LXR linux/include/linux/smp

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