Honored Contributor
Honored Contributor
cyg_mbox_peek (), is always returning the count 1 less than the actual number of messages in the message box. when the message box is empty, then count is returned as 0. why this is so?
i am attaching the code below for reference.
with regards,
sanjay
/* **** include standard header files **** */# include <cyg/kernel/kapi.h># include <cyg/infra/diag.h>
/* **** constants **** */# define true 1
/* size of a task's stack */# define stacksize (cygnum_hal_stack_size_typical + 4096)# define nthreads 2 /* no. of threads */
/* **** user-defined data types **** */
typedef char stack_t; /* each stack entry is 8-bit wide */
/* **** function prototypes **** */
void task_a (cyg_addrword_t);
void task_b (cyg_addrword_t);
/* **** gobal variables **** */
cyg_thread task_housekeeping_info[nthreads];
stack_t task_stack[nthreads+1][stacksize];
cyg_handle_t mbox_handle;
cyg_mbox mbox;
int msg1=12, msg2=24;
/* startup function */
void cyg_user_start ()
{
cyg_handle_t task_handle[nthreads];
cyg_mbox_create (&mbox_handle, &mbox);
cyg_thread_create (0, task_a, (cyg_addrword_t) 0, "task_a",
(void *) task_stack[0], stacksize, &task_handle[0],
&task_housekeeping_info[0]);
cyg_thread_create (0, task_b, (cyg_addrword_t) 1, "task_b",
(void *) task_stack[1], stacksize, &task_handle[1],
&task_housekeeping_info[1]);
cyg_thread_resume (task_handle[0]);
cyg_thread_resume (task_handle[1]);
cyg_scheduler_start ();
}
void task_a (cyg_addrword_t data)
{
cyg_bool_t stat;
long count;
// run this thread forever.
while (true)
{
// delay for 1000 ticks.
cyg_thread_delay (1000);
count = cyg_mbox_peek (mbox_handle);
diag_printf ("count = %ld\n", count);
// send a message to thread b.
cyg_mbox_put (mbox_handle, &msg1);
cyg_mbox_put (mbox_handle, &msg1);
count = cyg_mbox_peek (mbox_handle);
diag_printf ("count = %ld\n", count);
}
}
void task_b (cyg_addrword_t data)
{
void *message;
// run this thread forever.
while (true)
{
// wait for the message.
message = cyg_mbox_get (mbox_handle);
// make sure we received the message before attempting to process it.
if (message != null)
{
// process the message.
diag_printf ("message: %d\n", *((int*)message));
}
}
}
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--- quote end ---
--- Quote End --- Sanjay, have a look on page 75/76 in the "eCos Reference Manual": cyg_mbox_get () is a blocking function. The thread is woken up immediately after the 1. call of cyg_mbox_put () and empties the mailbox. the 2. cyg_mbox_put () increments the counter again to "1". I am using a "timed put " to send and a "try get" to read for not blocking the threads. Also an additional acknowledge flag is usful to synchronize the threads. Regards, Sepp
