arch/x86/lib/cmpxchg.c

   1 /*
   2  * cmpxchg*() fallbacks for CPU not supporting these instructions
   3  */
   4
   5 #include <linux/kernel.h>
   6 #include <linux/smp.h>
   7 #include <linux/module.h>
   8
   9 #ifndef CONFIG_X86_CMPXCHG
  10 unsigned long cmpxchg_386_u8(volatile void *ptr, u8 old, u8 new)
  11 {
  12         u8 prev;
  13         unsigned long flags;
  14
  15         /* Poor man's cmpxchg for 386. Unsuitable for SMP */
  16         local_irq_save(flags);
  17         prev = *(u8 *)ptr;
  18         if (prev == old)
  19                 *(u8 *)ptr = new;
  20         local_irq_restore(flags);
  21         return prev;
  22 }
  23 EXPORT_SYMBOL(cmpxchg_386_u8);
  24
  25 unsigned long cmpxchg_386_u16(volatile void *ptr, u16 old, u16 new)
  26 {
  27         u16 prev;
  28         unsigned long flags;
  29
  30         /* Poor man's cmpxchg for 386. Unsuitable for SMP */
  31         local_irq_save(flags);
  32         prev = *(u16 *)ptr;
  33         if (prev == old)
  34                 *(u16 *)ptr = new;
  35         local_irq_restore(flags);
  36         return prev;
  37 }
  38 EXPORT_SYMBOL(cmpxchg_386_u16);
  39
  40 unsigned long cmpxchg_386_u32(volatile void *ptr, u32 old, u32 new)
  41 {
  42         u32 prev;
  43         unsigned long flags;
  44
  45         /* Poor man's cmpxchg for 386. Unsuitable for SMP */
  46         local_irq_save(flags);
  47         prev = *(u32 *)ptr;
  48         if (prev == old)
  49                 *(u32 *)ptr = new;
  50         local_irq_restore(flags);
  51         return prev;
  52 }
  53 EXPORT_SYMBOL(cmpxchg_386_u32);
  54 #endif