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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 AV |
59 | |
60 | static async_cookie_t next_cookie = 1; | |
61 | ||
22a9d645 AV |
62 | #define MAX_WORK 32768 |
63 | ||
64 | static LIST_HEAD(async_pending); | |
2955b47d | 65 | static ASYNC_DOMAIN(async_running); |
a4683487 | 66 | static LIST_HEAD(async_domains); |
22a9d645 | 67 | static DEFINE_SPINLOCK(async_lock); |
a4683487 | 68 | static DEFINE_MUTEX(async_register_mutex); |
22a9d645 AV |
69 | |
70 | struct async_entry { | |
083b804c TH |
71 | struct list_head list; |
72 | struct work_struct work; | |
73 | async_cookie_t cookie; | |
74 | async_func_ptr *func; | |
75 | void *data; | |
2955b47d | 76 | struct async_domain *running; |
22a9d645 AV |
77 | }; |
78 | ||
79 | static DECLARE_WAIT_QUEUE_HEAD(async_done); | |
22a9d645 AV |
80 | |
81 | static atomic_t entry_count; | |
22a9d645 | 82 | |
22a9d645 AV |
83 | |
84 | /* | |
85 | * MUST be called with the lock held! | |
86 | */ | |
2955b47d | 87 | static async_cookie_t __lowest_in_progress(struct async_domain *running) |
22a9d645 | 88 | { |
f56c3196 TH |
89 | async_cookie_t first_running = next_cookie; /* infinity value */ |
90 | async_cookie_t first_pending = next_cookie; /* ditto */ | |
22a9d645 | 91 | struct async_entry *entry; |
d5a877e8 | 92 | |
f56c3196 TH |
93 | /* |
94 | * Both running and pending lists are sorted but not disjoint. | |
95 | * Take the first cookies from both and return the min. | |
96 | */ | |
2955b47d DW |
97 | if (!list_empty(&running->domain)) { |
98 | entry = list_first_entry(&running->domain, typeof(*entry), list); | |
f56c3196 | 99 | first_running = entry->cookie; |
22a9d645 AV |
100 | } |
101 | ||
f56c3196 TH |
102 | list_for_each_entry(entry, &async_pending, list) { |
103 | if (entry->running == running) { | |
104 | first_pending = entry->cookie; | |
105 | break; | |
106 | } | |
107 | } | |
d5a877e8 | 108 | |
f56c3196 | 109 | return min(first_running, first_pending); |
22a9d645 | 110 | } |
37a76bd4 | 111 | |
2955b47d | 112 | static async_cookie_t lowest_in_progress(struct async_domain *running) |
37a76bd4 AV |
113 | { |
114 | unsigned long flags; | |
115 | async_cookie_t ret; | |
116 | ||
117 | spin_lock_irqsave(&async_lock, flags); | |
118 | ret = __lowest_in_progress(running); | |
119 | spin_unlock_irqrestore(&async_lock, flags); | |
120 | return ret; | |
121 | } | |
083b804c | 122 | |
22a9d645 AV |
123 | /* |
124 | * pick the first pending entry and run it | |
125 | */ | |
083b804c | 126 | static void async_run_entry_fn(struct work_struct *work) |
22a9d645 | 127 | { |
083b804c TH |
128 | struct async_entry *entry = |
129 | container_of(work, struct async_entry, work); | |
f56c3196 | 130 | struct async_entry *pos; |
22a9d645 | 131 | unsigned long flags; |
124ff4e5 | 132 | ktime_t uninitialized_var(calltime), delta, rettime; |
2955b47d | 133 | struct async_domain *running = entry->running; |
22a9d645 | 134 | |
f56c3196 | 135 | /* 1) move self to the running queue, make sure it stays sorted */ |
22a9d645 | 136 | spin_lock_irqsave(&async_lock, flags); |
f56c3196 TH |
137 | list_for_each_entry_reverse(pos, &running->domain, list) |
138 | if (entry->cookie < pos->cookie) | |
139 | break; | |
140 | list_move_tail(&entry->list, &pos->list); | |
22a9d645 AV |
141 | spin_unlock_irqrestore(&async_lock, flags); |
142 | ||
083b804c | 143 | /* 2) run (and print duration) */ |
ad160d23 | 144 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
84c15027 PM |
145 | printk(KERN_DEBUG "calling %lli_%pF @ %i\n", |
146 | (long long)entry->cookie, | |
58763a29 | 147 | entry->func, task_pid_nr(current)); |
22a9d645 AV |
148 | calltime = ktime_get(); |
149 | } | |
150 | entry->func(entry->data, entry->cookie); | |
ad160d23 | 151 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
22a9d645 AV |
152 | rettime = ktime_get(); |
153 | delta = ktime_sub(rettime, calltime); | |
84c15027 | 154 | printk(KERN_DEBUG "initcall %lli_%pF returned 0 after %lld usecs\n", |
58763a29 AM |
155 | (long long)entry->cookie, |
156 | entry->func, | |
157 | (long long)ktime_to_ns(delta) >> 10); | |
22a9d645 AV |
158 | } |
159 | ||
083b804c | 160 | /* 3) remove self from the running queue */ |
22a9d645 AV |
161 | spin_lock_irqsave(&async_lock, flags); |
162 | list_del(&entry->list); | |
a4683487 DW |
163 | if (running->registered && --running->count == 0) |
164 | list_del_init(&running->node); | |
22a9d645 | 165 | |
083b804c | 166 | /* 4) free the entry */ |
22a9d645 AV |
167 | kfree(entry); |
168 | atomic_dec(&entry_count); | |
169 | ||
170 | spin_unlock_irqrestore(&async_lock, flags); | |
171 | ||
083b804c | 172 | /* 5) wake up any waiters */ |
22a9d645 | 173 | wake_up(&async_done); |
22a9d645 AV |
174 | } |
175 | ||
2955b47d | 176 | static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct async_domain *running) |
22a9d645 AV |
177 | { |
178 | struct async_entry *entry; | |
179 | unsigned long flags; | |
180 | async_cookie_t newcookie; | |
22a9d645 AV |
181 | |
182 | /* allow irq-off callers */ | |
183 | entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC); | |
184 | ||
185 | /* | |
186 | * If we're out of memory or if there's too much work | |
187 | * pending already, we execute synchronously. | |
188 | */ | |
083b804c | 189 | if (!entry || atomic_read(&entry_count) > MAX_WORK) { |
22a9d645 AV |
190 | kfree(entry); |
191 | spin_lock_irqsave(&async_lock, flags); | |
192 | newcookie = next_cookie++; | |
193 | spin_unlock_irqrestore(&async_lock, flags); | |
194 | ||
195 | /* low on memory.. run synchronously */ | |
196 | ptr(data, newcookie); | |
197 | return newcookie; | |
198 | } | |
083b804c | 199 | INIT_WORK(&entry->work, async_run_entry_fn); |
22a9d645 AV |
200 | entry->func = ptr; |
201 | entry->data = data; | |
202 | entry->running = running; | |
203 | ||
204 | spin_lock_irqsave(&async_lock, flags); | |
205 | newcookie = entry->cookie = next_cookie++; | |
206 | list_add_tail(&entry->list, &async_pending); | |
a4683487 DW |
207 | if (running->registered && running->count++ == 0) |
208 | list_add_tail(&running->node, &async_domains); | |
22a9d645 AV |
209 | atomic_inc(&entry_count); |
210 | spin_unlock_irqrestore(&async_lock, flags); | |
083b804c | 211 | |
774a1221 TH |
212 | /* mark that this task has queued an async job, used by module init */ |
213 | current->flags |= PF_USED_ASYNC; | |
214 | ||
083b804c TH |
215 | /* schedule for execution */ |
216 | queue_work(system_unbound_wq, &entry->work); | |
217 | ||
22a9d645 AV |
218 | return newcookie; |
219 | } | |
220 | ||
f30d5b30 CH |
221 | /** |
222 | * async_schedule - schedule a function for asynchronous execution | |
223 | * @ptr: function to execute asynchronously | |
224 | * @data: data pointer to pass to the function | |
225 | * | |
226 | * Returns an async_cookie_t that may be used for checkpointing later. | |
227 | * Note: This function may be called from atomic or non-atomic contexts. | |
228 | */ | |
22a9d645 AV |
229 | async_cookie_t async_schedule(async_func_ptr *ptr, void *data) |
230 | { | |
7a89bbc7 | 231 | return __async_schedule(ptr, data, &async_running); |
22a9d645 AV |
232 | } |
233 | EXPORT_SYMBOL_GPL(async_schedule); | |
234 | ||
f30d5b30 | 235 | /** |
766ccb9e | 236 | * async_schedule_domain - schedule a function for asynchronous execution within a certain domain |
f30d5b30 CH |
237 | * @ptr: function to execute asynchronously |
238 | * @data: data pointer to pass to the function | |
766ccb9e | 239 | * @running: running list for the domain |
f30d5b30 CH |
240 | * |
241 | * Returns an async_cookie_t that may be used for checkpointing later. | |
766ccb9e CH |
242 | * @running may be used in the async_synchronize_*_domain() functions |
243 | * to wait within a certain synchronization domain rather than globally. | |
244 | * A synchronization domain is specified via the running queue @running to use. | |
f30d5b30 CH |
245 | * Note: This function may be called from atomic or non-atomic contexts. |
246 | */ | |
766ccb9e | 247 | async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data, |
2955b47d | 248 | struct async_domain *running) |
22a9d645 AV |
249 | { |
250 | return __async_schedule(ptr, data, running); | |
251 | } | |
766ccb9e | 252 | EXPORT_SYMBOL_GPL(async_schedule_domain); |
22a9d645 | 253 | |
f30d5b30 CH |
254 | /** |
255 | * async_synchronize_full - synchronize all asynchronous function calls | |
256 | * | |
257 | * This function waits until all asynchronous function calls have been done. | |
258 | */ | |
22a9d645 AV |
259 | void async_synchronize_full(void) |
260 | { | |
a4683487 | 261 | mutex_lock(&async_register_mutex); |
33b04b93 | 262 | do { |
a4683487 DW |
263 | struct async_domain *domain = NULL; |
264 | ||
265 | spin_lock_irq(&async_lock); | |
266 | if (!list_empty(&async_domains)) | |
267 | domain = list_first_entry(&async_domains, typeof(*domain), node); | |
268 | spin_unlock_irq(&async_lock); | |
269 | ||
270 | async_synchronize_cookie_domain(next_cookie, domain); | |
271 | } while (!list_empty(&async_domains)); | |
272 | mutex_unlock(&async_register_mutex); | |
22a9d645 AV |
273 | } |
274 | EXPORT_SYMBOL_GPL(async_synchronize_full); | |
275 | ||
a4683487 DW |
276 | /** |
277 | * async_unregister_domain - ensure no more anonymous waiters on this domain | |
278 | * @domain: idle domain to flush out of any async_synchronize_full instances | |
279 | * | |
280 | * async_synchronize_{cookie|full}_domain() are not flushed since callers | |
281 | * of these routines should know the lifetime of @domain | |
282 | * | |
283 | * Prefer ASYNC_DOMAIN_EXCLUSIVE() declarations over flushing | |
284 | */ | |
285 | void async_unregister_domain(struct async_domain *domain) | |
286 | { | |
287 | mutex_lock(&async_register_mutex); | |
288 | spin_lock_irq(&async_lock); | |
289 | WARN_ON(!domain->registered || !list_empty(&domain->node) || | |
290 | !list_empty(&domain->domain)); | |
291 | domain->registered = 0; | |
292 | spin_unlock_irq(&async_lock); | |
293 | mutex_unlock(&async_register_mutex); | |
294 | } | |
295 | EXPORT_SYMBOL_GPL(async_unregister_domain); | |
296 | ||
f30d5b30 | 297 | /** |
766ccb9e | 298 | * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain |
2955b47d | 299 | * @domain: running list to synchronize on |
f30d5b30 | 300 | * |
766ccb9e | 301 | * This function waits until all asynchronous function calls for the |
2955b47d | 302 | * synchronization domain specified by the running list @domain have been done. |
f30d5b30 | 303 | */ |
2955b47d | 304 | void async_synchronize_full_domain(struct async_domain *domain) |
22a9d645 | 305 | { |
2955b47d | 306 | async_synchronize_cookie_domain(next_cookie, domain); |
22a9d645 | 307 | } |
766ccb9e | 308 | EXPORT_SYMBOL_GPL(async_synchronize_full_domain); |
22a9d645 | 309 | |
f30d5b30 | 310 | /** |
766ccb9e | 311 | * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing |
f30d5b30 CH |
312 | * @cookie: async_cookie_t to use as checkpoint |
313 | * @running: running list to synchronize on | |
314 | * | |
766ccb9e | 315 | * This function waits until all asynchronous function calls for the |
2955b47d | 316 | * synchronization domain specified by running list @running submitted |
766ccb9e | 317 | * prior to @cookie have been done. |
f30d5b30 | 318 | */ |
2955b47d | 319 | void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *running) |
22a9d645 | 320 | { |
124ff4e5 | 321 | ktime_t uninitialized_var(starttime), delta, endtime; |
22a9d645 | 322 | |
a4683487 DW |
323 | if (!running) |
324 | return; | |
325 | ||
ad160d23 | 326 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
84c15027 | 327 | printk(KERN_DEBUG "async_waiting @ %i\n", task_pid_nr(current)); |
22a9d645 AV |
328 | starttime = ktime_get(); |
329 | } | |
330 | ||
37a76bd4 | 331 | wait_event(async_done, lowest_in_progress(running) >= cookie); |
22a9d645 | 332 | |
ad160d23 | 333 | if (initcall_debug && system_state == SYSTEM_BOOTING) { |
22a9d645 AV |
334 | endtime = ktime_get(); |
335 | delta = ktime_sub(endtime, starttime); | |
336 | ||
84c15027 | 337 | printk(KERN_DEBUG "async_continuing @ %i after %lli usec\n", |
58763a29 AM |
338 | task_pid_nr(current), |
339 | (long long)ktime_to_ns(delta) >> 10); | |
22a9d645 AV |
340 | } |
341 | } | |
766ccb9e | 342 | EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain); |
22a9d645 | 343 | |
f30d5b30 CH |
344 | /** |
345 | * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing | |
346 | * @cookie: async_cookie_t to use as checkpoint | |
347 | * | |
348 | * This function waits until all asynchronous function calls prior to @cookie | |
349 | * have been done. | |
350 | */ | |
22a9d645 AV |
351 | void async_synchronize_cookie(async_cookie_t cookie) |
352 | { | |
766ccb9e | 353 | async_synchronize_cookie_domain(cookie, &async_running); |
22a9d645 AV |
354 | } |
355 | EXPORT_SYMBOL_GPL(async_synchronize_cookie); |