include/asm-i386/smplock.h

   1 /*
   2  * <asm/smplock.h>
   3  *
   4  * i386 SMP lock implementation
   5  */
   6 #include <linux/interrupt.h>
   7 #include <linux/spinlock.h>
   8 #include <linux/sched.h>
   9 #include <asm/current.h>
  10
  11 extern spinlock_t kernel_flag;
  12
  13 #ifdef CONFIG_SMP
  14 #define kernel_locked()         spin_is_locked(&kernel_flag)
  15 #else
  16 #ifdef CONFIG_PREEMPT
  17 #define kernel_locked()         preempt_count()
  18 #else
  19 #define kernel_locked()         1
  20 #endif
  21 #endif
  22
  23 /*
  24  * Release global kernel lock and global interrupt lock
  25  */
  26 #define release_kernel_lock(task)               \
  27 do {                                            \
  28         if (unlikely(task->lock_depth >= 0))    \
  29                 spin_unlock(&kernel_flag);      \
  30 } while (0)
  31
  32 /*
  33  * Re-acquire the kernel lock
  34  */
  35 #define reacquire_kernel_lock(task)             \
  36 do {                                            \
  37         if (unlikely(task->lock_depth >= 0))    \
  38                 spin_lock(&kernel_flag);        \
  39 } while (0)
  40
  41
  42 /*
  43  * Getting the big kernel lock.
  44  *
  45  * This cannot happen asynchronously,
  46  * so we only need to worry about other
  47  * CPU's.
  48  */
  49 static __inline__ void lock_kernel(void)
  50 {
  51 #ifdef CONFIG_PREEMPT
  52         if (current->lock_depth == -1)
  53                 spin_lock(&kernel_flag);
  54         ++current->lock_depth;
  55 #else
  56 #if 1
  57         if (!++current->lock_depth)
  58                 spin_lock(&kernel_flag);
  59 #else
  60         __asm__ __volatile__(
  61                 "incl %1\n\t"
  62                 "jne 9f"
  63                 spin_lock_string
  64                 "\n9:"
  65                 :"=m" (__dummy_lock(&kernel_flag)),
  66                  "=m" (current->lock_depth));
  67 #endif
  68 #endif
  69 }
  70
  71 static __inline__ void unlock_kernel(void)
  72 {
  73         if (current->lock_depth < 0)
  74                 BUG();
  75 #if 1
  76         if (--current->lock_depth < 0)
  77                 spin_unlock(&kernel_flag);
  78 #else
  79         __asm__ __volatile__(
  80                 "decl %1\n\t"
  81                 "jns 9f\n\t"
  82                 spin_unlock_string
  83                 "\n9:"
  84                 :"=m" (__dummy_lock(&kernel_flag)),
  85                  "=m" (current->lock_depth));
  86 #endif
  87 }