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b886d83c | 1 | // SPDX-License-Identifier: GPL-2.0-only |
22a9d645 AV |
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> | |
22a9d645 AV |
7 | */ |
8 | ||
9 | ||
10 | /* | |
11 | ||
12 | Goals and Theory of Operation | |
13 | ||
14 | The primary goal of this feature is to reduce the kernel boot time, | |
15 | by doing various independent hardware delays and discovery operations | |
16 | decoupled and not strictly serialized. | |
17 | ||
18 | More specifically, the asynchronous function call concept allows | |
19 | certain operations (primarily during system boot) to happen | |
20 | asynchronously, out of order, while these operations still | |
21 | have their externally visible parts happen sequentially and in-order. | |
22 | (not unlike how out-of-order CPUs retire their instructions in order) | |
23 | ||
24 | Key to the asynchronous function call implementation is the concept of | |
25 | a "sequence cookie" (which, although it has an abstracted type, can be | |
26 | thought of as a monotonically incrementing number). | |
27 | ||
28 | The async core will assign each scheduled event such a sequence cookie and | |
29 | pass this to the called functions. | |
30 | ||
31 | The asynchronously called function should before doing a globally visible | |
32 | operation, such as registering device numbers, call the | |
33 | async_synchronize_cookie() function and pass in its own cookie. The | |
34 | async_synchronize_cookie() function will make sure that all asynchronous | |
35 | operations that were scheduled prior to the operation corresponding with the | |
36 | cookie have completed. | |
37 | ||
38 | Subsystem/driver initialization code that scheduled asynchronous probe | |
39 | functions, but which shares global resources with other drivers/subsystems | |
40 | that do not use the asynchronous call feature, need to do a full | |
41 | synchronization with the async_synchronize_full() function, before returning | |
42 | from their init function. This is to maintain strict ordering between the | |
43 | asynchronous and synchronous parts of the kernel. | |
44 | ||
45 | */ | |
46 | ||
47 | #include <linux/async.h> | |
84c15027 | 48 | #include <linux/atomic.h> |
9984de1a | 49 | #include <linux/export.h> |
f551103c KO |
50 | #include <linux/ktime.h> |
51 | #include <linux/pid.h> | |
22a9d645 | 52 | #include <linux/sched.h> |
5a0e3ad6 | 53 | #include <linux/slab.h> |
f551103c | 54 | #include <linux/wait.h> |
083b804c | 55 | #include <linux/workqueue.h> |
22a9d645 | 56 | |
84b233ad TH |
57 | #include "workqueue_internal.h" |
58 | ||
22a9d645 AV |
59 | static async_cookie_t next_cookie = 1; |
60 | ||
c68eee14 TH |
61 | #define MAX_WORK 32768 |
62 | #define ASYNC_COOKIE_MAX ULLONG_MAX /* infinity cookie */ | |
22a9d645 | 63 | |
9fdb04cd | 64 | static LIST_HEAD(async_global_pending); /* pending from all registered doms */ |
8723d503 | 65 | static ASYNC_DOMAIN(async_dfl_domain); |
22a9d645 AV |
66 | static DEFINE_SPINLOCK(async_lock); |
67 | ||
68 | struct async_entry { | |
9fdb04cd TH |
69 | struct list_head domain_list; |
70 | struct list_head global_list; | |
083b804c TH |
71 | struct work_struct work; |
72 | async_cookie_t cookie; | |
362f2b09 | 73 | async_func_t func; |
083b804c | 74 | void *data; |
8723d503 | 75 | struct async_domain *domain; |
22a9d645 AV |
76 | }; |
77 | ||
78 | static DECLARE_WAIT_QUEUE_HEAD(async_done); | |
22a9d645 AV |
79 | |
80 | static atomic_t entry_count; | |
22a9d645 | 81 | |
07416af1 RV |
82 | static 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 | ||
8723d503 | 88 | static async_cookie_t lowest_in_progress(struct async_domain *domain) |
37a76bd4 | 89 | { |
4f7e988e | 90 | struct async_entry *first = NULL; |
52722794 | 91 | async_cookie_t ret = ASYNC_COOKIE_MAX; |
37a76bd4 | 92 | unsigned long flags; |
37a76bd4 AV |
93 | |
94 | spin_lock_irqsave(&async_lock, flags); | |
9fdb04cd | 95 | |
4f7e988e RV |
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 | } | |
9fdb04cd | 105 | |
4f7e988e RV |
106 | if (first) |
107 | ret = first->cookie; | |
9fdb04cd | 108 | |
37a76bd4 AV |
109 | spin_unlock_irqrestore(&async_lock, flags); |
110 | return ret; | |
111 | } | |
083b804c | 112 | |
22a9d645 AV |
113 | /* |
114 | * pick the first pending entry and run it | |
115 | */ | |
083b804c | 116 | static void async_run_entry_fn(struct work_struct *work) |
22a9d645 | 117 | { |
083b804c TH |
118 | struct async_entry *entry = |
119 | container_of(work, struct async_entry, work); | |
22a9d645 | 120 | unsigned long flags; |
07416af1 | 121 | ktime_t calltime; |
22a9d645 | 122 | |
52722794 | 123 | /* 1) run (and print duration) */ |
07416af1 RV |
124 | pr_debug("calling %lli_%pS @ %i\n", (long long)entry->cookie, |
125 | entry->func, task_pid_nr(current)); | |
126 | calltime = ktime_get(); | |
127 | ||
22a9d645 | 128 | entry->func(entry->data, entry->cookie); |
07416af1 RV |
129 | |
130 | pr_debug("initcall %lli_%pS returned after %lld usecs\n", | |
131 | (long long)entry->cookie, entry->func, | |
132 | microseconds_since(calltime)); | |
22a9d645 | 133 | |
52722794 | 134 | /* 2) remove self from the pending queues */ |
22a9d645 | 135 | spin_lock_irqsave(&async_lock, flags); |
9fdb04cd TH |
136 | list_del_init(&entry->domain_list); |
137 | list_del_init(&entry->global_list); | |
22a9d645 | 138 | |
52722794 | 139 | /* 3) free the entry */ |
22a9d645 AV |
140 | kfree(entry); |
141 | atomic_dec(&entry_count); | |
142 | ||
143 | spin_unlock_irqrestore(&async_lock, flags); | |
144 | ||
52722794 | 145 | /* 4) wake up any waiters */ |
22a9d645 | 146 | wake_up(&async_done); |
22a9d645 AV |
147 | } |
148 | ||
6be9238e AD |
149 | /** |
150 | * async_schedule_node_domain - NUMA specific version of async_schedule_domain | |
151 | * @func: function to execute asynchronously | |
152 | * @data: data pointer to pass to the function | |
153 | * @node: NUMA node that we want to schedule this on or close to | |
154 | * @domain: the domain | |
155 | * | |
156 | * Returns an async_cookie_t that may be used for checkpointing later. | |
157 | * @domain may be used in the async_synchronize_*_domain() functions to | |
158 | * wait within a certain synchronization domain rather than globally. | |
159 | * | |
160 | * Note: This function may be called from atomic or non-atomic contexts. | |
161 | * | |
162 | * The node requested will be honored on a best effort basis. If the node | |
163 | * has no CPUs associated with it then the work is distributed among all | |
164 | * available CPUs. | |
165 | */ | |
166 | async_cookie_t async_schedule_node_domain(async_func_t func, void *data, | |
167 | int node, struct async_domain *domain) | |
22a9d645 AV |
168 | { |
169 | struct async_entry *entry; | |
170 | unsigned long flags; | |
171 | async_cookie_t newcookie; | |
22a9d645 AV |
172 | |
173 | /* allow irq-off callers */ | |
174 | entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC); | |
175 | ||
176 | /* | |
177 | * If we're out of memory or if there's too much work | |
178 | * pending already, we execute synchronously. | |
179 | */ | |
083b804c | 180 | if (!entry || atomic_read(&entry_count) > MAX_WORK) { |
22a9d645 AV |
181 | kfree(entry); |
182 | spin_lock_irqsave(&async_lock, flags); | |
183 | newcookie = next_cookie++; | |
184 | spin_unlock_irqrestore(&async_lock, flags); | |
185 | ||
186 | /* low on memory.. run synchronously */ | |
362f2b09 | 187 | func(data, newcookie); |
22a9d645 AV |
188 | return newcookie; |
189 | } | |
a0327ff0 JH |
190 | INIT_LIST_HEAD(&entry->domain_list); |
191 | INIT_LIST_HEAD(&entry->global_list); | |
083b804c | 192 | INIT_WORK(&entry->work, async_run_entry_fn); |
362f2b09 | 193 | entry->func = func; |
22a9d645 | 194 | entry->data = data; |
8723d503 | 195 | entry->domain = domain; |
22a9d645 AV |
196 | |
197 | spin_lock_irqsave(&async_lock, flags); | |
9fdb04cd TH |
198 | |
199 | /* allocate cookie and queue */ | |
22a9d645 | 200 | newcookie = entry->cookie = next_cookie++; |
9fdb04cd TH |
201 | |
202 | list_add_tail(&entry->domain_list, &domain->pending); | |
203 | if (domain->registered) | |
204 | list_add_tail(&entry->global_list, &async_global_pending); | |
205 | ||
22a9d645 AV |
206 | atomic_inc(&entry_count); |
207 | spin_unlock_irqrestore(&async_lock, flags); | |
083b804c TH |
208 | |
209 | /* schedule for execution */ | |
6be9238e | 210 | queue_work_node(node, system_unbound_wq, &entry->work); |
083b804c | 211 | |
22a9d645 AV |
212 | return newcookie; |
213 | } | |
6be9238e | 214 | EXPORT_SYMBOL_GPL(async_schedule_node_domain); |
22a9d645 | 215 | |
f30d5b30 | 216 | /** |
6be9238e | 217 | * async_schedule_node - NUMA specific version of async_schedule |
362f2b09 | 218 | * @func: function to execute asynchronously |
f30d5b30 | 219 | * @data: data pointer to pass to the function |
6be9238e | 220 | * @node: NUMA node that we want to schedule this on or close to |
f30d5b30 CH |
221 | * |
222 | * Returns an async_cookie_t that may be used for checkpointing later. | |
223 | * Note: This function may be called from atomic or non-atomic contexts. | |
f30d5b30 | 224 | * |
6be9238e AD |
225 | * The node requested will be honored on a best effort basis. If the node |
226 | * has no CPUs associated with it then the work is distributed among all | |
227 | * available CPUs. | |
f30d5b30 | 228 | */ |
6be9238e | 229 | async_cookie_t async_schedule_node(async_func_t func, void *data, int node) |
22a9d645 | 230 | { |
6be9238e | 231 | return async_schedule_node_domain(func, data, node, &async_dfl_domain); |
22a9d645 | 232 | } |
6be9238e | 233 | EXPORT_SYMBOL_GPL(async_schedule_node); |
22a9d645 | 234 | |
f30d5b30 CH |
235 | /** |
236 | * async_synchronize_full - synchronize all asynchronous function calls | |
237 | * | |
238 | * This function waits until all asynchronous function calls have been done. | |
239 | */ | |
22a9d645 AV |
240 | void async_synchronize_full(void) |
241 | { | |
9fdb04cd | 242 | async_synchronize_full_domain(NULL); |
22a9d645 AV |
243 | } |
244 | EXPORT_SYMBOL_GPL(async_synchronize_full); | |
245 | ||
f30d5b30 | 246 | /** |
766ccb9e | 247 | * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain |
8723d503 | 248 | * @domain: the domain to synchronize |
f30d5b30 | 249 | * |
766ccb9e | 250 | * This function waits until all asynchronous function calls for the |
8723d503 | 251 | * synchronization domain specified by @domain have been done. |
f30d5b30 | 252 | */ |
2955b47d | 253 | void async_synchronize_full_domain(struct async_domain *domain) |
22a9d645 | 254 | { |
c68eee14 | 255 | async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain); |
22a9d645 | 256 | } |
766ccb9e | 257 | EXPORT_SYMBOL_GPL(async_synchronize_full_domain); |
22a9d645 | 258 | |
f30d5b30 | 259 | /** |
766ccb9e | 260 | * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing |
f30d5b30 | 261 | * @cookie: async_cookie_t to use as checkpoint |
9fdb04cd | 262 | * @domain: the domain to synchronize (%NULL for all registered domains) |
f30d5b30 | 263 | * |
766ccb9e | 264 | * This function waits until all asynchronous function calls for the |
8723d503 TH |
265 | * synchronization domain specified by @domain submitted prior to @cookie |
266 | * have been done. | |
f30d5b30 | 267 | */ |
8723d503 | 268 | void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain) |
22a9d645 | 269 | { |
07416af1 | 270 | ktime_t starttime; |
22a9d645 | 271 | |
07416af1 RV |
272 | pr_debug("async_waiting @ %i\n", task_pid_nr(current)); |
273 | starttime = ktime_get(); | |
22a9d645 | 274 | |
8723d503 | 275 | wait_event(async_done, lowest_in_progress(domain) >= cookie); |
22a9d645 | 276 | |
07416af1 RV |
277 | pr_debug("async_continuing @ %i after %lli usec\n", task_pid_nr(current), |
278 | microseconds_since(starttime)); | |
22a9d645 | 279 | } |
766ccb9e | 280 | EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain); |
22a9d645 | 281 | |
f30d5b30 CH |
282 | /** |
283 | * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing | |
284 | * @cookie: async_cookie_t to use as checkpoint | |
285 | * | |
286 | * This function waits until all asynchronous function calls prior to @cookie | |
287 | * have been done. | |
288 | */ | |
22a9d645 AV |
289 | void async_synchronize_cookie(async_cookie_t cookie) |
290 | { | |
8723d503 | 291 | async_synchronize_cookie_domain(cookie, &async_dfl_domain); |
22a9d645 AV |
292 | } |
293 | EXPORT_SYMBOL_GPL(async_synchronize_cookie); | |
84b233ad TH |
294 | |
295 | /** | |
296 | * current_is_async - is %current an async worker task? | |
297 | * | |
298 | * Returns %true if %current is an async worker task. | |
299 | */ | |
300 | bool current_is_async(void) | |
301 | { | |
302 | struct worker *worker = current_wq_worker(); | |
303 | ||
304 | return worker && worker->current_func == async_run_entry_fn; | |
305 | } | |
581da2ca | 306 | EXPORT_SYMBOL_GPL(current_is_async); |