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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * async.c: Asynchronous function calls for boot performance
4 *
5 * (C) Copyright 2009 Intel Corporation
6 * Author: Arjan van de Ven <arjan@linux.intel.com>
7 */
8
9
10/*
11
12Goals and Theory of Operation
13
14The primary goal of this feature is to reduce the kernel boot time,
15by doing various independent hardware delays and discovery operations
16decoupled and not strictly serialized.
17
18More specifically, the asynchronous function call concept allows
19certain operations (primarily during system boot) to happen
20asynchronously, out of order, while these operations still
21have their externally visible parts happen sequentially and in-order.
22(not unlike how out-of-order CPUs retire their instructions in order)
23
24Key to the asynchronous function call implementation is the concept of
25a "sequence cookie" (which, although it has an abstracted type, can be
26thought of as a monotonically incrementing number).
27
28The async core will assign each scheduled event such a sequence cookie and
29pass this to the called functions.
30
31The asynchronously called function should before doing a globally visible
32operation, such as registering device numbers, call the
33async_synchronize_cookie() function and pass in its own cookie. The
34async_synchronize_cookie() function will make sure that all asynchronous
35operations that were scheduled prior to the operation corresponding with the
36cookie have completed.
37
38Subsystem/driver initialization code that scheduled asynchronous probe
39functions, but which shares global resources with other drivers/subsystems
40that do not use the asynchronous call feature, need to do a full
41synchronization with the async_synchronize_full() function, before returning
42from their init function. This is to maintain strict ordering between the
43asynchronous and synchronous parts of the kernel.
44
45*/
46
47#include <linux/async.h>
48#include <linux/atomic.h>
49#include <linux/export.h>
50#include <linux/ktime.h>
51#include <linux/pid.h>
52#include <linux/sched.h>
53#include <linux/slab.h>
54#include <linux/wait.h>
55#include <linux/workqueue.h>
56
57#include "workqueue_internal.h"
58
59static async_cookie_t next_cookie = 1;
60
61#define MAX_WORK 32768
62#define ASYNC_COOKIE_MAX ULLONG_MAX /* infinity cookie */
63
64static LIST_HEAD(async_global_pending); /* pending from all registered doms */
65static ASYNC_DOMAIN(async_dfl_domain);
66static DEFINE_SPINLOCK(async_lock);
67
68struct async_entry {
69 struct list_head domain_list;
70 struct list_head global_list;
71 struct work_struct work;
72 async_cookie_t cookie;
73 async_func_t func;
74 void *data;
75 struct async_domain *domain;
76};
77
78static DECLARE_WAIT_QUEUE_HEAD(async_done);
79
80static atomic_t entry_count;
81
82static long long microseconds_since(ktime_t start)
83{
84 ktime_t now = ktime_get();
85 return ktime_to_ns(ktime_sub(now, start)) >> 10;
86}
87
88static async_cookie_t lowest_in_progress(struct async_domain *domain)
89{
90 struct async_entry *first = NULL;
91 async_cookie_t ret = ASYNC_COOKIE_MAX;
92 unsigned long flags;
93
94 spin_lock_irqsave(&async_lock, flags);
95
96 if (domain) {
97 if (!list_empty(&domain->pending))
98 first = list_first_entry(&domain->pending,
99 struct async_entry, domain_list);
100 } else {
101 if (!list_empty(&async_global_pending))
102 first = list_first_entry(&async_global_pending,
103 struct async_entry, global_list);
104 }
105
106 if (first)
107 ret = first->cookie;
108
109 spin_unlock_irqrestore(&async_lock, flags);
110 return ret;
111}
112
113/*
114 * pick the first pending entry and run it
115 */
116static void async_run_entry_fn(struct work_struct *work)
117{
118 struct async_entry *entry =
119 container_of(work, struct async_entry, work);
120 unsigned long flags;
121 ktime_t calltime;
122
123 /* 1) run (and print duration) */
124 pr_debug("calling %lli_%pS @ %i\n", (long long)entry->cookie,
125 entry->func, task_pid_nr(current));
126 calltime = ktime_get();
127
128 entry->func(entry->data, entry->cookie);
129
130 pr_debug("initcall %lli_%pS returned after %lld usecs\n",
131 (long long)entry->cookie, entry->func,
132 microseconds_since(calltime));
133
134 /* 2) remove self from the pending queues */
135 spin_lock_irqsave(&async_lock, flags);
136 list_del_init(&entry->domain_list);
137 list_del_init(&entry->global_list);
138
139 /* 3) free the entry */
140 kfree(entry);
141 atomic_dec(&entry_count);
142
143 spin_unlock_irqrestore(&async_lock, flags);
144
145 /* 4) wake up any waiters */
146 wake_up(&async_done);
147}
148
149static async_cookie_t __async_schedule_node_domain(async_func_t func,
150 void *data, int node,
151 struct async_domain *domain,
152 struct async_entry *entry)
153{
154 async_cookie_t newcookie;
155 unsigned long flags;
156
157 INIT_LIST_HEAD(&entry->domain_list);
158 INIT_LIST_HEAD(&entry->global_list);
159 INIT_WORK(&entry->work, async_run_entry_fn);
160 entry->func = func;
161 entry->data = data;
162 entry->domain = domain;
163
164 spin_lock_irqsave(&async_lock, flags);
165
166 /* allocate cookie and queue */
167 newcookie = entry->cookie = next_cookie++;
168
169 list_add_tail(&entry->domain_list, &domain->pending);
170 if (domain->registered)
171 list_add_tail(&entry->global_list, &async_global_pending);
172
173 atomic_inc(&entry_count);
174 spin_unlock_irqrestore(&async_lock, flags);
175
176 /* schedule for execution */
177 queue_work_node(node, system_unbound_wq, &entry->work);
178
179 return newcookie;
180}
181
182/**
183 * async_schedule_node_domain - NUMA specific version of async_schedule_domain
184 * @func: function to execute asynchronously
185 * @data: data pointer to pass to the function
186 * @node: NUMA node that we want to schedule this on or close to
187 * @domain: the domain
188 *
189 * Returns an async_cookie_t that may be used for checkpointing later.
190 * @domain may be used in the async_synchronize_*_domain() functions to
191 * wait within a certain synchronization domain rather than globally.
192 *
193 * Note: This function may be called from atomic or non-atomic contexts.
194 *
195 * The node requested will be honored on a best effort basis. If the node
196 * has no CPUs associated with it then the work is distributed among all
197 * available CPUs.
198 */
199async_cookie_t async_schedule_node_domain(async_func_t func, void *data,
200 int node, struct async_domain *domain)
201{
202 struct async_entry *entry;
203 unsigned long flags;
204 async_cookie_t newcookie;
205
206 /* allow irq-off callers */
207 entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
208
209 /*
210 * If we're out of memory or if there's too much work
211 * pending already, we execute synchronously.
212 */
213 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
214 kfree(entry);
215 spin_lock_irqsave(&async_lock, flags);
216 newcookie = next_cookie++;
217 spin_unlock_irqrestore(&async_lock, flags);
218
219 /* low on memory.. run synchronously */
220 func(data, newcookie);
221 return newcookie;
222 }
223
224 return __async_schedule_node_domain(func, data, node, domain, entry);
225}
226EXPORT_SYMBOL_GPL(async_schedule_node_domain);
227
228/**
229 * async_schedule_node - NUMA specific version of async_schedule
230 * @func: function to execute asynchronously
231 * @data: data pointer to pass to the function
232 * @node: NUMA node that we want to schedule this on or close to
233 *
234 * Returns an async_cookie_t that may be used for checkpointing later.
235 * Note: This function may be called from atomic or non-atomic contexts.
236 *
237 * The node requested will be honored on a best effort basis. If the node
238 * has no CPUs associated with it then the work is distributed among all
239 * available CPUs.
240 */
241async_cookie_t async_schedule_node(async_func_t func, void *data, int node)
242{
243 return async_schedule_node_domain(func, data, node, &async_dfl_domain);
244}
245EXPORT_SYMBOL_GPL(async_schedule_node);
246
247/**
248 * async_schedule_dev_nocall - A simplified variant of async_schedule_dev()
249 * @func: function to execute asynchronously
250 * @dev: device argument to be passed to function
251 *
252 * @dev is used as both the argument for the function and to provide NUMA
253 * context for where to run the function.
254 *
255 * If the asynchronous execution of @func is scheduled successfully, return
256 * true. Otherwise, do nothing and return false, unlike async_schedule_dev()
257 * that will run the function synchronously then.
258 */
259bool async_schedule_dev_nocall(async_func_t func, struct device *dev)
260{
261 struct async_entry *entry;
262
263 entry = kzalloc(sizeof(struct async_entry), GFP_KERNEL);
264
265 /* Give up if there is no memory or too much work. */
266 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
267 kfree(entry);
268 return false;
269 }
270
271 __async_schedule_node_domain(func, dev, dev_to_node(dev),
272 &async_dfl_domain, entry);
273 return true;
274}
275
276/**
277 * async_synchronize_full - synchronize all asynchronous function calls
278 *
279 * This function waits until all asynchronous function calls have been done.
280 */
281void async_synchronize_full(void)
282{
283 async_synchronize_full_domain(NULL);
284}
285EXPORT_SYMBOL_GPL(async_synchronize_full);
286
287/**
288 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
289 * @domain: the domain to synchronize
290 *
291 * This function waits until all asynchronous function calls for the
292 * synchronization domain specified by @domain have been done.
293 */
294void async_synchronize_full_domain(struct async_domain *domain)
295{
296 async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain);
297}
298EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
299
300/**
301 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
302 * @cookie: async_cookie_t to use as checkpoint
303 * @domain: the domain to synchronize (%NULL for all registered domains)
304 *
305 * This function waits until all asynchronous function calls for the
306 * synchronization domain specified by @domain submitted prior to @cookie
307 * have been done.
308 */
309void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain)
310{
311 ktime_t starttime;
312
313 pr_debug("async_waiting @ %i\n", task_pid_nr(current));
314 starttime = ktime_get();
315
316 wait_event(async_done, lowest_in_progress(domain) >= cookie);
317
318 pr_debug("async_continuing @ %i after %lli usec\n", task_pid_nr(current),
319 microseconds_since(starttime));
320}
321EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
322
323/**
324 * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing
325 * @cookie: async_cookie_t to use as checkpoint
326 *
327 * This function waits until all asynchronous function calls prior to @cookie
328 * have been done.
329 */
330void async_synchronize_cookie(async_cookie_t cookie)
331{
332 async_synchronize_cookie_domain(cookie, &async_dfl_domain);
333}
334EXPORT_SYMBOL_GPL(async_synchronize_cookie);
335
336/**
337 * current_is_async - is %current an async worker task?
338 *
339 * Returns %true if %current is an async worker task.
340 */
341bool current_is_async(void)
342{
343 struct worker *worker = current_wq_worker();
344
345 return worker && worker->current_func == async_run_entry_fn;
346}
347EXPORT_SYMBOL_GPL(current_is_async);
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>
52#include <linux/atomic.h>
53#include <linux/ktime.h>
54#include <linux/module.h>
55#include <linux/wait.h>
56#include <linux/sched.h>
57#include <linux/slab.h>
58#include <linux/workqueue.h>
59
60static async_cookie_t next_cookie = 1;
61
62#define MAX_WORK 32768
63
64static LIST_HEAD(async_pending);
65static LIST_HEAD(async_running);
66static DEFINE_SPINLOCK(async_lock);
67
68struct async_entry {
69 struct list_head list;
70 struct work_struct work;
71 async_cookie_t cookie;
72 async_func_ptr *func;
73 void *data;
74 struct list_head *running;
75};
76
77static DECLARE_WAIT_QUEUE_HEAD(async_done);
78
79static atomic_t entry_count;
80
81extern int initcall_debug;
82
83
84/*
85 * MUST be called with the lock held!
86 */
87static async_cookie_t __lowest_in_progress(struct list_head *running)
88{
89 struct async_entry *entry;
90
91 if (!list_empty(running)) {
92 entry = list_first_entry(running,
93 struct async_entry, list);
94 return entry->cookie;
95 }
96
97 list_for_each_entry(entry, &async_pending, list)
98 if (entry->running == running)
99 return entry->cookie;
100
101 return next_cookie; /* "infinity" value */
102}
103
104static async_cookie_t lowest_in_progress(struct list_head *running)
105{
106 unsigned long flags;
107 async_cookie_t ret;
108
109 spin_lock_irqsave(&async_lock, flags);
110 ret = __lowest_in_progress(running);
111 spin_unlock_irqrestore(&async_lock, flags);
112 return ret;
113}
114
115/*
116 * pick the first pending entry and run it
117 */
118static void async_run_entry_fn(struct work_struct *work)
119{
120 struct async_entry *entry =
121 container_of(work, struct async_entry, work);
122 unsigned long flags;
123 ktime_t calltime, delta, rettime;
124
125 /* 1) move self to the running queue */
126 spin_lock_irqsave(&async_lock, flags);
127 list_move_tail(&entry->list, entry->running);
128 spin_unlock_irqrestore(&async_lock, flags);
129
130 /* 2) run (and print duration) */
131 if (initcall_debug && system_state == SYSTEM_BOOTING) {
132 printk(KERN_DEBUG "calling %lli_%pF @ %i\n",
133 (long long)entry->cookie,
134 entry->func, task_pid_nr(current));
135 calltime = ktime_get();
136 }
137 entry->func(entry->data, entry->cookie);
138 if (initcall_debug && system_state == SYSTEM_BOOTING) {
139 rettime = ktime_get();
140 delta = ktime_sub(rettime, calltime);
141 printk(KERN_DEBUG "initcall %lli_%pF returned 0 after %lld usecs\n",
142 (long long)entry->cookie,
143 entry->func,
144 (long long)ktime_to_ns(delta) >> 10);
145 }
146
147 /* 3) remove self from the running queue */
148 spin_lock_irqsave(&async_lock, flags);
149 list_del(&entry->list);
150
151 /* 4) free the entry */
152 kfree(entry);
153 atomic_dec(&entry_count);
154
155 spin_unlock_irqrestore(&async_lock, flags);
156
157 /* 5) wake up any waiters */
158 wake_up(&async_done);
159}
160
161static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct list_head *running)
162{
163 struct async_entry *entry;
164 unsigned long flags;
165 async_cookie_t newcookie;
166
167 /* allow irq-off callers */
168 entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
169
170 /*
171 * If we're out of memory or if there's too much work
172 * pending already, we execute synchronously.
173 */
174 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
175 kfree(entry);
176 spin_lock_irqsave(&async_lock, flags);
177 newcookie = next_cookie++;
178 spin_unlock_irqrestore(&async_lock, flags);
179
180 /* low on memory.. run synchronously */
181 ptr(data, newcookie);
182 return newcookie;
183 }
184 INIT_WORK(&entry->work, async_run_entry_fn);
185 entry->func = ptr;
186 entry->data = data;
187 entry->running = running;
188
189 spin_lock_irqsave(&async_lock, flags);
190 newcookie = entry->cookie = next_cookie++;
191 list_add_tail(&entry->list, &async_pending);
192 atomic_inc(&entry_count);
193 spin_unlock_irqrestore(&async_lock, flags);
194
195 /* schedule for execution */
196 queue_work(system_unbound_wq, &entry->work);
197
198 return newcookie;
199}
200
201/**
202 * async_schedule - schedule a function for asynchronous execution
203 * @ptr: function to execute asynchronously
204 * @data: data pointer to pass to the function
205 *
206 * Returns an async_cookie_t that may be used for checkpointing later.
207 * Note: This function may be called from atomic or non-atomic contexts.
208 */
209async_cookie_t async_schedule(async_func_ptr *ptr, void *data)
210{
211 return __async_schedule(ptr, data, &async_running);
212}
213EXPORT_SYMBOL_GPL(async_schedule);
214
215/**
216 * async_schedule_domain - schedule a function for asynchronous execution within a certain domain
217 * @ptr: function to execute asynchronously
218 * @data: data pointer to pass to the function
219 * @running: running list for the domain
220 *
221 * Returns an async_cookie_t that may be used for checkpointing later.
222 * @running may be used in the async_synchronize_*_domain() functions
223 * to wait within a certain synchronization domain rather than globally.
224 * A synchronization domain is specified via the running queue @running to use.
225 * Note: This function may be called from atomic or non-atomic contexts.
226 */
227async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data,
228 struct list_head *running)
229{
230 return __async_schedule(ptr, data, running);
231}
232EXPORT_SYMBOL_GPL(async_schedule_domain);
233
234/**
235 * async_synchronize_full - synchronize all asynchronous function calls
236 *
237 * This function waits until all asynchronous function calls have been done.
238 */
239void async_synchronize_full(void)
240{
241 do {
242 async_synchronize_cookie(next_cookie);
243 } while (!list_empty(&async_running) || !list_empty(&async_pending));
244}
245EXPORT_SYMBOL_GPL(async_synchronize_full);
246
247/**
248 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
249 * @list: running list to synchronize on
250 *
251 * This function waits until all asynchronous function calls for the
252 * synchronization domain specified by the running list @list have been done.
253 */
254void async_synchronize_full_domain(struct list_head *list)
255{
256 async_synchronize_cookie_domain(next_cookie, list);
257}
258EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
259
260/**
261 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
262 * @cookie: async_cookie_t to use as checkpoint
263 * @running: running list to synchronize on
264 *
265 * This function waits until all asynchronous function calls for the
266 * synchronization domain specified by the running list @list submitted
267 * prior to @cookie have been done.
268 */
269void async_synchronize_cookie_domain(async_cookie_t cookie,
270 struct list_head *running)
271{
272 ktime_t starttime, delta, endtime;
273
274 if (initcall_debug && system_state == SYSTEM_BOOTING) {
275 printk(KERN_DEBUG "async_waiting @ %i\n", task_pid_nr(current));
276 starttime = ktime_get();
277 }
278
279 wait_event(async_done, lowest_in_progress(running) >= cookie);
280
281 if (initcall_debug && system_state == SYSTEM_BOOTING) {
282 endtime = ktime_get();
283 delta = ktime_sub(endtime, starttime);
284
285 printk(KERN_DEBUG "async_continuing @ %i after %lli usec\n",
286 task_pid_nr(current),
287 (long long)ktime_to_ns(delta) >> 10);
288 }
289}
290EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
291
292/**
293 * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing
294 * @cookie: async_cookie_t to use as checkpoint
295 *
296 * This function waits until all asynchronous function calls prior to @cookie
297 * have been done.
298 */
299void async_synchronize_cookie(async_cookie_t cookie)
300{
301 async_synchronize_cookie_domain(cookie, &async_running);
302}
303EXPORT_SYMBOL_GPL(async_synchronize_cookie);