kernel/critical.c

   1 #include "critical.h"
   2 #include "general.h"
   3
   4 static volatile uint32_t spinlock = 0;     /* volatile to not optimize the smp_lock loop away */
   5
   6 void critical_enter(void)
   7 {
   8         cli();
   9 }
  10
  11 void critical_exit(void)
  12 {
  13         sti();
  14 }
  15
  16 /* mb = memory barrier, used for code synchronization */
  17 void memory_barrier(void)
  18 {
  19         asm volatile("mfence");
  20 }
  21
  22 void smp_lock(void)
  23 {
  24     critical_enter();   /* disable interrupt */
  25     memory_barrier();               /* syncronize */
  26     asm volatile(
  27         "lock_loop:                 "
  28         "    pause;                 " /* used to optimize loops on P4/Xeon's */
  29         "    lock btsl $0x00, %0;   " /* if no lock is set, it will btsl (bit set long) */
  30         "    jc lock_loop;          " /* still locked? */
  31         ::"m"(spinlock));
  32 }
  33
  34 void smp_unlock(void)
  35 {
  36     spinlock = 0;       /* unlock */
  37     critical_exit();    /* re-enable interrupts */
  38 }
  39