1 /*
2 * Virtual cpu timer based timer functions.
3 *
4 * Copyright IBM Corp. 2004, 2012
5 * Author(s): Jan Glauber <jan.glauber@de.ibm.com>
6 */
7
8 #include <linux/kernel_stat.h>
9 #include <linux/export.h>
10 #include <linux/kernel.h>
11 #include <linux/timex.h>
12 #include <linux/types.h>
13 #include <linux/time.h>
14
15 #include <asm/cputime.h>
16 #include <asm/vtimer.h>
17 #include <asm/vtime.h>
18
19 static void virt_timer_expire(void);
20
21 static LIST_HEAD(virt_timer_list);
22 static DEFINE_SPINLOCK(virt_timer_lock);
23 static atomic64_t virt_timer_current;
24 static atomic64_t virt_timer_elapsed;
25
get_vtimer(void)26 static inline u64 get_vtimer(void)
27 {
28 u64 timer;
29
30 asm volatile("stpt %0" : "=m" (timer));
31 return timer;
32 }
33
set_vtimer(u64 expires)34 static inline void set_vtimer(u64 expires)
35 {
36 u64 timer;
37
38 asm volatile(
39 " stpt %0\n" /* Store current cpu timer value */
40 " spt %1" /* Set new value imm. afterwards */
41 : "=m" (timer) : "m" (expires));
42 S390_lowcore.system_timer += S390_lowcore.last_update_timer - timer;
43 S390_lowcore.last_update_timer = expires;
44 }
45
virt_timer_forward(u64 elapsed)46 static inline int virt_timer_forward(u64 elapsed)
47 {
48 BUG_ON(!irqs_disabled());
49
50 if (list_empty(&virt_timer_list))
51 return 0;
52 elapsed = atomic64_add_return(elapsed, &virt_timer_elapsed);
53 return elapsed >= atomic64_read(&virt_timer_current);
54 }
55
56 /*
57 * Update process times based on virtual cpu times stored by entry.S
58 * to the lowcore fields user_timer, system_timer & steal_clock.
59 */
do_account_vtime(struct task_struct * tsk,int hardirq_offset)60 static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
61 {
62 struct thread_info *ti = task_thread_info(tsk);
63 u64 timer, clock, user, system, steal;
64
65 timer = S390_lowcore.last_update_timer;
66 clock = S390_lowcore.last_update_clock;
67 asm volatile(
68 " stpt %0\n" /* Store current cpu timer value */
69 #ifdef CONFIG_HAVE_MARCH_Z9_109_FEATURES
70 " stckf %1" /* Store current tod clock value */
71 #else
72 " stck %1" /* Store current tod clock value */
73 #endif
74 : "=m" (S390_lowcore.last_update_timer),
75 "=m" (S390_lowcore.last_update_clock));
76 S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
77 S390_lowcore.steal_timer += S390_lowcore.last_update_clock - clock;
78
79 user = S390_lowcore.user_timer - ti->user_timer;
80 S390_lowcore.steal_timer -= user;
81 ti->user_timer = S390_lowcore.user_timer;
82 account_user_time(tsk, user, user);
83
84 system = S390_lowcore.system_timer - ti->system_timer;
85 S390_lowcore.steal_timer -= system;
86 ti->system_timer = S390_lowcore.system_timer;
87 account_system_time(tsk, hardirq_offset, system, system);
88
89 steal = S390_lowcore.steal_timer;
90 if ((s64) steal > 0) {
91 S390_lowcore.steal_timer = 0;
92 account_steal_time(steal);
93 }
94
95 return virt_timer_forward(user + system);
96 }
97
vtime_task_switch(struct task_struct * prev)98 void vtime_task_switch(struct task_struct *prev)
99 {
100 struct thread_info *ti;
101
102 do_account_vtime(prev, 0);
103 ti = task_thread_info(prev);
104 ti->user_timer = S390_lowcore.user_timer;
105 ti->system_timer = S390_lowcore.system_timer;
106 ti = task_thread_info(current);
107 S390_lowcore.user_timer = ti->user_timer;
108 S390_lowcore.system_timer = ti->system_timer;
109 }
110
111 /*
112 * In s390, accounting pending user time also implies
113 * accounting system time in order to correctly compute
114 * the stolen time accounting.
115 */
vtime_account_user(struct task_struct * tsk)116 void vtime_account_user(struct task_struct *tsk)
117 {
118 if (do_account_vtime(tsk, HARDIRQ_OFFSET))
119 virt_timer_expire();
120 }
121
122 /*
123 * Update process times based on virtual cpu times stored by entry.S
124 * to the lowcore fields user_timer, system_timer & steal_clock.
125 */
vtime_account_irq_enter(struct task_struct * tsk)126 void vtime_account_irq_enter(struct task_struct *tsk)
127 {
128 struct thread_info *ti = task_thread_info(tsk);
129 u64 timer, system;
130
131 WARN_ON_ONCE(!irqs_disabled());
132
133 timer = S390_lowcore.last_update_timer;
134 S390_lowcore.last_update_timer = get_vtimer();
135 S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
136
137 system = S390_lowcore.system_timer - ti->system_timer;
138 S390_lowcore.steal_timer -= system;
139 ti->system_timer = S390_lowcore.system_timer;
140 account_system_time(tsk, 0, system, system);
141
142 virt_timer_forward(system);
143 }
144 EXPORT_SYMBOL_GPL(vtime_account_irq_enter);
145
146 void vtime_account_system(struct task_struct *tsk)
147 __attribute__((alias("vtime_account_irq_enter")));
148 EXPORT_SYMBOL_GPL(vtime_account_system);
149
150 /*
151 * Sorted add to a list. List is linear searched until first bigger
152 * element is found.
153 */
list_add_sorted(struct vtimer_list * timer,struct list_head * head)154 static void list_add_sorted(struct vtimer_list *timer, struct list_head *head)
155 {
156 struct vtimer_list *tmp;
157
158 list_for_each_entry(tmp, head, entry) {
159 if (tmp->expires > timer->expires) {
160 list_add_tail(&timer->entry, &tmp->entry);
161 return;
162 }
163 }
164 list_add_tail(&timer->entry, head);
165 }
166
167 /*
168 * Handler for expired virtual CPU timer.
169 */
virt_timer_expire(void)170 static void virt_timer_expire(void)
171 {
172 struct vtimer_list *timer, *tmp;
173 unsigned long elapsed;
174 LIST_HEAD(cb_list);
175
176 /* walk timer list, fire all expired timers */
177 spin_lock(&virt_timer_lock);
178 elapsed = atomic64_read(&virt_timer_elapsed);
179 list_for_each_entry_safe(timer, tmp, &virt_timer_list, entry) {
180 if (timer->expires < elapsed)
181 /* move expired timer to the callback queue */
182 list_move_tail(&timer->entry, &cb_list);
183 else
184 timer->expires -= elapsed;
185 }
186 if (!list_empty(&virt_timer_list)) {
187 timer = list_first_entry(&virt_timer_list,
188 struct vtimer_list, entry);
189 atomic64_set(&virt_timer_current, timer->expires);
190 }
191 atomic64_sub(elapsed, &virt_timer_elapsed);
192 spin_unlock(&virt_timer_lock);
193
194 /* Do callbacks and recharge periodic timers */
195 list_for_each_entry_safe(timer, tmp, &cb_list, entry) {
196 list_del_init(&timer->entry);
197 timer->function(timer->data);
198 if (timer->interval) {
199 /* Recharge interval timer */
200 timer->expires = timer->interval +
201 atomic64_read(&virt_timer_elapsed);
202 spin_lock(&virt_timer_lock);
203 list_add_sorted(timer, &virt_timer_list);
204 spin_unlock(&virt_timer_lock);
205 }
206 }
207 }
208
init_virt_timer(struct vtimer_list * timer)209 void init_virt_timer(struct vtimer_list *timer)
210 {
211 timer->function = NULL;
212 INIT_LIST_HEAD(&timer->entry);
213 }
214 EXPORT_SYMBOL(init_virt_timer);
215
vtimer_pending(struct vtimer_list * timer)216 static inline int vtimer_pending(struct vtimer_list *timer)
217 {
218 return !list_empty(&timer->entry);
219 }
220
internal_add_vtimer(struct vtimer_list * timer)221 static void internal_add_vtimer(struct vtimer_list *timer)
222 {
223 if (list_empty(&virt_timer_list)) {
224 /* First timer, just program it. */
225 atomic64_set(&virt_timer_current, timer->expires);
226 atomic64_set(&virt_timer_elapsed, 0);
227 list_add(&timer->entry, &virt_timer_list);
228 } else {
229 /* Update timer against current base. */
230 timer->expires += atomic64_read(&virt_timer_elapsed);
231 if (likely((s64) timer->expires <
232 (s64) atomic64_read(&virt_timer_current)))
233 /* The new timer expires before the current timer. */
234 atomic64_set(&virt_timer_current, timer->expires);
235 /* Insert new timer into the list. */
236 list_add_sorted(timer, &virt_timer_list);
237 }
238 }
239
__add_vtimer(struct vtimer_list * timer,int periodic)240 static void __add_vtimer(struct vtimer_list *timer, int periodic)
241 {
242 unsigned long flags;
243
244 timer->interval = periodic ? timer->expires : 0;
245 spin_lock_irqsave(&virt_timer_lock, flags);
246 internal_add_vtimer(timer);
247 spin_unlock_irqrestore(&virt_timer_lock, flags);
248 }
249
250 /*
251 * add_virt_timer - add an oneshot virtual CPU timer
252 */
add_virt_timer(struct vtimer_list * timer)253 void add_virt_timer(struct vtimer_list *timer)
254 {
255 __add_vtimer(timer, 0);
256 }
257 EXPORT_SYMBOL(add_virt_timer);
258
259 /*
260 * add_virt_timer_int - add an interval virtual CPU timer
261 */
add_virt_timer_periodic(struct vtimer_list * timer)262 void add_virt_timer_periodic(struct vtimer_list *timer)
263 {
264 __add_vtimer(timer, 1);
265 }
266 EXPORT_SYMBOL(add_virt_timer_periodic);
267
__mod_vtimer(struct vtimer_list * timer,u64 expires,int periodic)268 static int __mod_vtimer(struct vtimer_list *timer, u64 expires, int periodic)
269 {
270 unsigned long flags;
271 int rc;
272
273 BUG_ON(!timer->function);
274
275 if (timer->expires == expires && vtimer_pending(timer))
276 return 1;
277 spin_lock_irqsave(&virt_timer_lock, flags);
278 rc = vtimer_pending(timer);
279 if (rc)
280 list_del_init(&timer->entry);
281 timer->interval = periodic ? expires : 0;
282 timer->expires = expires;
283 internal_add_vtimer(timer);
284 spin_unlock_irqrestore(&virt_timer_lock, flags);
285 return rc;
286 }
287
288 /*
289 * returns whether it has modified a pending timer (1) or not (0)
290 */
mod_virt_timer(struct vtimer_list * timer,u64 expires)291 int mod_virt_timer(struct vtimer_list *timer, u64 expires)
292 {
293 return __mod_vtimer(timer, expires, 0);
294 }
295 EXPORT_SYMBOL(mod_virt_timer);
296
297 /*
298 * returns whether it has modified a pending timer (1) or not (0)
299 */
mod_virt_timer_periodic(struct vtimer_list * timer,u64 expires)300 int mod_virt_timer_periodic(struct vtimer_list *timer, u64 expires)
301 {
302 return __mod_vtimer(timer, expires, 1);
303 }
304 EXPORT_SYMBOL(mod_virt_timer_periodic);
305
306 /*
307 * Delete a virtual timer.
308 *
309 * returns whether the deleted timer was pending (1) or not (0)
310 */
del_virt_timer(struct vtimer_list * timer)311 int del_virt_timer(struct vtimer_list *timer)
312 {
313 unsigned long flags;
314
315 if (!vtimer_pending(timer))
316 return 0;
317 spin_lock_irqsave(&virt_timer_lock, flags);
318 list_del_init(&timer->entry);
319 spin_unlock_irqrestore(&virt_timer_lock, flags);
320 return 1;
321 }
322 EXPORT_SYMBOL(del_virt_timer);
323
324 /*
325 * Start the virtual CPU timer on the current CPU.
326 */
vtime_init(void)327 void vtime_init(void)
328 {
329 /* set initial cpu timer */
330 set_vtimer(VTIMER_MAX_SLICE);
331 }
332