Loading...
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/*
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
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
81
82/*
83 * MUST be called with the lock held!
84 */
85static async_cookie_t __lowest_in_progress(struct list_head *running)
86{
87 struct async_entry *entry;
88
89 if (!running) { /* just check the entry count */
90 if (atomic_read(&entry_count))
91 return 0; /* smaller than any cookie */
92 else
93 return next_cookie;
94 }
95
96 if (!list_empty(running)) {
97 entry = list_first_entry(running,
98 struct async_entry, list);
99 return entry->cookie;
100 }
101
102 list_for_each_entry(entry, &async_pending, list)
103 if (entry->running == running)
104 return entry->cookie;
105
106 return next_cookie; /* "infinity" value */
107}
108
109static async_cookie_t lowest_in_progress(struct list_head *running)
110{
111 unsigned long flags;
112 async_cookie_t ret;
113
114 spin_lock_irqsave(&async_lock, flags);
115 ret = __lowest_in_progress(running);
116 spin_unlock_irqrestore(&async_lock, flags);
117 return ret;
118}
119
120/*
121 * pick the first pending entry and run it
122 */
123static void async_run_entry_fn(struct work_struct *work)
124{
125 struct async_entry *entry =
126 container_of(work, struct async_entry, work);
127 unsigned long flags;
128 ktime_t uninitialized_var(calltime), delta, rettime;
129
130 /* 1) move self to the running queue */
131 spin_lock_irqsave(&async_lock, flags);
132 list_move_tail(&entry->list, entry->running);
133 spin_unlock_irqrestore(&async_lock, flags);
134
135 /* 2) run (and print duration) */
136 if (initcall_debug && system_state == SYSTEM_BOOTING) {
137 printk(KERN_DEBUG "calling %lli_%pF @ %i\n",
138 (long long)entry->cookie,
139 entry->func, task_pid_nr(current));
140 calltime = ktime_get();
141 }
142 entry->func(entry->data, entry->cookie);
143 if (initcall_debug && system_state == SYSTEM_BOOTING) {
144 rettime = ktime_get();
145 delta = ktime_sub(rettime, calltime);
146 printk(KERN_DEBUG "initcall %lli_%pF returned 0 after %lld usecs\n",
147 (long long)entry->cookie,
148 entry->func,
149 (long long)ktime_to_ns(delta) >> 10);
150 }
151
152 /* 3) remove self from the running queue */
153 spin_lock_irqsave(&async_lock, flags);
154 list_del(&entry->list);
155
156 /* 4) free the entry */
157 kfree(entry);
158 atomic_dec(&entry_count);
159
160 spin_unlock_irqrestore(&async_lock, flags);
161
162 /* 5) wake up any waiters */
163 wake_up(&async_done);
164}
165
166static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct list_head *running)
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 ptr(data, newcookie);
187 return newcookie;
188 }
189 INIT_WORK(&entry->work, async_run_entry_fn);
190 entry->func = ptr;
191 entry->data = data;
192 entry->running = running;
193
194 spin_lock_irqsave(&async_lock, flags);
195 newcookie = entry->cookie = next_cookie++;
196 list_add_tail(&entry->list, &async_pending);
197 atomic_inc(&entry_count);
198 spin_unlock_irqrestore(&async_lock, flags);
199
200 /* schedule for execution */
201 queue_work(system_unbound_wq, &entry->work);
202
203 return newcookie;
204}
205
206/**
207 * async_schedule - schedule a function for asynchronous execution
208 * @ptr: function to execute asynchronously
209 * @data: data pointer to pass to the function
210 *
211 * Returns an async_cookie_t that may be used for checkpointing later.
212 * Note: This function may be called from atomic or non-atomic contexts.
213 */
214async_cookie_t async_schedule(async_func_ptr *ptr, void *data)
215{
216 return __async_schedule(ptr, data, &async_running);
217}
218EXPORT_SYMBOL_GPL(async_schedule);
219
220/**
221 * async_schedule_domain - schedule a function for asynchronous execution within a certain domain
222 * @ptr: function to execute asynchronously
223 * @data: data pointer to pass to the function
224 * @running: running list for the domain
225 *
226 * Returns an async_cookie_t that may be used for checkpointing later.
227 * @running may be used in the async_synchronize_*_domain() functions
228 * to wait within a certain synchronization domain rather than globally.
229 * A synchronization domain is specified via the running queue @running to use.
230 * Note: This function may be called from atomic or non-atomic contexts.
231 */
232async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data,
233 struct list_head *running)
234{
235 return __async_schedule(ptr, data, running);
236}
237EXPORT_SYMBOL_GPL(async_schedule_domain);
238
239/**
240 * async_synchronize_full - synchronize all asynchronous function calls
241 *
242 * This function waits until all asynchronous function calls have been done.
243 */
244void async_synchronize_full(void)
245{
246 async_synchronize_cookie_domain(next_cookie, NULL);
247}
248EXPORT_SYMBOL_GPL(async_synchronize_full);
249
250/**
251 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
252 * @list: running list to synchronize on
253 *
254 * This function waits until all asynchronous function calls for the
255 * synchronization domain specified by the running list @list have been done.
256 */
257void async_synchronize_full_domain(struct list_head *list)
258{
259 async_synchronize_cookie_domain(next_cookie, list);
260}
261EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
262
263/**
264 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
265 * @cookie: async_cookie_t to use as checkpoint
266 * @running: running list to synchronize on, NULL indicates all lists
267 *
268 * This function waits until all asynchronous function calls for the
269 * synchronization domain specified by the running list @list submitted
270 * prior to @cookie have been done.
271 */
272void async_synchronize_cookie_domain(async_cookie_t cookie,
273 struct list_head *running)
274{
275 ktime_t uninitialized_var(starttime), delta, endtime;
276
277 if (initcall_debug && system_state == SYSTEM_BOOTING) {
278 printk(KERN_DEBUG "async_waiting @ %i\n", task_pid_nr(current));
279 starttime = ktime_get();
280 }
281
282 wait_event(async_done, lowest_in_progress(running) >= cookie);
283
284 if (initcall_debug && system_state == SYSTEM_BOOTING) {
285 endtime = ktime_get();
286 delta = ktime_sub(endtime, starttime);
287
288 printk(KERN_DEBUG "async_continuing @ %i after %lli usec\n",
289 task_pid_nr(current),
290 (long long)ktime_to_ns(delta) >> 10);
291 }
292}
293EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
294
295/**
296 * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing
297 * @cookie: async_cookie_t to use as checkpoint
298 *
299 * This function waits until all asynchronous function calls prior to @cookie
300 * have been done.
301 */
302void async_synchronize_cookie(async_cookie_t cookie)
303{
304 async_synchronize_cookie_domain(cookie, &async_running);
305}
306EXPORT_SYMBOL_GPL(async_synchronize_cookie);