include/linux/smp_lock.h

   1 #ifndef __LINUX_SMPLOCK_H
   2 #define __LINUX_SMPLOCK_H
   3
   4 #include <linux/config.h>
   5 #include <linux/sched.h>
   6 #include <linux/spinlock.h>
   7
   8 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
   9
  10 extern spinlock_t kernel_flag;
  11
  12 #define kernel_locked()         (current->lock_depth >= 0)
  13
  14 #define get_kernel_lock()       spin_lock(&kernel_flag)
  15 #define put_kernel_lock()       spin_unlock(&kernel_flag)
  16
  17 /*
  18  * Release global kernel lock.
  19  */
  20 static inline void release_kernel_lock(struct task_struct *task)
  21 {
  22         if (unlikely(task->lock_depth >= 0))
  23                 put_kernel_lock();
  24 }
  25
  26 /*
  27  * Re-acquire the kernel lock
  28  */
  29 static inline void reacquire_kernel_lock(struct task_struct *task)
  30 {
  31         if (unlikely(task->lock_depth >= 0))
  32                 get_kernel_lock();
  33 }
  34
  35 /*
  36  * Getting the big kernel lock.
  37  *
  38  * This cannot happen asynchronously,
  39  * so we only need to worry about other
  40  * CPU's.
  41  */
  42 static inline void lock_kernel(void)
  43 {
  44         int depth = current->lock_depth+1;
  45         if (likely(!depth))
  46                 get_kernel_lock();
  47         current->lock_depth = depth;
  48 }
  49
  50 static inline void unlock_kernel(void)
  51 {
  52         BUG_ON(current->lock_depth < 0);
  53         if (likely(--current->lock_depth < 0))
  54                 put_kernel_lock();
  55 }
  56
  57 #else
  58
  59 #define lock_kernel()                           do { } while(0)
  60 #define unlock_kernel()                         do { } while(0)
  61 #define release_kernel_lock(task)               do { } while(0)
  62 #define reacquire_kernel_lock(task)             do { } while(0)
  63 #define kernel_locked()                         1
  64
  65 #endif /* CONFIG_SMP || CONFIG_PREEMPT */
  66 #endif /* __LINUX_SMPLOCK_H */