arch/s390/kernel/vtime.c

   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/notifier.h>
  10 #include <linux/kprobes.h>
  11 #include <linux/export.h>
  12 #include <linux/kernel.h>
  13 #include <linux/timex.h>
  14 #include <linux/types.h>
  15 #include <linux/time.h>
  16 #include <linux/cpu.h>
  17 #include <linux/smp.h>
  18
  19 #include <asm/irq_regs.h>
  20 #include <asm/cputime.h>
  21 #include <asm/vtimer.h>
  22 #include <asm/vtime.h>
  23 #include <asm/irq.h>
  24 #include "entry.h"
  25
  26 static void virt_timer_expire(void);
  27
  28 DEFINE_PER_CPU(struct s390_idle_data, s390_idle);
  29
  30 static LIST_HEAD(virt_timer_list);
  31 static DEFINE_SPINLOCK(virt_timer_lock);
  32 static atomic64_t virt_timer_current;
  33 static atomic64_t virt_timer_elapsed;
  34
  35 static inline u64 get_vtimer(void)
  36 {
  37         u64 timer;
  38
  39         asm volatile("stpt %0" : "=m" (timer));
  40         return timer;
  41 }
  42
  43 static inline void set_vtimer(u64 expires)
  44 {
  45         u64 timer;
  46
  47         asm volatile(
  48                 "       stpt    %0\n"   /* Store current cpu timer value */
  49                 "       spt     %1"     /* Set new value imm. afterwards */
  50                 : "=m" (timer) : "m" (expires));
  51         S390_lowcore.system_timer += S390_lowcore.last_update_timer - timer;
  52         S390_lowcore.last_update_timer = expires;
  53 }
  54
  55 static inline int virt_timer_forward(u64 elapsed)
  56 {
  57         BUG_ON(!irqs_disabled());
  58
  59         if (list_empty(&virt_timer_list))
  60                 return 0;
  61         elapsed = atomic64_add_return(elapsed, &virt_timer_elapsed);
  62         return elapsed >= atomic64_read(&virt_timer_current);
  63 }
  64
  65 /*
  66  * Update process times based on virtual cpu times stored by entry.S
  67  * to the lowcore fields user_timer, system_timer & steal_clock.
  68  */
  69 static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
  70 {
  71         struct thread_info *ti = task_thread_info(tsk);
  72         u64 timer, clock, user, system, steal;
  73
  74         timer = S390_lowcore.last_update_timer;
  75         clock = S390_lowcore.last_update_clock;
  76         asm volatile(
  77                 "       stpt    %0\n"   /* Store current cpu timer value */
  78                 "       stck    %1"     /* Store current tod clock value */
  79                 : "=m" (S390_lowcore.last_update_timer),
  80                   "=m" (S390_lowcore.last_update_clock));
  81         S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
  82         S390_lowcore.steal_timer += S390_lowcore.last_update_clock - clock;
  83
  84         user = S390_lowcore.user_timer - ti->user_timer;
  85         S390_lowcore.steal_timer -= user;
  86         ti->user_timer = S390_lowcore.user_timer;
  87         account_user_time(tsk, user, user);
  88
  89         system = S390_lowcore.system_timer - ti->system_timer;
  90         S390_lowcore.steal_timer -= system;
  91         ti->system_timer = S390_lowcore.system_timer;
  92         account_system_time(tsk, hardirq_offset, system, system);
  93
  94         steal = S390_lowcore.steal_timer;
  95         if ((s64) steal > 0) {
  96                 S390_lowcore.steal_timer = 0;
  97                 account_steal_time(steal);
  98         }
  99
 100         return virt_timer_forward(user + system);
 101 }
 102
 103 void vtime_task_switch(struct task_struct *prev)
 104 {
 105         struct thread_info *ti;
 106
 107         do_account_vtime(prev, 0);
 108         ti = task_thread_info(prev);
 109         ti->user_timer = S390_lowcore.user_timer;
 110         ti->system_timer = S390_lowcore.system_timer;
 111         ti = task_thread_info(current);
 112         S390_lowcore.user_timer = ti->user_timer;
 113         S390_lowcore.system_timer = ti->system_timer;
 114 }
 115
 116 /*
 117  * In s390, accounting pending user time also implies
 118  * accounting system time in order to correctly compute
 119  * the stolen time accounting.
 120  */
 121 void vtime_account_user(struct task_struct *tsk)
 122 {
 123         if (do_account_vtime(tsk, HARDIRQ_OFFSET))
 124                 virt_timer_expire();
 125 }
 126
 127 /*
 128  * Update process times based on virtual cpu times stored by entry.S
 129  * to the lowcore fields user_timer, system_timer & steal_clock.
 130  */
 131 void vtime_account_irq_enter(struct task_struct *tsk)
 132 {
 133         struct thread_info *ti = task_thread_info(tsk);
 134         u64 timer, system;
 135
 136         WARN_ON_ONCE(!irqs_disabled());
 137
 138         timer = S390_lowcore.last_update_timer;
 139         S390_lowcore.last_update_timer = get_vtimer();
 140         S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
 141
 142         system = S390_lowcore.system_timer - ti->system_timer;
 143         S390_lowcore.steal_timer -= system;
 144         ti->system_timer = S390_lowcore.system_timer;
 145         account_system_time(tsk, 0, system, system);
 146
 147         virt_timer_forward(system);
 148 }
 149 EXPORT_SYMBOL_GPL(vtime_account_irq_enter);
 150
 151 void vtime_account_system(struct task_struct *tsk)
 152 __attribute__((alias("vtime_account_irq_enter")));
 153 EXPORT_SYMBOL_GPL(vtime_account_system);
 154
 155 void __kprobes vtime_stop_cpu(void)
 156 {
 157         struct s390_idle_data *idle = &__get_cpu_var(s390_idle);
 158         unsigned long long idle_time;
 159         unsigned long psw_mask;
 160
 161         trace_hardirqs_on();
 162
 163         /* Wait for external, I/O or machine check interrupt. */
 164         psw_mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_DAT |
 165                 PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
 166         idle->nohz_delay = 0;
 167
 168         /* Call the assembler magic in entry.S */
 169         psw_idle(idle, psw_mask);
 170
 171         /* Account time spent with enabled wait psw loaded as idle time. */
 172         idle->sequence++;
 173         smp_wmb();
 174         idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
 175         idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
 176         idle->idle_time += idle_time;
 177         idle->idle_count++;
 178         account_idle_time(idle_time);
 179         smp_wmb();
 180         idle->sequence++;
 181 }
 182
 183 cputime64_t s390_get_idle_time(int cpu)
 184 {
 185         struct s390_idle_data *idle = &per_cpu(s390_idle, cpu);
 186         unsigned long long now, idle_enter, idle_exit;
 187         unsigned int sequence;
 188
 189         do {
 190                 now = get_tod_clock();
 191                 sequence = ACCESS_ONCE(idle->sequence);
 192                 idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
 193                 idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
 194         } while ((sequence & 1) || (ACCESS_ONCE(idle->sequence) != sequence));
 195         return idle_enter ? ((idle_exit ?: now) - idle_enter) : 0;
 196 }
 197
 198 /*
 199  * Sorted add to a list. List is linear searched until first bigger
 200  * element is found.
 201  */
 202 static void list_add_sorted(struct vtimer_list *timer, struct list_head *head)
 203 {
 204         struct vtimer_list *tmp;
 205
 206         list_for_each_entry(tmp, head, entry) {
 207                 if (tmp->expires > timer->expires) {
 208                         list_add_tail(&timer->entry, &tmp->entry);
 209                         return;
 210                 }
 211         }
 212         list_add_tail(&timer->entry, head);
 213 }
 214
 215 /*
 216  * Handler for expired virtual CPU timer.
 217  */
 218 static void virt_timer_expire(void)
 219 {
 220         struct vtimer_list *timer, *tmp;
 221         unsigned long elapsed;
 222         LIST_HEAD(cb_list);
 223
 224         /* walk timer list, fire all expired timers */
 225         spin_lock(&virt_timer_lock);
 226         elapsed = atomic64_read(&virt_timer_elapsed);
 227         list_for_each_entry_safe(timer, tmp, &virt_timer_list, entry) {
 228                 if (timer->expires < elapsed)
 229                         /* move expired timer to the callback queue */
 230                         list_move_tail(&timer->entry, &cb_list);
 231                 else
 232                         timer->expires -= elapsed;
 233         }
 234         if (!list_empty(&virt_timer_list)) {
 235                 timer = list_first_entry(&virt_timer_list,
 236                                          struct vtimer_list, entry);
 237                 atomic64_set(&virt_timer_current, timer->expires);
 238         }
 239         atomic64_sub(elapsed, &virt_timer_elapsed);
 240         spin_unlock(&virt_timer_lock);
 241
 242         /* Do callbacks and recharge periodic timers */
 243         list_for_each_entry_safe(timer, tmp, &cb_list, entry) {
 244                 list_del_init(&timer->entry);
 245                 timer->function(timer->data);
 246                 if (timer->interval) {
 247                         /* Recharge interval timer */
 248                         timer->expires = timer->interval +
 249                                 atomic64_read(&virt_timer_elapsed);
 250                         spin_lock(&virt_timer_lock);
 251                         list_add_sorted(timer, &virt_timer_list);
 252                         spin_unlock(&virt_timer_lock);
 253                 }
 254         }
 255 }
 256
 257 void init_virt_timer(struct vtimer_list *timer)
 258 {
 259         timer->function = NULL;
 260         INIT_LIST_HEAD(&timer->entry);
 261 }
 262 EXPORT_SYMBOL(init_virt_timer);
 263
 264 static inline int vtimer_pending(struct vtimer_list *timer)
 265 {
 266         return !list_empty(&timer->entry);
 267 }
 268
 269 static void internal_add_vtimer(struct vtimer_list *timer)
 270 {
 271         if (list_empty(&virt_timer_list)) {
 272                 /* First timer, just program it. */
 273                 atomic64_set(&virt_timer_current, timer->expires);
 274                 atomic64_set(&virt_timer_elapsed, 0);
 275                 list_add(&timer->entry, &virt_timer_list);
 276         } else {
 277                 /* Update timer against current base. */
 278                 timer->expires += atomic64_read(&virt_timer_elapsed);
 279                 if (likely((s64) timer->expires <
 280                            (s64) atomic64_read(&virt_timer_current)))
 281                         /* The new timer expires before the current timer. */
 282                         atomic64_set(&virt_timer_current, timer->expires);
 283                 /* Insert new timer into the list. */
 284                 list_add_sorted(timer, &virt_timer_list);
 285         }
 286 }
 287
 288 static void __add_vtimer(struct vtimer_list *timer, int periodic)
 289 {
 290         unsigned long flags;
 291
 292         timer->interval = periodic ? timer->expires : 0;
 293         spin_lock_irqsave(&virt_timer_lock, flags);
 294         internal_add_vtimer(timer);
 295         spin_unlock_irqrestore(&virt_timer_lock, flags);
 296 }
 297
 298 /*
 299  * add_virt_timer - add an oneshot virtual CPU timer
 300  */
 301 void add_virt_timer(struct vtimer_list *timer)
 302 {
 303         __add_vtimer(timer, 0);
 304 }
 305 EXPORT_SYMBOL(add_virt_timer);
 306
 307 /*
 308  * add_virt_timer_int - add an interval virtual CPU timer
 309  */
 310 void add_virt_timer_periodic(struct vtimer_list *timer)
 311 {
 312         __add_vtimer(timer, 1);
 313 }
 314 EXPORT_SYMBOL(add_virt_timer_periodic);
 315
 316 static int __mod_vtimer(struct vtimer_list *timer, u64 expires, int periodic)
 317 {
 318         unsigned long flags;
 319         int rc;
 320
 321         BUG_ON(!timer->function);
 322
 323         if (timer->expires == expires && vtimer_pending(timer))
 324                 return 1;
 325         spin_lock_irqsave(&virt_timer_lock, flags);
 326         rc = vtimer_pending(timer);
 327         if (rc)
 328                 list_del_init(&timer->entry);
 329         timer->interval = periodic ? expires : 0;
 330         timer->expires = expires;
 331         internal_add_vtimer(timer);
 332         spin_unlock_irqrestore(&virt_timer_lock, flags);
 333         return rc;
 334 }
 335
 336 /*
 337  * returns whether it has modified a pending timer (1) or not (0)
 338  */
 339 int mod_virt_timer(struct vtimer_list *timer, u64 expires)
 340 {
 341         return __mod_vtimer(timer, expires, 0);
 342 }
 343 EXPORT_SYMBOL(mod_virt_timer);
 344
 345 /*
 346  * returns whether it has modified a pending timer (1) or not (0)
 347  */
 348 int mod_virt_timer_periodic(struct vtimer_list *timer, u64 expires)
 349 {
 350         return __mod_vtimer(timer, expires, 1);
 351 }
 352 EXPORT_SYMBOL(mod_virt_timer_periodic);
 353
 354 /*
 355  * Delete a virtual timer.
 356  *
 357  * returns whether the deleted timer was pending (1) or not (0)
 358  */
 359 int del_virt_timer(struct vtimer_list *timer)
 360 {
 361         unsigned long flags;
 362
 363         if (!vtimer_pending(timer))
 364                 return 0;
 365         spin_lock_irqsave(&virt_timer_lock, flags);
 366         list_del_init(&timer->entry);
 367         spin_unlock_irqrestore(&virt_timer_lock, flags);
 368         return 1;
 369 }
 370 EXPORT_SYMBOL(del_virt_timer);
 371
 372 /*
 373  * Start the virtual CPU timer on the current CPU.
 374  */
 375 void init_cpu_vtimer(void)
 376 {
 377         /* set initial cpu timer */
 378         set_vtimer(VTIMER_MAX_SLICE);
 379 }
 380
 381 static int s390_nohz_notify(struct notifier_block *self, unsigned long action,
 382                             void *hcpu)
 383 {
 384         struct s390_idle_data *idle;
 385         long cpu = (long) hcpu;
 386
 387         idle = &per_cpu(s390_idle, cpu);
 388         switch (action & ~CPU_TASKS_FROZEN) {
 389         case CPU_DYING:
 390                 idle->nohz_delay = 0;
 391         default:
 392                 break;
 393         }
 394         return NOTIFY_OK;
 395 }
 396
 397 void __init vtime_init(void)
 398 {
 399         /* Enable cpu timer interrupts on the boot cpu. */
 400         init_cpu_vtimer();
 401         cpu_notifier(s390_nohz_notify, 0);
 402 }