core/thread/schedule.c

   1 #include <klibc/compiler.h>
   2 #include <sys/cpu.h>
   3 #include "thread.h"
   4 #include "core.h"
   5 #include <dprintf.h>
   6
   7 void (*sched_hook_func)(void);
   8
   9 /*
  10  * __schedule() should only be called with interrupts locked out!
  11  */
  12 void __schedule(void)
  13 {
  14     static bool in_sched_hook;
  15     struct thread *curr = current();
  16     struct thread *st, *nt, *best;
  17
  18 #if DEBUG
  19     if (__unlikely(irq_state() & 0x200)) {
  20         dprintf("In __schedule with interrupts on!\n");
  21         kaboom();
  22     }
  23 #endif
  24
  25     /*
  26      * Are we called from inside sched_hook_func()?  If so we'll
  27      * schedule anyway on the way out.
  28      */
  29     if (in_sched_hook)
  30         return;
  31
  32     dprintf("Schedule ");
  33
  34     /* Possibly update the information on which we make
  35      * scheduling decisions.
  36      */
  37     if (sched_hook_func) {
  38         in_sched_hook = true;
  39         sched_hook_func();
  40         in_sched_hook = false;
  41     }
  42
  43     /*
  44      * The unusual form of this walk is because we have to start with
  45      * the thread *following* curr, and curr may not actually be part
  46      * of the list anymore (in the case of __exit_thread).
  47      */
  48     best = NULL;
  49     nt = st = container_of(curr->list.next, struct thread, list);
  50     do {
  51         if (__unlikely(nt->thread_magic != THREAD_MAGIC)) {
  52             dprintf("Invalid thread on thread list %p magic = 0x%08x\n",
  53                     nt, nt->thread_magic);
  54             kaboom();
  55         }
  56
  57         dprintf("Thread %p (%s) ", nt, nt->name);
  58         if (!nt->blocked) {
  59             dprintf("runnable priority %d\n", nt->prio);
  60             if (!best || nt->prio < best->prio)
  61                 best = nt;
  62         } else {
  63             dprintf("blocked\n");
  64         }
  65         nt = container_of(nt->list.next, struct thread, list);
  66     } while (nt != st);
  67
  68     if (!best)
  69         kaboom();               /* No runnable thread */
  70
  71     if (best != curr) {
  72         uint64_t tsc;
  73
  74         asm volatile("rdtsc" : "=A" (tsc));
  75
  76         dprintf("@ %llu -> %p (%s)\n", tsc, best, best->name);
  77         __switch_to(best);
  78     } else {
  79         dprintf("no change\n");
  80     }
  81 }
  82
  83 /*
  84  * This can be called from "normal" code...
  85  */
  86 void thread_yield(void)
  87 {
  88     irq_state_t irq = irq_save();
  89     __schedule();
  90     irq_restore(irq);
  91 }