Semaphore support

Hi bjskill,

The sem_init() routine initializes the semaphore object that the first argument points to. So you're passing

in an un-initialized pointer ... and something ends up getting trashed. Try:

/*struct sem_t *msem */

struct sem_t msem

/*if (sem_init(msem, 0, 0) != 0)*/

if (sem_init (&msem, 0, 0) != 0)

printf("Semaphore not initialized\n");

Regards,

--Scott

Hi smcnutt,

I made some errors when I made my original post. When SemInit() is called something seems to get trashed and cause Nios to reboot:

SemInit(myThreadName, &mySem, "mySemaphore");

void SemInit(char *who, sem_t *mSem, char *label)
{
   printf("%s is initializing %s\n", who, label);  // Debug message
   if (sem_init(mSem, 0, 0) != 0)
      printf("Failed when initializing semaphore.\n");  // Error message
   printf("%s has initialized %s\n", who, label);  // Debug message
   return;
}

I don't see either the debug or error messages displayed before the reboot.

Thanks for your help.

I'm not sure if this is the problem, but you may need to turn on IPC support in the kernel in order for semaphore support to work.

Take a look at:

.../altera/kits/nios2/examples/software/linux/apps/samples/thread

for an example of semaphores...

Hi Ken,

I think that might be the problem. However, I only get an "undefined reference to 'sem_init'" error from the linker when DEBUG=1 and it attempts to generate the .gdb file. When DEBUG=0, the linker does not report any errors or warnings when it generates the application.

What path do I need to follow within the kernel configuration menu to check and see if IPC support is turned on? The only choice in the menu options that I found that was related to semaphores is "General Setup --> POSIX message queues". Is that right?

I'll also take a look at those linux examples to make sure I'm initializing the semaphores correctly.

Thanks for your help.

UPDATE: (8/24/05):

I enabled the "General Setup -> POSIX message queues" from the kernel configuration menu, performed a new build, and downloaded the new vmlinux.bin file. However, the application still causes a Nios2 reboot as soon as sem_init() is called. Is there something else I'm missing?