#include <revolution/os.h>void OSWaitCond (OSCond* cond, OSMutex* mutex); |
Pointer to condition variable. |
|
Pointer to mutex. |
None.
Blocks the calling thread on the condition variable and unlocks the mutex. Must be called by the thread that owns the mutex.
The calling thread is made runnable again by calling the OSSignalCond function. When this function returns, the calling thread will become the owner of the mutex.
Note that the mutex is temporarily unlocked regardless of the number of times this thread may have locked the mutex with the OSLockMutex function. When this thread reacquires the mutex and notification is given of the condition variable (via the OSSignalCond function), the mutex lock count is restored; therefore, each call to the OSLockMutex function must have a corresponding call to the OSUnlockMutex function.
An example of condition variable use is the following bounded buffer program.
u32 Append (u32 item, buffer * buf)
{
OSLockMutex(&buf->mutex);
while (buf->itemCount == MAX_BUF_SIZE)
{
OSWaitCond(buf->bufferNotFullCV, &buf->mutex);
}
// know that the buffer is not full and that I own the mutex
InsertData(item, buf);
OSUnlockMutex(&buf->mutex);
// let any consumers know that the buffer is not empty anymore.
OSSignalCond(&buf->bufferNotEmptyCV);
}u32 Take (u32 * item, buffer * buf)
{
OSLockMutex(&buf->mutex);
while (buf->itemCount == 0)
{
OSWaitCond(buf->bufferNotEmptyCV, &buf->mutex);
}
// know that the buffer is not empty and that I own the mutex
ExtractData(item, buf);
OSUnlockMutex(&buf->mutex);
// let any appenders know that the buffer is not full anymore.
OSSignalCond(&buf->bufferNotFullCV);
}Thread Functions, Thread Synchronization Functions, OSInitCond, OSInitMutex, OSLockMutex, OSSignalCond, OSTryLockMutex, OSUnlockMutex
03/01/2006 Initial version.