Merge remote-tracking branch 'rcu/rcu/next'
[deliverable/linux.git] / kernel / async.c
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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>
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52#include <linux/atomic.h>
53#include <linux/ktime.h>
9984de1a 54#include <linux/export.h>
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55#include <linux/wait.h>
56#include <linux/sched.h>
5a0e3ad6 57#include <linux/slab.h>
083b804c 58#include <linux/workqueue.h>
22a9d645 59
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60#include "workqueue_internal.h"
61
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62static async_cookie_t next_cookie = 1;
63
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64#define MAX_WORK 32768
65#define ASYNC_COOKIE_MAX ULLONG_MAX /* infinity cookie */
22a9d645 66
9fdb04cd 67static LIST_HEAD(async_global_pending); /* pending from all registered doms */
8723d503 68static ASYNC_DOMAIN(async_dfl_domain);
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69static DEFINE_SPINLOCK(async_lock);
70
71struct async_entry {
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72 struct list_head domain_list;
73 struct list_head global_list;
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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;
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79};
80
81static DECLARE_WAIT_QUEUE_HEAD(async_done);
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82
83static atomic_t entry_count;
22a9d645 84
8723d503 85static async_cookie_t lowest_in_progress(struct async_domain *domain)
37a76bd4 86{
92266d6e 87 struct list_head *pending;
52722794 88 async_cookie_t ret = ASYNC_COOKIE_MAX;
37a76bd4 89 unsigned long flags;
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90
91 spin_lock_irqsave(&async_lock, flags);
9fdb04cd 92
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93 if (domain)
94 pending = &domain->pending;
95 else
96 pending = &async_global_pending;
9fdb04cd 97
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98 if (!list_empty(pending))
99 ret = list_first_entry(pending, struct async_entry,
100 domain_list)->cookie;
9fdb04cd 101
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102 spin_unlock_irqrestore(&async_lock, flags);
103 return ret;
104}
083b804c 105
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106/*
107 * pick the first pending entry and run it
108 */
083b804c 109static void async_run_entry_fn(struct work_struct *work)
22a9d645 110{
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111 struct async_entry *entry =
112 container_of(work, struct async_entry, work);
22a9d645 113 unsigned long flags;
124ff4e5 114 ktime_t uninitialized_var(calltime), delta, rettime;
22a9d645 115
52722794 116 /* 1) run (and print duration) */
ad160d23 117 if (initcall_debug && system_state == SYSTEM_BOOTING) {
27fb10ed 118 pr_debug("calling %lli_%pF @ %i\n",
84c15027 119 (long long)entry->cookie,
58763a29 120 entry->func, task_pid_nr(current));
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121 calltime = ktime_get();
122 }
123 entry->func(entry->data, entry->cookie);
ad160d23 124 if (initcall_debug && system_state == SYSTEM_BOOTING) {
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125 rettime = ktime_get();
126 delta = ktime_sub(rettime, calltime);
27fb10ed 127 pr_debug("initcall %lli_%pF returned 0 after %lld usecs\n",
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128 (long long)entry->cookie,
129 entry->func,
130 (long long)ktime_to_ns(delta) >> 10);
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131 }
132
52722794 133 /* 2) remove self from the pending queues */
22a9d645 134 spin_lock_irqsave(&async_lock, flags);
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135 list_del_init(&entry->domain_list);
136 list_del_init(&entry->global_list);
22a9d645 137
52722794 138 /* 3) free the entry */
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139 kfree(entry);
140 atomic_dec(&entry_count);
141
142 spin_unlock_irqrestore(&async_lock, flags);
143
52722794 144 /* 4) wake up any waiters */
22a9d645 145 wake_up(&async_done);
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146}
147
362f2b09 148static async_cookie_t __async_schedule(async_func_t func, void *data, struct async_domain *domain)
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149{
150 struct async_entry *entry;
151 unsigned long flags;
152 async_cookie_t newcookie;
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153
154 /* allow irq-off callers */
155 entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
156
157 /*
158 * If we're out of memory or if there's too much work
159 * pending already, we execute synchronously.
160 */
083b804c 161 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
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162 kfree(entry);
163 spin_lock_irqsave(&async_lock, flags);
164 newcookie = next_cookie++;
165 spin_unlock_irqrestore(&async_lock, flags);
166
167 /* low on memory.. run synchronously */
362f2b09 168 func(data, newcookie);
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169 return newcookie;
170 }
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171 INIT_LIST_HEAD(&entry->domain_list);
172 INIT_LIST_HEAD(&entry->global_list);
083b804c 173 INIT_WORK(&entry->work, async_run_entry_fn);
362f2b09 174 entry->func = func;
22a9d645 175 entry->data = data;
8723d503 176 entry->domain = domain;
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177
178 spin_lock_irqsave(&async_lock, flags);
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179
180 /* allocate cookie and queue */
22a9d645 181 newcookie = entry->cookie = next_cookie++;
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182
183 list_add_tail(&entry->domain_list, &domain->pending);
184 if (domain->registered)
185 list_add_tail(&entry->global_list, &async_global_pending);
186
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187 atomic_inc(&entry_count);
188 spin_unlock_irqrestore(&async_lock, flags);
083b804c 189
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190 /* mark that this task has queued an async job, used by module init */
191 current->flags |= PF_USED_ASYNC;
192
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193 /* schedule for execution */
194 queue_work(system_unbound_wq, &entry->work);
195
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196 return newcookie;
197}
198
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199/**
200 * async_schedule - schedule a function for asynchronous execution
362f2b09 201 * @func: function to execute asynchronously
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202 * @data: data pointer to pass to the function
203 *
204 * Returns an async_cookie_t that may be used for checkpointing later.
205 * Note: This function may be called from atomic or non-atomic contexts.
206 */
362f2b09 207async_cookie_t async_schedule(async_func_t func, void *data)
22a9d645 208{
362f2b09 209 return __async_schedule(func, data, &async_dfl_domain);
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210}
211EXPORT_SYMBOL_GPL(async_schedule);
212
f30d5b30 213/**
766ccb9e 214 * async_schedule_domain - schedule a function for asynchronous execution within a certain domain
362f2b09 215 * @func: function to execute asynchronously
f30d5b30 216 * @data: data pointer to pass to the function
8723d503 217 * @domain: the domain
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218 *
219 * Returns an async_cookie_t that may be used for checkpointing later.
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220 * @domain may be used in the async_synchronize_*_domain() functions to
221 * wait within a certain synchronization domain rather than globally. A
222 * synchronization domain is specified via @domain. Note: This function
223 * may be called from atomic or non-atomic contexts.
f30d5b30 224 */
362f2b09 225async_cookie_t async_schedule_domain(async_func_t func, void *data,
8723d503 226 struct async_domain *domain)
22a9d645 227{
362f2b09 228 return __async_schedule(func, data, domain);
22a9d645 229}
766ccb9e 230EXPORT_SYMBOL_GPL(async_schedule_domain);
22a9d645 231
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232/**
233 * async_synchronize_full - synchronize all asynchronous function calls
234 *
235 * This function waits until all asynchronous function calls have been done.
236 */
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237void async_synchronize_full(void)
238{
9fdb04cd 239 async_synchronize_full_domain(NULL);
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240}
241EXPORT_SYMBOL_GPL(async_synchronize_full);
242
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243/**
244 * async_unregister_domain - ensure no more anonymous waiters on this domain
245 * @domain: idle domain to flush out of any async_synchronize_full instances
246 *
247 * async_synchronize_{cookie|full}_domain() are not flushed since callers
248 * of these routines should know the lifetime of @domain
249 *
250 * Prefer ASYNC_DOMAIN_EXCLUSIVE() declarations over flushing
251 */
252void async_unregister_domain(struct async_domain *domain)
253{
a4683487 254 spin_lock_irq(&async_lock);
9fdb04cd 255 WARN_ON(!domain->registered || !list_empty(&domain->pending));
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256 domain->registered = 0;
257 spin_unlock_irq(&async_lock);
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258}
259EXPORT_SYMBOL_GPL(async_unregister_domain);
260
f30d5b30 261/**
766ccb9e 262 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
8723d503 263 * @domain: the domain to synchronize
f30d5b30 264 *
766ccb9e 265 * This function waits until all asynchronous function calls for the
8723d503 266 * synchronization domain specified by @domain have been done.
f30d5b30 267 */
2955b47d 268void async_synchronize_full_domain(struct async_domain *domain)
22a9d645 269{
c68eee14 270 async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain);
22a9d645 271}
766ccb9e 272EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
22a9d645 273
f30d5b30 274/**
766ccb9e 275 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
f30d5b30 276 * @cookie: async_cookie_t to use as checkpoint
9fdb04cd 277 * @domain: the domain to synchronize (%NULL for all registered domains)
f30d5b30 278 *
766ccb9e 279 * This function waits until all asynchronous function calls for the
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280 * synchronization domain specified by @domain submitted prior to @cookie
281 * have been done.
f30d5b30 282 */
8723d503 283void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain)
22a9d645 284{
124ff4e5 285 ktime_t uninitialized_var(starttime), delta, endtime;
22a9d645 286
ad160d23 287 if (initcall_debug && system_state == SYSTEM_BOOTING) {
27fb10ed 288 pr_debug("async_waiting @ %i\n", task_pid_nr(current));
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289 starttime = ktime_get();
290 }
291
8723d503 292 wait_event(async_done, lowest_in_progress(domain) >= cookie);
22a9d645 293
ad160d23 294 if (initcall_debug && system_state == SYSTEM_BOOTING) {
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295 endtime = ktime_get();
296 delta = ktime_sub(endtime, starttime);
297
27fb10ed 298 pr_debug("async_continuing @ %i after %lli usec\n",
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299 task_pid_nr(current),
300 (long long)ktime_to_ns(delta) >> 10);
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301 }
302}
766ccb9e 303EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
22a9d645 304
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305/**
306 * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing
307 * @cookie: async_cookie_t to use as checkpoint
308 *
309 * This function waits until all asynchronous function calls prior to @cookie
310 * have been done.
311 */
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312void async_synchronize_cookie(async_cookie_t cookie)
313{
8723d503 314 async_synchronize_cookie_domain(cookie, &async_dfl_domain);
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315}
316EXPORT_SYMBOL_GPL(async_synchronize_cookie);
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317
318/**
319 * current_is_async - is %current an async worker task?
320 *
321 * Returns %true if %current is an async worker task.
322 */
323bool current_is_async(void)
324{
325 struct worker *worker = current_wq_worker();
326
327 return worker && worker->current_func == async_run_entry_fn;
328}
581da2ca 329EXPORT_SYMBOL_GPL(current_is_async);
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