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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>
52#include <linux/atomic.h>
53#include <linux/ktime.h>
54#include <linux/export.h>
55#include <linux/wait.h>
56#include <linux/sched.h>
57#include <linux/slab.h>
58#include <linux/workqueue.h>
59
60#include "workqueue_internal.h"
61
62static async_cookie_t next_cookie = 1;
63
64#define MAX_WORK 32768
65#define ASYNC_COOKIE_MAX ULLONG_MAX /* infinity cookie */
66
67static LIST_HEAD(async_global_pending); /* pending from all registered doms */
68static ASYNC_DOMAIN(async_dfl_domain);
69static DEFINE_SPINLOCK(async_lock);
70
71struct async_entry {
72 struct list_head domain_list;
73 struct list_head global_list;
74 struct work_struct work;
75 async_cookie_t cookie;
76 async_func_t func;
77 void *data;
78 struct async_domain *domain;
79};
80
81static DECLARE_WAIT_QUEUE_HEAD(async_done);
82
83static atomic_t entry_count;
84
85static async_cookie_t lowest_in_progress(struct async_domain *domain)
86{
87 struct async_entry *first = NULL;
88 async_cookie_t ret = ASYNC_COOKIE_MAX;
89 unsigned long flags;
90
91 spin_lock_irqsave(&async_lock, flags);
92
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 }
102
103 if (first)
104 ret = first->cookie;
105
106 spin_unlock_irqrestore(&async_lock, flags);
107 return ret;
108}
109
110/*
111 * pick the first pending entry and run it
112 */
113static void async_run_entry_fn(struct work_struct *work)
114{
115 struct async_entry *entry =
116 container_of(work, struct async_entry, work);
117 unsigned long flags;
118 ktime_t uninitialized_var(calltime), delta, rettime;
119
120 /* 1) run (and print duration) */
121 if (initcall_debug && system_state < SYSTEM_RUNNING) {
122 pr_debug("calling %lli_%pF @ %i\n",
123 (long long)entry->cookie,
124 entry->func, task_pid_nr(current));
125 calltime = ktime_get();
126 }
127 entry->func(entry->data, entry->cookie);
128 if (initcall_debug && system_state < SYSTEM_RUNNING) {
129 rettime = ktime_get();
130 delta = ktime_sub(rettime, calltime);
131 pr_debug("initcall %lli_%pF returned 0 after %lld usecs\n",
132 (long long)entry->cookie,
133 entry->func,
134 (long long)ktime_to_ns(delta) >> 10);
135 }
136
137 /* 2) remove self from the pending queues */
138 spin_lock_irqsave(&async_lock, flags);
139 list_del_init(&entry->domain_list);
140 list_del_init(&entry->global_list);
141
142 /* 3) free the entry */
143 kfree(entry);
144 atomic_dec(&entry_count);
145
146 spin_unlock_irqrestore(&async_lock, flags);
147
148 /* 4) wake up any waiters */
149 wake_up(&async_done);
150}
151
152static async_cookie_t __async_schedule(async_func_t func, void *data, struct async_domain *domain)
153{
154 struct async_entry *entry;
155 unsigned long flags;
156 async_cookie_t newcookie;
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 */
165 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
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 */
172 func(data, newcookie);
173 return newcookie;
174 }
175 INIT_LIST_HEAD(&entry->domain_list);
176 INIT_LIST_HEAD(&entry->global_list);
177 INIT_WORK(&entry->work, async_run_entry_fn);
178 entry->func = func;
179 entry->data = data;
180 entry->domain = domain;
181
182 spin_lock_irqsave(&async_lock, flags);
183
184 /* allocate cookie and queue */
185 newcookie = entry->cookie = next_cookie++;
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
191 atomic_inc(&entry_count);
192 spin_unlock_irqrestore(&async_lock, flags);
193
194 /* mark that this task has queued an async job, used by module init */
195 current->flags |= PF_USED_ASYNC;
196
197 /* schedule for execution */
198 queue_work(system_unbound_wq, &entry->work);
199
200 return newcookie;
201}
202
203/**
204 * async_schedule - schedule a function for asynchronous execution
205 * @func: function to execute asynchronously
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 */
211async_cookie_t async_schedule(async_func_t func, void *data)
212{
213 return __async_schedule(func, data, &async_dfl_domain);
214}
215EXPORT_SYMBOL_GPL(async_schedule);
216
217/**
218 * async_schedule_domain - schedule a function for asynchronous execution within a certain domain
219 * @func: function to execute asynchronously
220 * @data: data pointer to pass to the function
221 * @domain: the domain
222 *
223 * Returns an async_cookie_t that may be used for checkpointing later.
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.
228 */
229async_cookie_t async_schedule_domain(async_func_t func, void *data,
230 struct async_domain *domain)
231{
232 return __async_schedule(func, data, domain);
233}
234EXPORT_SYMBOL_GPL(async_schedule_domain);
235
236/**
237 * async_synchronize_full - synchronize all asynchronous function calls
238 *
239 * This function waits until all asynchronous function calls have been done.
240 */
241void async_synchronize_full(void)
242{
243 async_synchronize_full_domain(NULL);
244}
245EXPORT_SYMBOL_GPL(async_synchronize_full);
246
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 */
256void async_unregister_domain(struct async_domain *domain)
257{
258 spin_lock_irq(&async_lock);
259 WARN_ON(!domain->registered || !list_empty(&domain->pending));
260 domain->registered = 0;
261 spin_unlock_irq(&async_lock);
262}
263EXPORT_SYMBOL_GPL(async_unregister_domain);
264
265/**
266 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
267 * @domain: the domain to synchronize
268 *
269 * This function waits until all asynchronous function calls for the
270 * synchronization domain specified by @domain have been done.
271 */
272void async_synchronize_full_domain(struct async_domain *domain)
273{
274 async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain);
275}
276EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
277
278/**
279 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
280 * @cookie: async_cookie_t to use as checkpoint
281 * @domain: the domain to synchronize (%NULL for all registered domains)
282 *
283 * This function waits until all asynchronous function calls for the
284 * synchronization domain specified by @domain submitted prior to @cookie
285 * have been done.
286 */
287void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain)
288{
289 ktime_t uninitialized_var(starttime), delta, endtime;
290
291 if (initcall_debug && system_state < SYSTEM_RUNNING) {
292 pr_debug("async_waiting @ %i\n", task_pid_nr(current));
293 starttime = ktime_get();
294 }
295
296 wait_event(async_done, lowest_in_progress(domain) >= cookie);
297
298 if (initcall_debug && system_state < SYSTEM_RUNNING) {
299 endtime = ktime_get();
300 delta = ktime_sub(endtime, starttime);
301
302 pr_debug("async_continuing @ %i after %lli usec\n",
303 task_pid_nr(current),
304 (long long)ktime_to_ns(delta) >> 10);
305 }
306}
307EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
308
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 */
316void async_synchronize_cookie(async_cookie_t cookie)
317{
318 async_synchronize_cookie_domain(cookie, &async_dfl_domain);
319}
320EXPORT_SYMBOL_GPL(async_synchronize_cookie);
321
322/**
323 * current_is_async - is %current an async worker task?
324 *
325 * Returns %true if %current is an async worker task.
326 */
327bool current_is_async(void)
328{
329 struct worker *worker = current_wq_worker();
330
331 return worker && worker->current_func == async_run_entry_fn;
332}
333EXPORT_SYMBOL_GPL(current_is_async);
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);
67static struct workqueue_struct *async_wq;
68
69struct async_entry {
70 struct list_head domain_list;
71 struct list_head global_list;
72 struct work_struct work;
73 async_cookie_t cookie;
74 async_func_t func;
75 void *data;
76 struct async_domain *domain;
77};
78
79static DECLARE_WAIT_QUEUE_HEAD(async_done);
80
81static atomic_t entry_count;
82
83static long long microseconds_since(ktime_t start)
84{
85 ktime_t now = ktime_get();
86 return ktime_to_ns(ktime_sub(now, start)) >> 10;
87}
88
89static async_cookie_t lowest_in_progress(struct async_domain *domain)
90{
91 struct async_entry *first = NULL;
92 async_cookie_t ret = ASYNC_COOKIE_MAX;
93 unsigned long flags;
94
95 spin_lock_irqsave(&async_lock, flags);
96
97 if (domain) {
98 if (!list_empty(&domain->pending))
99 first = list_first_entry(&domain->pending,
100 struct async_entry, domain_list);
101 } else {
102 if (!list_empty(&async_global_pending))
103 first = list_first_entry(&async_global_pending,
104 struct async_entry, global_list);
105 }
106
107 if (first)
108 ret = first->cookie;
109
110 spin_unlock_irqrestore(&async_lock, flags);
111 return ret;
112}
113
114/*
115 * pick the first pending entry and run it
116 */
117static void async_run_entry_fn(struct work_struct *work)
118{
119 struct async_entry *entry =
120 container_of(work, struct async_entry, work);
121 unsigned long flags;
122 ktime_t calltime;
123
124 /* 1) run (and print duration) */
125 pr_debug("calling %lli_%pS @ %i\n", (long long)entry->cookie,
126 entry->func, task_pid_nr(current));
127 calltime = ktime_get();
128
129 entry->func(entry->data, entry->cookie);
130
131 pr_debug("initcall %lli_%pS returned after %lld usecs\n",
132 (long long)entry->cookie, entry->func,
133 microseconds_since(calltime));
134
135 /* 2) remove self from the pending queues */
136 spin_lock_irqsave(&async_lock, flags);
137 list_del_init(&entry->domain_list);
138 list_del_init(&entry->global_list);
139
140 /* 3) free the entry */
141 kfree(entry);
142 atomic_dec(&entry_count);
143
144 spin_unlock_irqrestore(&async_lock, flags);
145
146 /* 4) wake up any waiters */
147 wake_up(&async_done);
148}
149
150static async_cookie_t __async_schedule_node_domain(async_func_t func,
151 void *data, int node,
152 struct async_domain *domain,
153 struct async_entry *entry)
154{
155 async_cookie_t newcookie;
156 unsigned long flags;
157
158 INIT_LIST_HEAD(&entry->domain_list);
159 INIT_LIST_HEAD(&entry->global_list);
160 INIT_WORK(&entry->work, async_run_entry_fn);
161 entry->func = func;
162 entry->data = data;
163 entry->domain = domain;
164
165 spin_lock_irqsave(&async_lock, flags);
166
167 /* allocate cookie and queue */
168 newcookie = entry->cookie = next_cookie++;
169
170 list_add_tail(&entry->domain_list, &domain->pending);
171 if (domain->registered)
172 list_add_tail(&entry->global_list, &async_global_pending);
173
174 atomic_inc(&entry_count);
175 spin_unlock_irqrestore(&async_lock, flags);
176
177 /* schedule for execution */
178 queue_work_node(node, async_wq, &entry->work);
179
180 return newcookie;
181}
182
183/**
184 * async_schedule_node_domain - NUMA specific version of async_schedule_domain
185 * @func: function to execute asynchronously
186 * @data: data pointer to pass to the function
187 * @node: NUMA node that we want to schedule this on or close to
188 * @domain: the domain
189 *
190 * Returns an async_cookie_t that may be used for checkpointing later.
191 * @domain may be used in the async_synchronize_*_domain() functions to
192 * wait within a certain synchronization domain rather than globally.
193 *
194 * Note: This function may be called from atomic or non-atomic contexts.
195 *
196 * The node requested will be honored on a best effort basis. If the node
197 * has no CPUs associated with it then the work is distributed among all
198 * available CPUs.
199 */
200async_cookie_t async_schedule_node_domain(async_func_t func, void *data,
201 int node, struct async_domain *domain)
202{
203 struct async_entry *entry;
204 unsigned long flags;
205 async_cookie_t newcookie;
206
207 /* allow irq-off callers */
208 entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
209
210 /*
211 * If we're out of memory or if there's too much work
212 * pending already, we execute synchronously.
213 */
214 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
215 kfree(entry);
216 spin_lock_irqsave(&async_lock, flags);
217 newcookie = next_cookie++;
218 spin_unlock_irqrestore(&async_lock, flags);
219
220 /* low on memory.. run synchronously */
221 func(data, newcookie);
222 return newcookie;
223 }
224
225 return __async_schedule_node_domain(func, data, node, domain, entry);
226}
227EXPORT_SYMBOL_GPL(async_schedule_node_domain);
228
229/**
230 * async_schedule_node - NUMA specific version of async_schedule
231 * @func: function to execute asynchronously
232 * @data: data pointer to pass to the function
233 * @node: NUMA node that we want to schedule this on or close to
234 *
235 * Returns an async_cookie_t that may be used for checkpointing later.
236 * Note: This function may be called from atomic or non-atomic contexts.
237 *
238 * The node requested will be honored on a best effort basis. If the node
239 * has no CPUs associated with it then the work is distributed among all
240 * available CPUs.
241 */
242async_cookie_t async_schedule_node(async_func_t func, void *data, int node)
243{
244 return async_schedule_node_domain(func, data, node, &async_dfl_domain);
245}
246EXPORT_SYMBOL_GPL(async_schedule_node);
247
248/**
249 * async_schedule_dev_nocall - A simplified variant of async_schedule_dev()
250 * @func: function to execute asynchronously
251 * @dev: device argument to be passed to function
252 *
253 * @dev is used as both the argument for the function and to provide NUMA
254 * context for where to run the function.
255 *
256 * If the asynchronous execution of @func is scheduled successfully, return
257 * true. Otherwise, do nothing and return false, unlike async_schedule_dev()
258 * that will run the function synchronously then.
259 */
260bool async_schedule_dev_nocall(async_func_t func, struct device *dev)
261{
262 struct async_entry *entry;
263
264 entry = kzalloc(sizeof(struct async_entry), GFP_KERNEL);
265
266 /* Give up if there is no memory or too much work. */
267 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
268 kfree(entry);
269 return false;
270 }
271
272 __async_schedule_node_domain(func, dev, dev_to_node(dev),
273 &async_dfl_domain, entry);
274 return true;
275}
276
277/**
278 * async_synchronize_full - synchronize all asynchronous function calls
279 *
280 * This function waits until all asynchronous function calls have been done.
281 */
282void async_synchronize_full(void)
283{
284 async_synchronize_full_domain(NULL);
285}
286EXPORT_SYMBOL_GPL(async_synchronize_full);
287
288/**
289 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
290 * @domain: the domain to synchronize
291 *
292 * This function waits until all asynchronous function calls for the
293 * synchronization domain specified by @domain have been done.
294 */
295void async_synchronize_full_domain(struct async_domain *domain)
296{
297 async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain);
298}
299EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
300
301/**
302 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
303 * @cookie: async_cookie_t to use as checkpoint
304 * @domain: the domain to synchronize (%NULL for all registered domains)
305 *
306 * This function waits until all asynchronous function calls for the
307 * synchronization domain specified by @domain submitted prior to @cookie
308 * have been done.
309 */
310void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain)
311{
312 ktime_t starttime;
313
314 pr_debug("async_waiting @ %i\n", task_pid_nr(current));
315 starttime = ktime_get();
316
317 wait_event(async_done, lowest_in_progress(domain) >= cookie);
318
319 pr_debug("async_continuing @ %i after %lli usec\n", task_pid_nr(current),
320 microseconds_since(starttime));
321}
322EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
323
324/**
325 * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing
326 * @cookie: async_cookie_t to use as checkpoint
327 *
328 * This function waits until all asynchronous function calls prior to @cookie
329 * have been done.
330 */
331void async_synchronize_cookie(async_cookie_t cookie)
332{
333 async_synchronize_cookie_domain(cookie, &async_dfl_domain);
334}
335EXPORT_SYMBOL_GPL(async_synchronize_cookie);
336
337/**
338 * current_is_async - is %current an async worker task?
339 *
340 * Returns %true if %current is an async worker task.
341 */
342bool current_is_async(void)
343{
344 struct worker *worker = current_wq_worker();
345
346 return worker && worker->current_func == async_run_entry_fn;
347}
348EXPORT_SYMBOL_GPL(current_is_async);
349
350void __init async_init(void)
351{
352 /*
353 * Async can schedule a number of interdependent work items. However,
354 * unbound workqueues can handle only upto min_active interdependent
355 * work items. The default min_active of 8 isn't sufficient for async
356 * and can lead to stalls. Let's use a dedicated workqueue with raised
357 * min_active.
358 */
359 async_wq = alloc_workqueue("async", WQ_UNBOUND, 0);
360 BUG_ON(!async_wq);
361 workqueue_set_min_active(async_wq, WQ_DFL_ACTIVE);
362}