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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