root/include/asm-i386/smp_lock.h

/* */

INCLUDED FROM

DEFINITIONS

1. lock_kernel
2. unlock_kernel

   1 #ifndef __I386_SMPLOCK_H
   2 #define __I386_SMPLOCK_H
   3 
   4 #ifdef __SMP__
   5 
   6 /*
   7  *      Locking the kernel 
   8  */
   9  
  10 extern __inline void lock_kernel(void)
     /*  */
  11 {
  12         unsigned long flags;
  13         int proc = smp_processor_id();
  14 
  15         save_flags(flags);
  16         cli();
  17         /* set_bit works atomic in SMP machines */
  18         while(set_bit(0, (void *)&kernel_flag)) 
  19         {
  20                 /*
  21                  *      We just start another level if we have the lock 
  22                  */
  23                 if (proc == active_kernel_processor)
  24                         break;
  25                 do 
  26                 {
  27 #ifdef __SMP_PROF__             
  28                         smp_spins[smp_processor_id()]++;
  29 #endif                  
  30                         /*
  31                          *      Doing test_bit here doesn't lock the bus 
  32                          */
  33                         if (test_bit(proc, (void *)&smp_invalidate_needed))
  34                                 if (clear_bit(proc, (void *)&smp_invalidate_needed))
  35                                         local_invalidate();
  36                 }
  37                 while(test_bit(0, (void *)&kernel_flag));
  38         }
  39         /* 
  40          *      We got the lock, so tell the world we are here and increment
  41          *      the level counter 
  42          */
  43         active_kernel_processor = proc;
  44         kernel_counter++;
  45         restore_flags(flags);
  46 }
  47 
  48 extern __inline void unlock_kernel(void)
     /*  */
  49 {
  50         unsigned long flags;
  51         save_flags(flags);
  52         cli();
  53         /*
  54          *      If it's the last level we have in the kernel, then
  55          *      free the lock 
  56          */
  57         if (kernel_counter == 0)
  58                 panic("Kernel counter wrong.\n"); /* FIXME: Why is kernel_counter sometimes 0 here? */
  59         
  60         if(! --kernel_counter) 
  61         {
  62                 active_kernel_processor = NO_PROC_ID;
  63                 clear_bit(0, (void *)&kernel_flag);
  64         }
  65         restore_flags(flags);
  66 }
  67 
  68 #endif
  69 #endif

/* */