Determining if HPS Memory is Available for Reuse

After a successful send-type call using HPS memory, the user must wait until the stack is finished with it before reusing it. There are two ways to determine if HPS memory is available for reuse: event semaphores and polling.

To use the event semaphores method, the application must allocate 15 shared event sempahores and pass them on the sysctl() call used to allocate the HPS memory (see the second example under Allocating HPS Memory). When the stack is finished using the HPS memory, it will post any event semaphores corresponding to the 4K blocks that are now free.

To use the polling method, the application calls sysctl() with an array of pointers. The stack will check each pointer, and if the block is in use, will zero the pointer in the array. The polling method may be used even if event semaphores were also allocated for the memory. Following is an example of the polling method:

         long arrayofptrs[15];
         int mib[4];
         unsigned int needed;

         mib[0] = CTL_OS2;
         mib[1] = AF_INET;
         mib[2] = 0;
         mib[3] = OS2_QUERY_MEMMAPIO;
         needed = sizeof(arrayofptrs);

         if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), arrayofptrs,
             &needed, NULL, 0) < 0) {
             psock_errno("sysctl(QUERY_MEMMAPIO)");
             exit(1);
         }
         for (i = 0; i < 15; i++) {
            if (arrayofptrs[i] == 0) {
               /* pointer is in use */
            }
         }