |
27 | ||
28 | Key to the asynchronous function call implementation is the concept of | |
29 | a "sequence cookie" (which, although it has an abstracted type, can be | |
30 | thought of as a monotonically incrementing number). | |
31 | ||
32 | The async core will assign each scheduled event such a sequence cookie and | |
33 | pass this to the called functions. | |
34 | ||
35 | The asynchronously called function should before doing a globally visible | |
36 | operation, such as registering device numbers, call the | |
37 | async_synchronize_cookie() function and pass in its own cookie. The | |
38 | async_synchronize_cookie() function will make sure that all asynchronous | |
39 | operations that were scheduled prior to the operation corresponding with the | |
40 | cookie have completed. | |
41 | ||
42 | Subsystem/driver initialization code that scheduled asynchronous probe | |
43 | functions, but which shares global resources with other drivers/subsystems | |
44 | that do not use the asynchronous call feature, need to do a full | |
45 | synchronization with the async_synchronize_full() function, before returning | |
46 | from their init function. This is to maintain strict ordering between the | |
47 | asynchronous and synchronous parts of the kernel. | |
48 | ||
49 | */ | |
50 | ||
51 | #include <linux/async.h> | |
84c15027 PM |
52 | #include <linux/atomic.h> |
53 | #include <linux/ktime.h> | |
9984de1a | 54 | #include <linux/export.h> |
22a9d645 AV |
55 | #include <linux/wait.h> |
56 | #include <linux/sched.h> | |
5a0e3ad6 | 57 | #include <linux/slab.h> |
083b804c | 58 | #include <linux/workqueue.h> |
22a9d645 | 59 | |
84b233ad TH |
60 | #include "workqueue_internal.h" |
61 | ||
22a9d645 AV |
62 | static async_cookie_t next_cookie = 1; |
63 | ||
c68eee14 TH |
64 | #define MAX_WORK 32768 |
65 | #define ASYNC_COOKIE_MAX ULLONG_MAX /* infinity cookie */ | |
22a9d645 AV |
66 | |
67 | static LIST_HEAD(async_pending); | |
8723d503 | 68 | static ASYNC_DOMAIN(async_dfl_domain); |
a4683487 | 69 | static LIST_HEAD(async_domains); |
22a9d645 | 70 | static DEFINE_SPINLOCK(async_lock); |
a4683487 | 71 | static DEFINE_MUTEX(async_register_mutex); |
22a9d645 AV |
72 | |
73 | struct async_entry { | |
083b804c TH |
74 | struct list_head list; |
75 | struct work_struct work; | |
76 | async_cookie_t cookie; | |
77 | async_func_ptr *func; | |
78 | void *data; | |
8723d503 | 79 | struct async_domain *domain; |
22a9d645 AV |
80 | }; |
81 | ||
82 | static DECLARE_WAIT_QUEUE_HEAD(async_done); | |
22a9d645 AV |
83 | |
84 | static atomic_t entry_count; | |
22a9d645 | 85 | |
22a9d645 AV |
86 | |
87 | /* | |
88 | * MUST be called with the lock held! | |
89 | */ | |
8723d503 | 90 | static async_cookie_t __lowest_in_progress(struct async_domain *domain) |
22a9d645 | 91 | { |
c68eee14 TH |
92 | async_cookie_t first_running = ASYNC_COOKIE_MAX; |
93 | async_cookie_t first_pending = ASYNC_COOKIE_MAX; | |
22a9d645 | 94 | struct async_entry *entry; |
d5a877e8 | 95 | |
f56c3196 TH |
96 | /* |
97 | * Both running and pending lists are sorted but not disjoint. | |
98 | * Take the first cookies from both and return the min. | |
99 | */ | |
8723d503 TH |
100 | if (!list_empty(&domain->running)) { |
101 | entry = list_first_entry(&domain->running, typeof(*entry), list); | |
f56c3196 | 102 | first_running = entry->cookie; |
22a9d645 AV |
103 | } |
104 | ||
f56c3196 | 105 | list_for_each_entry(entry, &async_pending, list) { |
8723d503 | 106 | if (entry->domain == domain) { |
f56c3196 TH |
107 | first_pending = entry->cookie; |
108 | break; | |
109 | } | |
110 | } | |
d5a877e8 | 111 | |
f56c3196 | 112 | return min(first_running, first_pending); |
22a9d645 | 113 | } |
37a76bd4 | 114 | |
8723d503 | 115 | static async_cookie_t lowest_in_progress(struct async_domain *domain) |
37a76bd4 AV |
116 | { |
117 | unsigned long flags; | |
118 | async_cookie_t ret; | |
119 | ||
120 | spin_lock_irqsave(&async_lock, flags); | |
8723d503 | 121 | ret = __lowest_in_progress(domain); |
37a76bd4 AV |
122 | spin_unlock_irqrestore(&async_lock, flags); |
123 | return ret; | |
124 | } | |
083b804c | 125 | |
22a9d645 AV |
126 | /* |
127 | * pick the first pending entry and run it | |
128 | */ | |
083b804c | 129 | static void async_run_entry_fn(struct work_struct *work) |
22a9d645 | 130 | { |
083b804c TH |
131 | struct async_entry *entry = |
132 | container_of(work, struct async_entry, work); | |
f56c3196 | 133 | struct async_entry *pos; |
22a9d645 | 134 | unsigned long flags; |
124ff4e5 | 135 | ktime_t uninitialized_var(calltime), delta, rettime; |
8723d503 | 136 | struct async_domain *domain = entry->domain; |
22a9d645 | 137 | |
f56c3196 | 138 | /* 1) move self to the running queue, make sure it stays sorted */ |
22a9d645 | 139 | spin_lock_irqsave(&async_lock, flags); |
8723d503 | 140 | list_for_each_entry_reverse(pos, &domain->running, list) |
f56c3196 TH |
141 | if (entry->cookie < pos->cookie) |
142 | break; | |
143 | list_move_tail(&entry->list, &pos->list); | |
22a9d645 AV |
144 | spin_unlock_irqrestore(&async_lock, flags); |
145 | ||
083b804c | 146 | /* 2) run (and print duration) */ |
ad160d23 | 147 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
84c15027 PM |
148 | printk(KERN_DEBUG "calling %lli_%pF @ %i\n", |
149 | (long long)entry->cookie, | |
58763a29 | 150 | entry->func, task_pid_nr(current)); |
22a9d645 AV |
151 | calltime = ktime_get(); |
152 | } | |
153 | entry->func(entry->data, entry->cookie); | |
ad160d23 | 154 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
22a9d645 AV |
155 | rettime = ktime_get(); |
156 | delta = ktime_sub(rettime, calltime); | |
84c15027 | 157 | printk(KERN_DEBUG "initcall %lli_%pF returned 0 after %lld usecs\n", |
58763a29 AM |
158 | (long long)entry->cookie, |
159 | entry->func, | |
160 | (long long)ktime_to_ns(delta) >> 10); | |
22a9d645 AV |
161 | } |
162 | ||
083b804c | 163 | /* 3) remove self from the running queue */ |
22a9d645 AV |
164 | spin_lock_irqsave(&async_lock, flags); |
165 | list_del(&entry->list); | |
8723d503 TH |
166 | if (domain->registered && --domain->count == 0) |
167 | list_del_init(&domain->node); | |
22a9d645 | 168 | |
083b804c | 169 | /* 4) free the entry */ |
22a9d645 AV |
170 | kfree(entry); |
171 | atomic_dec(&entry_count); | |
172 | ||
173 | spin_unlock_irqrestore(&async_lock, flags); | |
174 | ||
083b804c | 175 | /* 5) wake up any waiters */ |
22a9d645 | 176 | wake_up(&async_done); |
22a9d645 AV |
177 | } |
178 | ||
8723d503 | 179 | static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct async_domain *domain) |
22a9d645 AV |
180 | { |
181 | struct async_entry *entry; | |
182 | unsigned long flags; | |
183 | async_cookie_t newcookie; | |
22a9d645 AV |
184 | |
185 | /* allow irq-off callers */ | |
186 | entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC); | |
187 | ||
188 | /* | |
189 | * If we're out of memory or if there's too much work | |
190 | * pending already, we execute synchronously. | |
191 | */ | |
083b804c | 192 | if (!entry || atomic_read(&entry_count) > MAX_WORK) { |
22a9d645 AV |
193 | kfree(entry); |
194 | spin_lock_irqsave(&async_lock, flags); | |
195 | newcookie = next_cookie++; | |
196 | spin_unlock_irqrestore(&async_lock, flags); | |
197 | ||
198 | /* low on memory.. run synchronously */ | |
199 | ptr(data, newcookie); | |
200 | return newcookie; | |
201 | } | |
083b804c | 202 | INIT_WORK(&entry->work, async_run_entry_fn); |
22a9d645 AV |
203 | entry->func = ptr; |
204 | entry->data = data; | |
8723d503 | 205 | entry->domain = domain; |
22a9d645 AV |
206 | |
207 | spin_lock_irqsave(&async_lock, flags); | |
208 | newcookie = entry->cookie = next_cookie++; | |
209 | list_add_tail(&entry->list, &async_pending); | |
8723d503 TH |
210 | if (domain->registered && domain->count++ == 0) |
211 | list_add_tail(&domain->node, &async_domains); | |
22a9d645 AV |
212 | atomic_inc(&entry_count); |
213 | spin_unlock_irqrestore(&async_lock, flags); | |
083b804c | 214 | |
774a1221 TH |
215 | /* mark that this task has queued an async job, used by module init */ |
216 | current->flags |= PF_USED_ASYNC; | |
217 | ||
083b804c TH |
218 | /* schedule for execution */ |
219 | queue_work(system_unbound_wq, &entry->work); | |
220 | ||
22a9d645 AV |
221 | return newcookie; |
222 | } | |
223 | ||
f30d5b30 CH |
224 | /** |
225 | * async_schedule - schedule a function for asynchronous execution | |
226 | * @ptr: function to execute asynchronously | |
227 | * @data: data pointer to pass to the function | |
228 | * | |
229 | * Returns an async_cookie_t that may be used for checkpointing later. | |
230 | * Note: This function may be called from atomic or non-atomic contexts. | |
231 | */ | |
22a9d645 AV |
232 | async_cookie_t async_schedule(async_func_ptr *ptr, void *data) |
233 | { | |
8723d503 | 234 | return __async_schedule(ptr, data, &async_dfl_domain); |
22a9d645 AV |
235 | } |
236 | EXPORT_SYMBOL_GPL(async_schedule); | |
237 | ||
f30d5b30 | 238 | /** |
766ccb9e | 239 | * async_schedule_domain - schedule a function for asynchronous execution within a certain domain |
f30d5b30 CH |
240 | * @ptr: function to execute asynchronously |
241 | * @data: data pointer to pass to the function | |
8723d503 | 242 | * @domain: the domain |
f30d5b30 CH |
243 | * |
244 | * Returns an async_cookie_t that may be used for checkpointing later. | |
8723d503 TH |
245 | * @domain may be used in the async_synchronize_*_domain() functions to |
246 | * wait within a certain synchronization domain rather than globally. A | |
247 | * synchronization domain is specified via @domain. Note: This function | |
248 | * may be called from atomic or non-atomic contexts. | |
f30d5b30 | 249 | */ |
766ccb9e | 250 | async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data, |
8723d503 | 251 | struct async_domain *domain) |
22a9d645 | 252 | { |
8723d503 | 253 | return __async_schedule(ptr, data, domain); |
22a9d645 | 254 | } |
766ccb9e | 255 | EXPORT_SYMBOL_GPL(async_schedule_domain); |
22a9d645 | 256 | |
f30d5b30 CH |
257 | /** |
258 | * async_synchronize_full - synchronize all asynchronous function calls | |
259 | * | |
260 | * This function waits until all asynchronous function calls have been done. | |
261 | */ | |
22a9d645 AV |
262 | void async_synchronize_full(void) |
263 | { | |
a4683487 | 264 | mutex_lock(&async_register_mutex); |
33b04b93 | 265 | do { |
a4683487 DW |
266 | struct async_domain *domain = NULL; |
267 | ||
268 | spin_lock_irq(&async_lock); | |
269 | if (!list_empty(&async_domains)) | |
270 | domain = list_first_entry(&async_domains, typeof(*domain), node); | |
271 | spin_unlock_irq(&async_lock); | |
272 | ||
c68eee14 | 273 | async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain); |
a4683487 DW |
274 | } while (!list_empty(&async_domains)); |
275 | mutex_unlock(&async_register_mutex); | |
22a9d645 AV |
276 | } |
277 | EXPORT_SYMBOL_GPL(async_synchronize_full); | |
278 | ||
a4683487 DW |
279 | /** |
280 | * async_unregister_domain - ensure no more anonymous waiters on this domain | |
281 | * @domain: idle domain to flush out of any async_synchronize_full instances | |
282 | * | |
283 | * async_synchronize_{cookie|full}_domain() are not flushed since callers | |
284 | * of these routines should know the lifetime of @domain | |
285 | * | |
286 | * Prefer ASYNC_DOMAIN_EXCLUSIVE() declarations over flushing | |
287 | */ | |
288 | void async_unregister_domain(struct async_domain *domain) | |
289 | { | |
290 | mutex_lock(&async_register_mutex); | |
291 | spin_lock_irq(&async_lock); | |
292 | WARN_ON(!domain->registered || !list_empty(&domain->node) || | |
8723d503 | 293 | !list_empty(&domain->running)); |
a4683487 DW |
294 | domain->registered = 0; |
295 | spin_unlock_irq(&async_lock); | |
296 | mutex_unlock(&async_register_mutex); | |
297 | } | |
298 | EXPORT_SYMBOL_GPL(async_unregister_domain); | |
299 | ||
f30d5b30 | 300 | /** |
766ccb9e | 301 | * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain |
8723d503 | 302 | * @domain: the domain to synchronize |
f30d5b30 | 303 | * |
766ccb9e | 304 | * This function waits until all asynchronous function calls for the |
8723d503 | 305 | * synchronization domain specified by @domain have been done. |
f30d5b30 | 306 | */ |
2955b47d | 307 | void async_synchronize_full_domain(struct async_domain *domain) |
22a9d645 | 308 | { |
c68eee14 | 309 | async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain); |
22a9d645 | 310 | } |
766ccb9e | 311 | EXPORT_SYMBOL_GPL(async_synchronize_full_domain); |
22a9d645 | 312 | |
f30d5b30 | 313 | /** |
766ccb9e | 314 | * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing |
f30d5b30 | 315 | * @cookie: async_cookie_t to use as checkpoint |
8723d503 | 316 | * @domain: the domain to synchronize |
f30d5b30 | 317 | * |
766ccb9e | 318 | * This function waits until all asynchronous function calls for the |
8723d503 TH |
319 | * synchronization domain specified by @domain submitted prior to @cookie |
320 | * have been done. | |
f30d5b30 | 321 | */ |
8723d503 | 322 | void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain) |
22a9d645 | 323 | { |
124ff4e5 | 324 | ktime_t uninitialized_var(starttime), delta, endtime; |
22a9d645 | 325 | |
8723d503 | 326 | if (!domain) |
a4683487 DW |
327 | return; |
328 | ||
ad160d23 | 329 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
84c15027 | 330 | printk(KERN_DEBUG "async_waiting @ %i\n", task_pid_nr(current)); |
22a9d645 AV |
331 | starttime = ktime_get(); |
332 | } | |
333 | ||
8723d503 | 334 | wait_event(async_done, lowest_in_progress(domain) >= cookie); |
22a9d645 | 335 | |
ad160d23 | 336 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
22a9d645 AV |
337 | endtime = ktime_get(); |
338 | delta = ktime_sub(endtime, starttime); | |
339 | ||
84c15027 | 340 | printk(KERN_DEBUG "async_continuing @ %i after %lli usec\n", |
58763a29 AM |
341 | task_pid_nr(current), |
342 | (long long)ktime_to_ns(delta) >> 10); | |
22a9d645 AV |
343 | } |
344 | } | |
766ccb9e | 345 | EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain); |
22a9d645 | 346 | |
f30d5b30 CH |
347 | /** |
348 | * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing | |
349 | * @cookie: async_cookie_t to use as checkpoint | |
350 | * | |
351 | * This function waits until all asynchronous function calls prior to @cookie | |
352 | * have been done. | |
353 | */ | |
22a9d645 AV |
354 | void async_synchronize_cookie(async_cookie_t cookie) |
355 | { | |
8723d503 | 356 | async_synchronize_cookie_domain(cookie, &async_dfl_domain); |
22a9d645 AV |
357 | } |
358 | EXPORT_SYMBOL_GPL(async_synchronize_cookie); | |
84b233ad TH |
359 | |
360 | /** | |
361 | * current_is_async - is %current an async worker task? | |
362 | * | |
363 | * Returns %true if %current is an async worker task. | |
364 | */ | |
365 | bool current_is_async(void) | |
366 | { | |
367 | struct worker *worker = current_wq_worker(); | |
368 | ||
369 | return worker && worker->current_func == async_run_entry_fn; | |
370 | } |