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