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 #include <linux/spinlock.h>
   7
   8 #define kernel_locked()         (current->lock_depth >= 0)
   9
  10 extern int __lockfunc __reacquire_kernel_lock(void);
  11 extern 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
  33 static 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
  40 extern void __lockfunc lock_kernel(void)        __acquires(kernel_lock);
  41 extern 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 */