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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/ktime.h>
50#include <linux/export.h>
51#include <linux/wait.h>
52#include <linux/sched.h>
53#include <linux/slab.h>
54#include <linux/workqueue.h>
55
56#include "workqueue_internal.h"
57
58static async_cookie_t next_cookie = 1;
59
60#define MAX_WORK 32768
61#define ASYNC_COOKIE_MAX ULLONG_MAX /* infinity cookie */
62
63static LIST_HEAD(async_global_pending); /* pending from all registered doms */
64static ASYNC_DOMAIN(async_dfl_domain);
65static DEFINE_SPINLOCK(async_lock);
66
67struct async_entry {
68 struct list_head domain_list;
69 struct list_head global_list;
70 struct work_struct work;
71 async_cookie_t cookie;
72 async_func_t func;
73 void *data;
74 struct async_domain *domain;
75};
76
77static DECLARE_WAIT_QUEUE_HEAD(async_done);
78
79static atomic_t entry_count;
80
81static long long microseconds_since(ktime_t start)
82{
83 ktime_t now = ktime_get();
84 return ktime_to_ns(ktime_sub(now, start)) >> 10;
85}
86
87static async_cookie_t lowest_in_progress(struct async_domain *domain)
88{
89 struct async_entry *first = NULL;
90 async_cookie_t ret = ASYNC_COOKIE_MAX;
91 unsigned long flags;
92
93 spin_lock_irqsave(&async_lock, flags);
94
95 if (domain) {
96 if (!list_empty(&domain->pending))
97 first = list_first_entry(&domain->pending,
98 struct async_entry, domain_list);
99 } else {
100 if (!list_empty(&async_global_pending))
101 first = list_first_entry(&async_global_pending,
102 struct async_entry, global_list);
103 }
104
105 if (first)
106 ret = first->cookie;
107
108 spin_unlock_irqrestore(&async_lock, flags);
109 return ret;
110}
111
112/*
113 * pick the first pending entry and run it
114 */
115static void async_run_entry_fn(struct work_struct *work)
116{
117 struct async_entry *entry =
118 container_of(work, struct async_entry, work);
119 unsigned long flags;
120 ktime_t calltime;
121
122 /* 1) run (and print duration) */
123 pr_debug("calling %lli_%pS @ %i\n", (long long)entry->cookie,
124 entry->func, task_pid_nr(current));
125 calltime = ktime_get();
126
127 entry->func(entry->data, entry->cookie);
128
129 pr_debug("initcall %lli_%pS returned after %lld usecs\n",
130 (long long)entry->cookie, entry->func,
131 microseconds_since(calltime));
132
133 /* 2) remove self from the pending queues */
134 spin_lock_irqsave(&async_lock, flags);
135 list_del_init(&entry->domain_list);
136 list_del_init(&entry->global_list);
137
138 /* 3) free the entry */
139 kfree(entry);
140 atomic_dec(&entry_count);
141
142 spin_unlock_irqrestore(&async_lock, flags);
143
144 /* 4) wake up any waiters */
145 wake_up(&async_done);
146}
147
148/**
149 * async_schedule_node_domain - NUMA specific version of async_schedule_domain
150 * @func: function to execute asynchronously
151 * @data: data pointer to pass to the function
152 * @node: NUMA node that we want to schedule this on or close to
153 * @domain: the domain
154 *
155 * Returns an async_cookie_t that may be used for checkpointing later.
156 * @domain may be used in the async_synchronize_*_domain() functions to
157 * wait within a certain synchronization domain rather than globally.
158 *
159 * Note: This function may be called from atomic or non-atomic contexts.
160 *
161 * The node requested will be honored on a best effort basis. If the node
162 * has no CPUs associated with it then the work is distributed among all
163 * available CPUs.
164 */
165async_cookie_t async_schedule_node_domain(async_func_t func, void *data,
166 int node, struct async_domain *domain)
167{
168 struct async_entry *entry;
169 unsigned long flags;
170 async_cookie_t newcookie;
171
172 /* allow irq-off callers */
173 entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
174
175 /*
176 * If we're out of memory or if there's too much work
177 * pending already, we execute synchronously.
178 */
179 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
180 kfree(entry);
181 spin_lock_irqsave(&async_lock, flags);
182 newcookie = next_cookie++;
183 spin_unlock_irqrestore(&async_lock, flags);
184
185 /* low on memory.. run synchronously */
186 func(data, newcookie);
187 return newcookie;
188 }
189 INIT_LIST_HEAD(&entry->domain_list);
190 INIT_LIST_HEAD(&entry->global_list);
191 INIT_WORK(&entry->work, async_run_entry_fn);
192 entry->func = func;
193 entry->data = data;
194 entry->domain = domain;
195
196 spin_lock_irqsave(&async_lock, flags);
197
198 /* allocate cookie and queue */
199 newcookie = entry->cookie = next_cookie++;
200
201 list_add_tail(&entry->domain_list, &domain->pending);
202 if (domain->registered)
203 list_add_tail(&entry->global_list, &async_global_pending);
204
205 atomic_inc(&entry_count);
206 spin_unlock_irqrestore(&async_lock, flags);
207
208 /* schedule for execution */
209 queue_work_node(node, system_unbound_wq, &entry->work);
210
211 return newcookie;
212}
213EXPORT_SYMBOL_GPL(async_schedule_node_domain);
214
215/**
216 * async_schedule_node - NUMA specific version of async_schedule
217 * @func: function to execute asynchronously
218 * @data: data pointer to pass to the function
219 * @node: NUMA node that we want to schedule this on or close to
220 *
221 * Returns an async_cookie_t that may be used for checkpointing later.
222 * Note: This function may be called from atomic or non-atomic contexts.
223 *
224 * The node requested will be honored on a best effort basis. If the node
225 * has no CPUs associated with it then the work is distributed among all
226 * available CPUs.
227 */
228async_cookie_t async_schedule_node(async_func_t func, void *data, int node)
229{
230 return async_schedule_node_domain(func, data, node, &async_dfl_domain);
231}
232EXPORT_SYMBOL_GPL(async_schedule_node);
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 async_synchronize_full_domain(NULL);
242}
243EXPORT_SYMBOL_GPL(async_synchronize_full);
244
245/**
246 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
247 * @domain: the domain to synchronize
248 *
249 * This function waits until all asynchronous function calls for the
250 * synchronization domain specified by @domain have been done.
251 */
252void async_synchronize_full_domain(struct async_domain *domain)
253{
254 async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain);
255}
256EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
257
258/**
259 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
260 * @cookie: async_cookie_t to use as checkpoint
261 * @domain: the domain to synchronize (%NULL for all registered domains)
262 *
263 * This function waits until all asynchronous function calls for the
264 * synchronization domain specified by @domain submitted prior to @cookie
265 * have been done.
266 */
267void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain)
268{
269 ktime_t starttime;
270
271 pr_debug("async_waiting @ %i\n", task_pid_nr(current));
272 starttime = ktime_get();
273
274 wait_event(async_done, lowest_in_progress(domain) >= cookie);
275
276 pr_debug("async_continuing @ %i after %lli usec\n", task_pid_nr(current),
277 microseconds_since(starttime));
278}
279EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
280
281/**
282 * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing
283 * @cookie: async_cookie_t to use as checkpoint
284 *
285 * This function waits until all asynchronous function calls prior to @cookie
286 * have been done.
287 */
288void async_synchronize_cookie(async_cookie_t cookie)
289{
290 async_synchronize_cookie_domain(cookie, &async_dfl_domain);
291}
292EXPORT_SYMBOL_GPL(async_synchronize_cookie);
293
294/**
295 * current_is_async - is %current an async worker task?
296 *
297 * Returns %true if %current is an async worker task.
298 */
299bool current_is_async(void)
300{
301 struct worker *worker = current_wq_worker();
302
303 return worker && worker->current_func == async_run_entry_fn;
304}
305EXPORT_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);
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);