include/linux/smp_lock.h

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