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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 | ||
22a9d645 AV |
64 | #define MAX_WORK 32768 |
65 | ||
66 | static LIST_HEAD(async_pending); | |
2955b47d | 67 | static ASYNC_DOMAIN(async_running); |
a4683487 | 68 | static LIST_HEAD(async_domains); |
22a9d645 | 69 | static DEFINE_SPINLOCK(async_lock); |
a4683487 | 70 | static DEFINE_MUTEX(async_register_mutex); |
22a9d645 AV |
71 | |
72 | struct async_entry { | |
083b804c TH |
73 | struct list_head list; |
74 | struct work_struct work; | |
75 | async_cookie_t cookie; | |
76 | async_func_ptr *func; | |
77 | void *data; | |
2955b47d | 78 | struct async_domain *running; |
22a9d645 AV |
79 | }; |
80 | ||
81 | static DECLARE_WAIT_QUEUE_HEAD(async_done); | |
22a9d645 AV |
82 | |
83 | static atomic_t entry_count; | |
22a9d645 | 84 | |
22a9d645 AV |
85 | |
86 | /* | |
87 | * MUST be called with the lock held! | |
88 | */ | |
2955b47d | 89 | static async_cookie_t __lowest_in_progress(struct async_domain *running) |
22a9d645 AV |
90 | { |
91 | struct async_entry *entry; | |
d5a877e8 | 92 | |
2955b47d DW |
93 | if (!list_empty(&running->domain)) { |
94 | entry = list_first_entry(&running->domain, typeof(*entry), list); | |
3af968e0 | 95 | return entry->cookie; |
22a9d645 AV |
96 | } |
97 | ||
3af968e0 LT |
98 | list_for_each_entry(entry, &async_pending, list) |
99 | if (entry->running == running) | |
100 | return entry->cookie; | |
d5a877e8 | 101 | |
3af968e0 | 102 | return next_cookie; /* "infinity" value */ |
22a9d645 | 103 | } |
37a76bd4 | 104 | |
2955b47d | 105 | static async_cookie_t lowest_in_progress(struct async_domain *running) |
37a76bd4 AV |
106 | { |
107 | unsigned long flags; | |
108 | async_cookie_t ret; | |
109 | ||
110 | spin_lock_irqsave(&async_lock, flags); | |
111 | ret = __lowest_in_progress(running); | |
112 | spin_unlock_irqrestore(&async_lock, flags); | |
113 | return ret; | |
114 | } | |
083b804c | 115 | |
22a9d645 AV |
116 | /* |
117 | * pick the first pending entry and run it | |
118 | */ | |
083b804c | 119 | static void async_run_entry_fn(struct work_struct *work) |
22a9d645 | 120 | { |
083b804c TH |
121 | struct async_entry *entry = |
122 | container_of(work, struct async_entry, work); | |
22a9d645 | 123 | unsigned long flags; |
124ff4e5 | 124 | ktime_t uninitialized_var(calltime), delta, rettime; |
2955b47d | 125 | struct async_domain *running = entry->running; |
22a9d645 | 126 | |
083b804c | 127 | /* 1) move self to the running queue */ |
22a9d645 | 128 | spin_lock_irqsave(&async_lock, flags); |
2955b47d | 129 | list_move_tail(&entry->list, &running->domain); |
22a9d645 AV |
130 | spin_unlock_irqrestore(&async_lock, flags); |
131 | ||
083b804c | 132 | /* 2) run (and print duration) */ |
ad160d23 | 133 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
84c15027 PM |
134 | printk(KERN_DEBUG "calling %lli_%pF @ %i\n", |
135 | (long long)entry->cookie, | |
58763a29 | 136 | entry->func, task_pid_nr(current)); |
22a9d645 AV |
137 | calltime = ktime_get(); |
138 | } | |
139 | entry->func(entry->data, entry->cookie); | |
ad160d23 | 140 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
22a9d645 AV |
141 | rettime = ktime_get(); |
142 | delta = ktime_sub(rettime, calltime); | |
84c15027 | 143 | printk(KERN_DEBUG "initcall %lli_%pF returned 0 after %lld usecs\n", |
58763a29 AM |
144 | (long long)entry->cookie, |
145 | entry->func, | |
146 | (long long)ktime_to_ns(delta) >> 10); | |
22a9d645 AV |
147 | } |
148 | ||
083b804c | 149 | /* 3) remove self from the running queue */ |
22a9d645 AV |
150 | spin_lock_irqsave(&async_lock, flags); |
151 | list_del(&entry->list); | |
a4683487 DW |
152 | if (running->registered && --running->count == 0) |
153 | list_del_init(&running->node); | |
22a9d645 | 154 | |
083b804c | 155 | /* 4) free the entry */ |
22a9d645 AV |
156 | kfree(entry); |
157 | atomic_dec(&entry_count); | |
158 | ||
159 | spin_unlock_irqrestore(&async_lock, flags); | |
160 | ||
083b804c | 161 | /* 5) wake up any waiters */ |
22a9d645 | 162 | wake_up(&async_done); |
22a9d645 AV |
163 | } |
164 | ||
2955b47d | 165 | static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct async_domain *running) |
22a9d645 AV |
166 | { |
167 | struct async_entry *entry; | |
168 | unsigned long flags; | |
169 | async_cookie_t newcookie; | |
22a9d645 AV |
170 | |
171 | /* allow irq-off callers */ | |
172 | entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC); | |
173 | ||
174 | /* | |
175 | * If we're out of memory or if there's too much work | |
176 | * pending already, we execute synchronously. | |
177 | */ | |
083b804c | 178 | if (!entry || atomic_read(&entry_count) > MAX_WORK) { |
22a9d645 AV |
179 | kfree(entry); |
180 | spin_lock_irqsave(&async_lock, flags); | |
181 | newcookie = next_cookie++; | |
182 | spin_unlock_irqrestore(&async_lock, flags); | |
183 | ||
184 | /* low on memory.. run synchronously */ | |
185 | ptr(data, newcookie); | |
186 | return newcookie; | |
187 | } | |
083b804c | 188 | INIT_WORK(&entry->work, async_run_entry_fn); |
22a9d645 AV |
189 | entry->func = ptr; |
190 | entry->data = data; | |
191 | entry->running = running; | |
192 | ||
193 | spin_lock_irqsave(&async_lock, flags); | |
194 | newcookie = entry->cookie = next_cookie++; | |
195 | list_add_tail(&entry->list, &async_pending); | |
a4683487 DW |
196 | if (running->registered && running->count++ == 0) |
197 | list_add_tail(&running->node, &async_domains); | |
22a9d645 AV |
198 | atomic_inc(&entry_count); |
199 | spin_unlock_irqrestore(&async_lock, flags); | |
083b804c TH |
200 | |
201 | /* schedule for execution */ | |
202 | queue_work(system_unbound_wq, &entry->work); | |
203 | ||
22a9d645 AV |
204 | return newcookie; |
205 | } | |
206 | ||
f30d5b30 CH |
207 | /** |
208 | * async_schedule - schedule a function for asynchronous execution | |
209 | * @ptr: function to execute asynchronously | |
210 | * @data: data pointer to pass to the function | |
211 | * | |
212 | * Returns an async_cookie_t that may be used for checkpointing later. | |
213 | * Note: This function may be called from atomic or non-atomic contexts. | |
214 | */ | |
22a9d645 AV |
215 | async_cookie_t async_schedule(async_func_ptr *ptr, void *data) |
216 | { | |
7a89bbc7 | 217 | return __async_schedule(ptr, data, &async_running); |
22a9d645 AV |
218 | } |
219 | EXPORT_SYMBOL_GPL(async_schedule); | |
220 | ||
f30d5b30 | 221 | /** |
766ccb9e | 222 | * async_schedule_domain - schedule a function for asynchronous execution within a certain domain |
f30d5b30 CH |
223 | * @ptr: function to execute asynchronously |
224 | * @data: data pointer to pass to the function | |
766ccb9e | 225 | * @running: running list for the domain |
f30d5b30 CH |
226 | * |
227 | * Returns an async_cookie_t that may be used for checkpointing later. | |
766ccb9e CH |
228 | * @running may be used in the async_synchronize_*_domain() functions |
229 | * to wait within a certain synchronization domain rather than globally. | |
230 | * A synchronization domain is specified via the running queue @running to use. | |
f30d5b30 CH |
231 | * Note: This function may be called from atomic or non-atomic contexts. |
232 | */ | |
766ccb9e | 233 | async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data, |
2955b47d | 234 | struct async_domain *running) |
22a9d645 AV |
235 | { |
236 | return __async_schedule(ptr, data, running); | |
237 | } | |
766ccb9e | 238 | EXPORT_SYMBOL_GPL(async_schedule_domain); |
22a9d645 | 239 | |
f30d5b30 CH |
240 | /** |
241 | * async_synchronize_full - synchronize all asynchronous function calls | |
242 | * | |
243 | * This function waits until all asynchronous function calls have been done. | |
244 | */ | |
22a9d645 AV |
245 | void async_synchronize_full(void) |
246 | { | |
a4683487 | 247 | mutex_lock(&async_register_mutex); |
33b04b93 | 248 | do { |
a4683487 DW |
249 | struct async_domain *domain = NULL; |
250 | ||
251 | spin_lock_irq(&async_lock); | |
252 | if (!list_empty(&async_domains)) | |
253 | domain = list_first_entry(&async_domains, typeof(*domain), node); | |
254 | spin_unlock_irq(&async_lock); | |
255 | ||
256 | async_synchronize_cookie_domain(next_cookie, domain); | |
257 | } while (!list_empty(&async_domains)); | |
258 | mutex_unlock(&async_register_mutex); | |
22a9d645 AV |
259 | } |
260 | EXPORT_SYMBOL_GPL(async_synchronize_full); | |
261 | ||
a4683487 DW |
262 | /** |
263 | * async_unregister_domain - ensure no more anonymous waiters on this domain | |
264 | * @domain: idle domain to flush out of any async_synchronize_full instances | |
265 | * | |
266 | * async_synchronize_{cookie|full}_domain() are not flushed since callers | |
267 | * of these routines should know the lifetime of @domain | |
268 | * | |
269 | * Prefer ASYNC_DOMAIN_EXCLUSIVE() declarations over flushing | |
270 | */ | |
271 | void async_unregister_domain(struct async_domain *domain) | |
272 | { | |
273 | mutex_lock(&async_register_mutex); | |
274 | spin_lock_irq(&async_lock); | |
275 | WARN_ON(!domain->registered || !list_empty(&domain->node) || | |
276 | !list_empty(&domain->domain)); | |
277 | domain->registered = 0; | |
278 | spin_unlock_irq(&async_lock); | |
279 | mutex_unlock(&async_register_mutex); | |
280 | } | |
281 | EXPORT_SYMBOL_GPL(async_unregister_domain); | |
282 | ||
f30d5b30 | 283 | /** |
766ccb9e | 284 | * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain |
2955b47d | 285 | * @domain: running list to synchronize on |
f30d5b30 | 286 | * |
766ccb9e | 287 | * This function waits until all asynchronous function calls for the |
2955b47d | 288 | * synchronization domain specified by the running list @domain have been done. |
f30d5b30 | 289 | */ |
2955b47d | 290 | void async_synchronize_full_domain(struct async_domain *domain) |
22a9d645 | 291 | { |
2955b47d | 292 | async_synchronize_cookie_domain(next_cookie, domain); |
22a9d645 | 293 | } |
766ccb9e | 294 | EXPORT_SYMBOL_GPL(async_synchronize_full_domain); |
22a9d645 | 295 | |
f30d5b30 | 296 | /** |
766ccb9e | 297 | * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing |
f30d5b30 CH |
298 | * @cookie: async_cookie_t to use as checkpoint |
299 | * @running: running list to synchronize on | |
300 | * | |
766ccb9e | 301 | * This function waits until all asynchronous function calls for the |
2955b47d | 302 | * synchronization domain specified by running list @running submitted |
766ccb9e | 303 | * prior to @cookie have been done. |
f30d5b30 | 304 | */ |
2955b47d | 305 | void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *running) |
22a9d645 | 306 | { |
124ff4e5 | 307 | ktime_t uninitialized_var(starttime), delta, endtime; |
22a9d645 | 308 | |
a4683487 DW |
309 | if (!running) |
310 | return; | |
311 | ||
ad160d23 | 312 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
84c15027 | 313 | printk(KERN_DEBUG "async_waiting @ %i\n", task_pid_nr(current)); |
22a9d645 AV |
314 | starttime = ktime_get(); |
315 | } | |
316 | ||
37a76bd4 | 317 | wait_event(async_done, lowest_in_progress(running) >= cookie); |
22a9d645 | 318 | |
ad160d23 | 319 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
22a9d645 AV |
320 | endtime = ktime_get(); |
321 | delta = ktime_sub(endtime, starttime); | |
322 | ||
84c15027 | 323 | printk(KERN_DEBUG "async_continuing @ %i after %lli usec\n", |
58763a29 AM |
324 | task_pid_nr(current), |
325 | (long long)ktime_to_ns(delta) >> 10); | |
22a9d645 AV |
326 | } |
327 | } | |
766ccb9e | 328 | EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain); |
22a9d645 | 329 | |
f30d5b30 CH |
330 | /** |
331 | * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing | |
332 | * @cookie: async_cookie_t to use as checkpoint | |
333 | * | |
334 | * This function waits until all asynchronous function calls prior to @cookie | |
335 | * have been done. | |
336 | */ | |
22a9d645 AV |
337 | void async_synchronize_cookie(async_cookie_t cookie) |
338 | { | |
766ccb9e | 339 | async_synchronize_cookie_domain(cookie, &async_running); |
22a9d645 AV |
340 | } |
341 | EXPORT_SYMBOL_GPL(async_synchronize_cookie); | |
84b233ad TH |
342 | |
343 | /** | |
344 | * current_is_async - is %current an async worker task? | |
345 | * | |
346 | * Returns %true if %current is an async worker task. | |
347 | */ | |
348 | bool current_is_async(void) | |
349 | { | |
350 | struct worker *worker = current_wq_worker(); | |
351 | ||
352 | return worker && worker->current_func == async_run_entry_fn; | |
353 | } |