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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
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);
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/module.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
81extern int initcall_debug;
82
83
84/*
85 * MUST be called with the lock held!
86 */
87static async_cookie_t __lowest_in_progress(struct list_head *running)
88{
89 struct async_entry *entry;
90
91 if (!list_empty(running)) {
92 entry = list_first_entry(running,
93 struct async_entry, list);
94 return entry->cookie;
95 }
96
97 list_for_each_entry(entry, &async_pending, list)
98 if (entry->running == running)
99 return entry->cookie;
100
101 return next_cookie; /* "infinity" value */
102}
103
104static async_cookie_t lowest_in_progress(struct list_head *running)
105{
106 unsigned long flags;
107 async_cookie_t ret;
108
109 spin_lock_irqsave(&async_lock, flags);
110 ret = __lowest_in_progress(running);
111 spin_unlock_irqrestore(&async_lock, flags);
112 return ret;
113}
114
115/*
116 * pick the first pending entry and run it
117 */
118static void async_run_entry_fn(struct work_struct *work)
119{
120 struct async_entry *entry =
121 container_of(work, struct async_entry, work);
122 unsigned long flags;
123 ktime_t calltime, delta, rettime;
124
125 /* 1) move self to the running queue */
126 spin_lock_irqsave(&async_lock, flags);
127 list_move_tail(&entry->list, entry->running);
128 spin_unlock_irqrestore(&async_lock, flags);
129
130 /* 2) run (and print duration) */
131 if (initcall_debug && system_state == SYSTEM_BOOTING) {
132 printk(KERN_DEBUG "calling %lli_%pF @ %i\n",
133 (long long)entry->cookie,
134 entry->func, task_pid_nr(current));
135 calltime = ktime_get();
136 }
137 entry->func(entry->data, entry->cookie);
138 if (initcall_debug && system_state == SYSTEM_BOOTING) {
139 rettime = ktime_get();
140 delta = ktime_sub(rettime, calltime);
141 printk(KERN_DEBUG "initcall %lli_%pF returned 0 after %lld usecs\n",
142 (long long)entry->cookie,
143 entry->func,
144 (long long)ktime_to_ns(delta) >> 10);
145 }
146
147 /* 3) remove self from the running queue */
148 spin_lock_irqsave(&async_lock, flags);
149 list_del(&entry->list);
150
151 /* 4) free the entry */
152 kfree(entry);
153 atomic_dec(&entry_count);
154
155 spin_unlock_irqrestore(&async_lock, flags);
156
157 /* 5) wake up any waiters */
158 wake_up(&async_done);
159}
160
161static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct list_head *running)
162{
163 struct async_entry *entry;
164 unsigned long flags;
165 async_cookie_t newcookie;
166
167 /* allow irq-off callers */
168 entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
169
170 /*
171 * If we're out of memory or if there's too much work
172 * pending already, we execute synchronously.
173 */
174 if (!entry || atomic_read(&entry_count) > MAX_WORK) {
175 kfree(entry);
176 spin_lock_irqsave(&async_lock, flags);
177 newcookie = next_cookie++;
178 spin_unlock_irqrestore(&async_lock, flags);
179
180 /* low on memory.. run synchronously */
181 ptr(data, newcookie);
182 return newcookie;
183 }
184 INIT_WORK(&entry->work, async_run_entry_fn);
185 entry->func = ptr;
186 entry->data = data;
187 entry->running = running;
188
189 spin_lock_irqsave(&async_lock, flags);
190 newcookie = entry->cookie = next_cookie++;
191 list_add_tail(&entry->list, &async_pending);
192 atomic_inc(&entry_count);
193 spin_unlock_irqrestore(&async_lock, flags);
194
195 /* schedule for execution */
196 queue_work(system_unbound_wq, &entry->work);
197
198 return newcookie;
199}
200
201/**
202 * async_schedule - schedule a function for asynchronous execution
203 * @ptr: function to execute asynchronously
204 * @data: data pointer to pass to the function
205 *
206 * Returns an async_cookie_t that may be used for checkpointing later.
207 * Note: This function may be called from atomic or non-atomic contexts.
208 */
209async_cookie_t async_schedule(async_func_ptr *ptr, void *data)
210{
211 return __async_schedule(ptr, data, &async_running);
212}
213EXPORT_SYMBOL_GPL(async_schedule);
214
215/**
216 * async_schedule_domain - schedule a function for asynchronous execution within a certain domain
217 * @ptr: function to execute asynchronously
218 * @data: data pointer to pass to the function
219 * @running: running list for the domain
220 *
221 * Returns an async_cookie_t that may be used for checkpointing later.
222 * @running may be used in the async_synchronize_*_domain() functions
223 * to wait within a certain synchronization domain rather than globally.
224 * A synchronization domain is specified via the running queue @running to use.
225 * Note: This function may be called from atomic or non-atomic contexts.
226 */
227async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data,
228 struct list_head *running)
229{
230 return __async_schedule(ptr, data, running);
231}
232EXPORT_SYMBOL_GPL(async_schedule_domain);
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 do {
242 async_synchronize_cookie(next_cookie);
243 } while (!list_empty(&async_running) || !list_empty(&async_pending));
244}
245EXPORT_SYMBOL_GPL(async_synchronize_full);
246
247/**
248 * async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
249 * @list: running list to synchronize on
250 *
251 * This function waits until all asynchronous function calls for the
252 * synchronization domain specified by the running list @list have been done.
253 */
254void async_synchronize_full_domain(struct list_head *list)
255{
256 async_synchronize_cookie_domain(next_cookie, list);
257}
258EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
259
260/**
261 * async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
262 * @cookie: async_cookie_t to use as checkpoint
263 * @running: running list to synchronize on
264 *
265 * This function waits until all asynchronous function calls for the
266 * synchronization domain specified by the running list @list submitted
267 * prior to @cookie have been done.
268 */
269void async_synchronize_cookie_domain(async_cookie_t cookie,
270 struct list_head *running)
271{
272 ktime_t starttime, delta, endtime;
273
274 if (initcall_debug && system_state == SYSTEM_BOOTING) {
275 printk(KERN_DEBUG "async_waiting @ %i\n", task_pid_nr(current));
276 starttime = ktime_get();
277 }
278
279 wait_event(async_done, lowest_in_progress(running) >= cookie);
280
281 if (initcall_debug && system_state == SYSTEM_BOOTING) {
282 endtime = ktime_get();
283 delta = ktime_sub(endtime, starttime);
284
285 printk(KERN_DEBUG "async_continuing @ %i after %lli usec\n",
286 task_pid_nr(current),
287 (long long)ktime_to_ns(delta) >> 10);
288 }
289}
290EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
291
292/**
293 * async_synchronize_cookie - synchronize asynchronous function calls with cookie checkpointing
294 * @cookie: async_cookie_t to use as checkpoint
295 *
296 * This function waits until all asynchronous function calls prior to @cookie
297 * have been done.
298 */
299void async_synchronize_cookie(async_cookie_t cookie)
300{
301 async_synchronize_cookie_domain(cookie, &async_running);
302}
303EXPORT_SYMBOL_GPL(async_synchronize_cookie);