LCOV - code coverage report
Current view: top level - lkbce/include/linux - rwsem.h (source / functions) Hit Total Coverage
Test: coverage.info Lines: 1 1 100.0 %
Date: 2017-01-25 Functions: 0 0 -

          Line data    Source code
       1             : /* rwsem.h: R/W semaphores, public interface
       2             :  *
       3             :  * Written by David Howells (dhowells@redhat.com).
       4             :  * Derived from asm-i386/semaphore.h
       5             :  */
       6             : 
       7             : #ifndef _LINUX_RWSEM_H
       8             : #define _LINUX_RWSEM_H
       9             : 
      10             : #include <linux/linkage.h>
      11             : 
      12             : #include <linux/types.h>
      13             : #include <linux/kernel.h>
      14             : #include <asm/system.h>
      15             : #include <asm/atomic.h>
      16             : 
      17             : struct rw_semaphore;
      18             : 
      19             : #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
      20             : #include <linux/rwsem-spinlock.h> /* use a generic implementation */
      21             : #else
      22             : #include <asm/rwsem.h> /* use an arch-specific implementation */
      23             : #endif
      24             : 
      25             : /*
      26             :  * lock for reading
      27             :  */
      28             : extern void down_read(struct rw_semaphore *sem);
      29             : 
      30             : /*
      31             :  * trylock for reading -- returns 1 if successful, 0 if contention
      32             :  */
      33             : extern int down_read_trylock(struct rw_semaphore *sem);
      34             : 
      35             : /*
      36             :  * lock for writing
      37             :  */
      38             : extern void down_write(struct rw_semaphore *sem);
      39             : 
      40             : /*
      41             :  * trylock for writing -- returns 1 if successful, 0 if contention
      42             :  */
      43             : extern int down_write_trylock(struct rw_semaphore *sem);
      44             : 
      45             : /*
      46             :  * release a read lock
      47             :  */
      48             : extern void up_read(struct rw_semaphore *sem);
      49             : 
      50             : /*
      51             :  * release a write lock
      52             :  */
      53             : extern void up_write(struct rw_semaphore *sem);
      54             : 
      55             : /*
      56             :  * downgrade write lock to read lock
      57             :  */
      58             : extern void downgrade_write(struct rw_semaphore *sem);
      59           1 : 
      60             : #ifdef CONFIG_DEBUG_LOCK_ALLOC
      61             : /*
      62             :  * nested locking. NOTE: rwsems are not allowed to recurse
      63             :  * (which occurs if the same task tries to acquire the same
      64             :  * lock instance multiple times), but multiple locks of the
      65             :  * same lock class might be taken, if the order of the locks
      66             :  * is always the same. This ordering rule can be expressed
      67             :  * to lockdep via the _nested() APIs, but enumerating the
      68             :  * subclasses that are used. (If the nesting relationship is
      69             :  * static then another method for expressing nested locking is
      70             :  * the explicit definition of lock class keys and the use of
      71             :  * lockdep_set_class() at lock initialization time.
      72             :  * See Documentation/lockdep-design.txt for more details.)
      73             :  */
      74             : extern void down_read_nested(struct rw_semaphore *sem, int subclass);
      75             : extern void down_write_nested(struct rw_semaphore *sem, int subclass);
      76             : /*
      77             :  * Take/release a lock when not the owner will release it.
      78             :  *
      79             :  * [ This API should be avoided as much as possible - the
      80             :  *   proper abstraction for this case is completions. ]
      81             :  */
      82             : extern void down_read_non_owner(struct rw_semaphore *sem);
      83             : extern void up_read_non_owner(struct rw_semaphore *sem);
      84             : #else
      85             : # define down_read_nested(sem, subclass)                down_read(sem)
      86             : # define down_write_nested(sem, subclass)       down_write(sem)
      87             : # define down_read_non_owner(sem)               down_read(sem)
      88             : # define up_read_non_owner(sem)                 up_read(sem)
      89             : #endif
      90             : 
      91             : #endif /* _LINUX_RWSEM_H */

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