Hi,
The problem is that fifos in init_modules whose pointer you are sending to
start_routine is freed when you leave init_modules (around the time the
start_routine thread is created), so the fifos you are using in
start_routine is actually an unallocated bit of memory (or more likely it
is allocated for something else during the pthread_wait_np since it is
changing).
If you want to pass the same fifos from init_module to start_routine, you
need to explicitly allocate the memory, and then free in in the cleanup at
the end, or use a global variable.
Cheers,
Richard Reeve.
On Fri, 26 Oct 2001, Pablo Alvarez wrote:
> Hi,
>
> I am starting out with rtLinux, and am having a funny problem in a simple
> test program: it looks like after I call pthread_wait_np() for the first
> time, the values of one of my variables change for no reason that I can see.
> I can work around this if I have to, but I would rather not have unsolved
> mysteries, so I would appreciate any advice. It seems likely that I just
> don't understand some feature that I need to learn about.
>
> The module is supposed to write data to an rtfifo and will eventually read
> from a second one, which is why I try to pass an array of two fifo numbers as
> arguments to start_routine. The pointer to the array appears to remain
> unchanged, but the values pointed to do change, although only once. Output
> from dmesg is after the code.
>
> Here is the code. There are a lot of debugging rtl_printfs in it, so you can
> see what happens with dmesg.
>
> #include <rtl.h>
> #include <time.h>
> #include <pthread.h>
> #include <rtl_fifo.h>
>
> pthread_t thread;
>
> void * start_routine(void *arg)
> {
> unsigned int *fifos = (unsigned int *) arg;
> unsigned short values[4] = {0,1,2,3};
> unsigned int counter = 0;
> struct sched_param p;
>
> p . sched_priority = 1;
> pthread_setschedparam (pthread_self(), SCHED_FIFO, &p);
>
> pthread_make_periodic_np (pthread_self(), gethrtime(), 500000000);//0.5
> seconds
>
> rtl_printf("pre-while fifo values are: %u write and %u
> read\n",fifos[0],fifos[1]);
> rtl_printf("pre-while fifo pointer is: %lu\n", (unsigned long) fifos);
>
> while (1)
> {
> rtl_printf("fifo values before pthread_wait_np() are: %u write and %u
> read\n",fifos[0],fifos[1]);
> rtl_printf("fifo pointer before pthread_wait_np() is: %lu\n", (unsigned
> long) fifos);
> ++counter;
> pthread_wait_np ();
> rtl_printf("fifo values after pthread_wait_np() are: %u write and %u
> read\n",fifos[0],fifos[1]);
> rtl_printf("fifo pointer after pthread_wait_np() is: %lu\n", (unsigned
> long) fifos);
> rtf_put(fifos[0],values,4*sizeof(unsigned short));
> rtf_put(0,&counter,sizeof(counter));
> }
> return 0;
> }
>
> int init_module(void)
> {
> unsigned int fifos[2] = {0,1};//write to 0, read from 1
> int i;
> for (i = 0; i < 2; ++i)
> {
> rtf_destroy(fifos[i]);
> rtl_printf("created rtfifo %d: %d\n", fifos[i],
> rtf_create(fifos[i],2048));
> }
> return pthread_create (&thread, NULL, start_routine, (void *)fifos);
> }
>
> void cleanup_module(void)
> {
> unsigned int fifos[2] = {0,1};//write to 0, read from 1
> int i;
> for (i = 0; i < 2; ++i)
> {
> rtl_printf("destroyed rtfifo %d: %d\n", fifos[i],
> rtf_destroy(fifos[i]));
> }
> pthread_delete_np (thread);
> }
>
>
> ---------------Output from dmesg -------------------------
>
> RTLinux Extensions Loaded (http://www.fsmlabs.com/)
> created rtfifo 0: 0
> created rtfifo 1: 0
> pre-while fifo values are: 0 write and 1 read
> pre-while fifo pointer is: 3372441380
> fifo values before pthread_wait_np() are: 0 write and 1 read
> fifo pointer before pthread_wait_np() is: 3372441380
> fifo values after pthread_wait_np() are: 3550217344 write and 128 read
> fifo pointer after pthread_wait_np() is: 3372441380
> fifo values before pthread_wait_np() are: 3550217344 write and 128 read
> fifo pointer before pthread_wait_np() is: 3372441380
> fifo values after pthread_wait_np() are: 3550217344 write and 128 read
> fifo pointer after pthread_wait_np() is: 3372441380
> fifo values before pthread_wait_np() are: 3550217344 write and 128 read
> fifo pointer before pthread_wait_np() is: 3372441380
> destroyed rtfifo 0: 0
> destroyed rtfifo 1: 0
>
> Thanks,
>
> Pablo Alvarez ([EMAIL PROTECTED])
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