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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 | 66 | |
9fdb04cd | 67 | static LIST_HEAD(async_global_pending); /* pending from all registered doms */ |
8723d503 | 68 | static ASYNC_DOMAIN(async_dfl_domain); |
22a9d645 AV |
69 | static DEFINE_SPINLOCK(async_lock); |
70 | ||
71 | struct async_entry { | |
9fdb04cd TH |
72 | struct list_head domain_list; |
73 | struct list_head global_list; | |
083b804c TH |
74 | struct work_struct work; |
75 | async_cookie_t cookie; | |
362f2b09 | 76 | async_func_t func; |
083b804c | 77 | void *data; |
8723d503 | 78 | struct async_domain *domain; |
22a9d645 AV |
79 | }; |
80 | ||
81 | static DECLARE_WAIT_QUEUE_HEAD(async_done); | |
22a9d645 AV |
82 | |
83 | static atomic_t entry_count; | |
22a9d645 | 84 | |
8723d503 | 85 | static async_cookie_t lowest_in_progress(struct async_domain *domain) |
37a76bd4 | 86 | { |
838f9cc9 | 87 | struct async_entry *first = NULL; |
52722794 | 88 | async_cookie_t ret = ASYNC_COOKIE_MAX; |
37a76bd4 | 89 | unsigned long flags; |
37a76bd4 AV |
90 | |
91 | spin_lock_irqsave(&async_lock, flags); | |
9fdb04cd | 92 | |
838f9cc9 RV |
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 | } | |
9fdb04cd | 102 | |
838f9cc9 RV |
103 | if (first) |
104 | ret = first->cookie; | |
9fdb04cd | 105 | |
37a76bd4 AV |
106 | spin_unlock_irqrestore(&async_lock, flags); |
107 | return ret; | |
108 | } | |
083b804c | 109 | |
22a9d645 AV |
110 | /* |
111 | * pick the first pending entry and run it | |
112 | */ | |
083b804c | 113 | static void async_run_entry_fn(struct work_struct *work) |
22a9d645 | 114 | { |
083b804c TH |
115 | struct async_entry *entry = |
116 | container_of(work, struct async_entry, work); | |
22a9d645 | 117 | unsigned long flags; |
124ff4e5 | 118 | ktime_t uninitialized_var(calltime), delta, rettime; |
22a9d645 | 119 | |
52722794 | 120 | /* 1) run (and print duration) */ |
b4def427 | 121 | if (initcall_debug && system_state < SYSTEM_RUNNING) { |
27fb10ed | 122 | pr_debug("calling %lli_%pF @ %i\n", |
84c15027 | 123 | (long long)entry->cookie, |
58763a29 | 124 | entry->func, task_pid_nr(current)); |
22a9d645 AV |
125 | calltime = ktime_get(); |
126 | } | |
127 | entry->func(entry->data, entry->cookie); | |
b4def427 | 128 | if (initcall_debug && system_state < SYSTEM_RUNNING) { |
22a9d645 AV |
129 | rettime = ktime_get(); |
130 | delta = ktime_sub(rettime, calltime); | |
27fb10ed | 131 | pr_debug("initcall %lli_%pF returned 0 after %lld usecs\n", |
58763a29 AM |
132 | (long long)entry->cookie, |
133 | entry->func, | |
134 | (long long)ktime_to_ns(delta) >> 10); | |
22a9d645 AV |
135 | } |
136 | ||
52722794 | 137 | /* 2) remove self from the pending queues */ |
22a9d645 | 138 | spin_lock_irqsave(&async_lock, flags); |
9fdb04cd TH |
139 | list_del_init(&entry->domain_list); |
140 | list_del_init(&entry->global_list); | |
22a9d645 | 141 | |
52722794 | 142 | /* 3) free the entry */ |
22a9d645 AV |
143 | kfree(entry); |
144 | atomic_dec(&entry_count); | |
145 | ||
146 | spin_unlock_irqrestore(&async_lock, flags); | |
147 | ||
52722794 | 148 | /* 4) wake up any waiters */ |
22a9d645 | 149 | wake_up(&async_done); |
22a9d645 AV |
150 | } |
151 | ||
362f2b09 | 152 | static async_cookie_t __async_schedule(async_func_t func, void *data, struct async_domain *domain) |
22a9d645 AV |
153 | { |
154 | struct async_entry *entry; | |
155 | unsigned long flags; | |
156 | async_cookie_t newcookie; | |
22a9d645 AV |
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 | */ | |
083b804c | 165 | if (!entry || atomic_read(&entry_count) > MAX_WORK) { |
22a9d645 AV |
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 */ | |
362f2b09 | 172 | func(data, newcookie); |
22a9d645 AV |
173 | return newcookie; |
174 | } | |
a0327ff0 JH |
175 | INIT_LIST_HEAD(&entry->domain_list); |
176 | INIT_LIST_HEAD(&entry->global_list); | |
083b804c | 177 | INIT_WORK(&entry->work, async_run_entry_fn); |
362f2b09 | 178 | entry->func = func; |
22a9d645 | 179 | entry->data = data; |
8723d503 | 180 | entry->domain = domain; |
22a9d645 AV |
181 | |
182 | spin_lock_irqsave(&async_lock, flags); | |
9fdb04cd TH |
183 | |
184 | /* allocate cookie and queue */ | |
22a9d645 | 185 | newcookie = entry->cookie = next_cookie++; |
9fdb04cd TH |
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 | ||
22a9d645 AV |
191 | atomic_inc(&entry_count); |
192 | spin_unlock_irqrestore(&async_lock, flags); | |
083b804c | 193 | |
774a1221 TH |
194 | /* mark that this task has queued an async job, used by module init */ |
195 | current->flags |= PF_USED_ASYNC; | |
196 | ||
083b804c TH |
197 | /* schedule for execution */ |
198 | queue_work(system_unbound_wq, &entry->work); | |
199 | ||
22a9d645 AV |
200 | return newcookie; |
201 | } | |
202 | ||
f30d5b30 CH |
203 | /** |
204 | * async_schedule - schedule a function for asynchronous execution | |
362f2b09 | 205 | * @func: function to execute asynchronously |
f30d5b30 CH |
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 | */ | |
362f2b09 | 211 | async_cookie_t async_schedule(async_func_t func, void *data) |
22a9d645 | 212 | { |
362f2b09 | 213 | return __async_schedule(func, data, &async_dfl_domain); |
22a9d645 AV |
214 | } |
215 | EXPORT_SYMBOL_GPL(async_schedule); | |
216 | ||
f30d5b30 | 217 | /** |
766ccb9e | 218 | * async_schedule_domain - schedule a function for asynchronous execution within a certain domain |
362f2b09 | 219 | * @func: function to execute asynchronously |
f30d5b30 | 220 | * @data: data pointer to pass to the function |
8723d503 | 221 | * @domain: the domain |
f30d5b30 CH |
222 | * |
223 | * Returns an async_cookie_t that may be used for checkpointing later. | |
8723d503 TH |
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. | |
f30d5b30 | 228 | */ |
362f2b09 | 229 | async_cookie_t async_schedule_domain(async_func_t func, void *data, |
8723d503 | 230 | struct async_domain *domain) |
22a9d645 | 231 | { |
362f2b09 | 232 | return __async_schedule(func, data, domain); |
22a9d645 | 233 | } |
766ccb9e | 234 | EXPORT_SYMBOL_GPL(async_schedule_domain); |
22a9d645 | 235 | |
f30d5b30 CH |
236 | /** |
237 | * async_synchronize_full - synchronize all asynchronous function calls | |
238 | * | |
239 | * This function waits until all asynchronous function calls have been done. | |
240 | */ | |
22a9d645 AV |
241 | void async_synchronize_full(void) |
242 | { | |
9fdb04cd | 243 | async_synchronize_full_domain(NULL); |
22a9d645 AV |
244 | } |
245 | EXPORT_SYMBOL_GPL(async_synchronize_full); | |
246 | ||
a4683487 DW |
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 | */ | |
256 | void async_unregister_domain(struct async_domain *domain) | |
257 | { | |
a4683487 | 258 | spin_lock_irq(&async_lock); |
9fdb04cd | 259 | WARN_ON(!domain->registered || !list_empty(&domain->pending)); |
a4683487 DW |
260 | domain->registered = 0; |
261 | spin_unlock_irq(&async_lock); | |
a4683487 DW |
262 | } |
263 | EXPORT_SYMBOL_GPL(async_unregister_domain); | |
264 | ||
f30d5b30 | 265 | /** |
766ccb9e | 266 | * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain |
8723d503 | 267 | * @domain: the domain to synchronize |
f30d5b30 | 268 | * |
766ccb9e | 269 | * This function waits until all asynchronous function calls for the |
8723d503 | 270 | * synchronization domain specified by @domain have been done. |
f30d5b30 | 271 | */ |
2955b47d | 272 | void async_synchronize_full_domain(struct async_domain *domain) |
22a9d645 | 273 | { |
c68eee14 | 274 | async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain); |
22a9d645 | 275 | } |
766ccb9e | 276 | EXPORT_SYMBOL_GPL(async_synchronize_full_domain); |
22a9d645 | 277 | |
f30d5b30 | 278 | /** |
766ccb9e | 279 | * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing |
f30d5b30 | 280 | * @cookie: async_cookie_t to use as checkpoint |
9fdb04cd | 281 | * @domain: the domain to synchronize (%NULL for all registered domains) |
f30d5b30 | 282 | * |
766ccb9e | 283 | * This function waits until all asynchronous function calls for the |
8723d503 TH |
284 | * synchronization domain specified by @domain submitted prior to @cookie |
285 | * have been done. | |
f30d5b30 | 286 | */ |
8723d503 | 287 | void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain) |
22a9d645 | 288 | { |
124ff4e5 | 289 | ktime_t uninitialized_var(starttime), delta, endtime; |
22a9d645 | 290 | |
b4def427 | 291 | if (initcall_debug && system_state < SYSTEM_RUNNING) { |
27fb10ed | 292 | pr_debug("async_waiting @ %i\n", task_pid_nr(current)); |
22a9d645 AV |
293 | starttime = ktime_get(); |
294 | } | |
295 | ||
8723d503 | 296 | wait_event(async_done, lowest_in_progress(domain) >= cookie); |
22a9d645 | 297 | |
b4def427 | 298 | if (initcall_debug && system_state < SYSTEM_RUNNING) { |
22a9d645 AV |
299 | endtime = ktime_get(); |
300 | delta = ktime_sub(endtime, starttime); | |
301 | ||
27fb10ed | 302 | pr_debug("async_continuing @ %i after %lli usec\n", |
58763a29 AM |
303 | task_pid_nr(current), |
304 | (long long)ktime_to_ns(delta) >> 10); | |
22a9d645 AV |
305 | } |
306 | } | |
766ccb9e | 307 | EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain); |
22a9d645 | 308 | |
f30d5b30 CH |
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 | */ | |
22a9d645 AV |
316 | void async_synchronize_cookie(async_cookie_t cookie) |
317 | { | |
8723d503 | 318 | async_synchronize_cookie_domain(cookie, &async_dfl_domain); |
22a9d645 AV |
319 | } |
320 | EXPORT_SYMBOL_GPL(async_synchronize_cookie); | |
84b233ad TH |
321 | |
322 | /** | |
323 | * current_is_async - is %current an async worker task? | |
324 | * | |
325 | * Returns %true if %current is an async worker task. | |
326 | */ | |
327 | bool current_is_async(void) | |
328 | { | |
329 | struct worker *worker = current_wq_worker(); | |
330 | ||
331 | return worker && worker->current_func == async_run_entry_fn; | |
332 | } | |
581da2ca | 333 | EXPORT_SYMBOL_GPL(current_is_async); |