KernelLand/Kernel/include/rwlock.h

   1 /*
   2  * Acess2 Kernel
   3  *
   4  * rwmutex.c
   5  * - Reader-Writer Mutex (Multiple Readers, One Writer)
   6  */
   7 #ifndef _RWLOCK_H
   8 #define _RWLOCK_H
   9
  10 #include <acess.h>
  11
  12 typedef struct sRWLock  tRWLock;
  13
  14 struct sRWLock
  15 {
  16         tShortSpinlock  Protector;      //!< Protector for the lock strucure
  17         const char      *Name;  //!< Human-readable name
  18          int    Level;  // Number of readers active
  19         struct sThread  *volatile Owner;        //!< Owner of the lock (set upon getting the lock)
  20         struct sThread  *ReaderWaiting;         //!< Waiting threads (readers)
  21         struct sThread  *ReaderWaitingLast;     //!< Waiting threads
  22
  23         struct sThread  *WriterWaiting;         //!< Waiting threads (writers)
  24         struct sThread  *WriterWaitingLast;     //!< Waiting threads
  25 };
  26
  27 /**
  28  * \brief Acquire a read-write lock for reading
  29  * \param Lock Lock to acquire
  30  * \return zero on success, -1 if terminated
  31  *
  32  * Waits until the lock is readable and the increments the reader count
  33  */
  34 extern int      RWLock_AcquireRead(tRWLock *Lock);
  35
  36 /**
  37  * \brief Acquire a read-write lock for writing
  38  * \param Lock Lock to acquire
  39  * \return zero on success, -1 if terminated
  40  *
  41  * Waits until there are no writers, flags all readers to wait, then acquires the lock.
  42  */
  43 extern int      RWLock_AcquireWrite(tRWLock *Lock);
  44
  45 /**
  46  * \brief Release a held rw lock
  47  * \param Lock  Lock to release
  48  * \note Releasing a non-held lock has no effect
  49  */
  50 extern void     RWLock_Release(tRWLock *Lock);
  51
  52 #endif