08-19-2008
C program
Can anyone tell me how to.....
program to create multiple threads (one master thread and rest worker threads) and using the threads write into and read from shared memory
Restrictions:
Only one thread should be able to read at any instant of time into shared memory region.
Only one thread should be able to write at any instant of time into shared memory region.
Worker threads should inform the master thread after every read and write operation.
Master thread inform the worker thread (which is waiting to acquire shared memory region) that read or write operation is successful and it can acquire the memory for either reading and writing operations.
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LEARN ABOUT OSF1
pthread_rwlock_unlock
pthread_rwlock_unlock(3) Library Functions Manual pthread_rwlock_unlock(3)
NAME
pthread_rwlock_unlock - Unlock a read-write lock.
LIBRARY
DECthreads POSIX 1003.1c Library (libpthread.so)
SYNOPSIS
#include <pthread.h>
int pthread_rwlock_unlock(
pthread_rwlock_t *rwlock);
PARAMETERS
Address of the read-write lock to be unlocked.
DESCRIPTION
This routine releases a lock acquisition held on the read-write lock object referenced by rwlock. Results are undefined if rwlock is not
held by the calling thread.
If this routine is called to release a lock for read access on rwlock and the calling thread also currently holds other locks for read
access on rwlock, the read-write lock object remains in the read locked state. If this routine releases the calling thread's last lock for
read access on rwlock, the calling thread is not longer one of the owners of the lock object.
If this routine is called to release a lock for write access on rwlock, the lock object is put in the unlocked state with no owners.
If a call to this routine results in the read-write lock object becoming unlocked and there are multiple thread waiting to acquire that
lock for write access, DECthreads uses the scheduling policy of those waiting threads to determine which thread next acquires the lock
object for write access. If there are multiple thread waiting to acquire the read-write lock object for read access, DECthreads uses the
scheduling policy of those waiting threads to determine the order in which those threads acquire the lock for read access. If there are
multiple threads waiting to acquire the read-write lock object for both read and write access, it is unspecified whether a thread waiting
for read access or for write access next acquires the lock object.
If the read-write lock object referenced by rwlock is not initialized, the results of calling this routine are undefined.
RETURN VALUES
If an error condition occurs, this routine returns an integer value indicating the type of error. Possible return values are as follows:
Successful completion. The values specified by rwlock does not refer to an initialized read-write lock object. The current thread does
not hold the read-write lock object.
ERRORS
None
RELATED INFORMATION
Functions: pthread_rwlock_init(3), pthread_rwlock_rdlock(3), pthread_rwlock_wrlock(3), pthread_rwlockattr_init(3)
Manuals: Guide to DECthreads and Programmer's Guide
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pthread_rwlock_unlock(3)