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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);
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}
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);