include/linux/smp_lock.h

   1 #ifndef __LINUX_SMPLOCK_H
   2 #define __LINUX_SMPLOCK_H
   3
   4 #ifdef CONFIG_LOCK_KERNEL
   5 #include <linux/sched.h>
   6
   7 #define kernel_locked()         (current->lock_depth >= 0)
   8
   9 extern int __lockfunc __reacquire_kernel_lock(void);
  10 extern void __lockfunc __release_kernel_lock(void);
  11
  12 /*
  13  * Release/re-acquire global kernel lock for the scheduler
  14  */
  15 #define release_kernel_lock(tsk) do {           \
  16         if (unlikely((tsk)->lock_depth >= 0))   \
  17                 __release_kernel_lock();        \
  18 } while (0)
  19
  20 /*
  21  * Non-SMP kernels will never block on the kernel lock,
  22  * so we are better off returning a constant zero from
  23  * reacquire_kernel_lock() so that the compiler can see
  24  * it at compile-time.
  25  */
  26 #if defined(CONFIG_SMP) && !defined(CONFIG_PREEMPT_BKL)
  27 # define return_value_on_smp return
  28 #else
  29 # define return_value_on_smp
  30 #endif
  31
  32 static inline int reacquire_kernel_lock(struct task_struct *task)
  33 {
  34         if (unlikely(task->lock_depth >= 0))
  35                 return_value_on_smp __reacquire_kernel_lock();
  36         return 0;
  37 }
  38
  39 extern void __lockfunc lock_kernel(void)        __acquires(kernel_lock);
  40 extern void __lockfunc unlock_kernel(void)      __releases(kernel_lock);
  41
  42 #else
  43
  44 #define lock_kernel()                           do { } while(0)
  45 #define unlock_kernel()                         do { } while(0)
  46 #define release_kernel_lock(task)               do { } while(0)
  47 #define reacquire_kernel_lock(task)             0
  48 #define kernel_locked()                         1
  49
  50 #endif /* CONFIG_LOCK_KERNEL */
  51 #endif /* __LINUX_SMPLOCK_H */