Categories: Open C | How To | Code Examples

This page was last modified 18:27, 2 October 2007.

From Forum Nokia Wiki

One way to provide synchronization between processes is using semaphore. Here, we should use semaphore to communicate the state of the processes.

In Symbian C++, we achieve this using RSemaphore, RFastLock, RMutex, RCriticalSection, etc.

In Open C, the steps involved in using semaphore to synchronize are as follows:

• Create a semaphore using semget.
• When a process wants to synchronize with some other process, the first process can create the semaphore and set the semval with some condition.
• Once the other process has finished its task, satisfy the condition for which the other process is waiting for.
• Delete the created semaphore.

#include <sys/sem.h>
#define SEM_KEY 1000
int main()
{
   int semid = semget(SEM_KEY, 1, IPC_CREAT);
   int ret = semctl(semid, 0, SETVAL, 1);
   struct sembuf st = {0, 0, 0};
   ret = semop(semid, &st, 1); // process -1 is blocked over here.
   ret = semctl(semid, 1, IPC_RMID);
   return 0;
}

To communicate between the threads, we can use pthread_mutex for synchronization.

Note:There can be many ways of achieving this functionality;So, code snippets of other ways to do this are welcome.

Links

• TSS000574 - Sharing protected kernel resources between processes

• Communication options between Open C engine and S60 UI