On 03/28/2018 09:54 AM, Pintu Kumar wrote:
> Hi,
>
> We are facing one issue on Xenomai-3 on x86_64 system.
> Kernel: 4.9.51
> ipipe version: 4
> # /usr/xenomai/sbin/version
> Xenomai/cobalt v3.0.6 -- #5956064 (2018-03-20 12:13:33 +0100)
>
> Its a very simple API level test.
> We create a condition variable and wait for the condition inside a task.
> Then, we immediately signal the condition from the main thread, and simply
> wait for the test to finish.
>
> But we observed that condition task is never getting released, and the
> program hangs.
>
> This is the output:
> --------------------------
> # ./condsignal
> cond_task --> started
> main --> cond signal success: 0
> Waiting for task to finish....
> ^C
>
>
> This is the code snippet that was used.
> -----------------------------------------------------
> # cat condsignal.c
>
> /*
> * 1. Create an condition variable and wait inside a task.
> * 2. Delete the condition variable from main task.
> * 3. Observe that the condition wait is released and task ends normally.
> * 4. Finally main task should exit normally.
> *
> * */
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/mman.h>
> #include <alchemy/task.h>
> #include <alchemy/mutex.h>
> #include <alchemy/cond.h>
> #include <alchemy/task.h>
>
> static RT_COND cond;
> static RT_MUTEX mutex;
>
> static void cond_task(void *cookie)
> {
> int err;
>
> printf("%s --> started \n", __func__);
> rt_mutex_acquire(&mutex, TM_INFINITE);
> err = rt_cond_wait(&cond, &mutex, TM_INFINITE);
> rt_mutex_release(&mutex);
> if (err) {
> printf("rt_cond_wait failed, err = %d", err);
> return;
> }
> printf("%s --> cond wait done\n", __func__);
> }
>
> int main(int argc, char **argv)
> {
> int err;
> RT_TASK task1;
>
> mlockall(MCL_CURRENT | MCL_FUTURE);
>
> err = rt_mutex_create(&mutex, NULL);
> err = rt_cond_create(&cond, "cond_test");
> err = rt_task_create(&task1, NULL, 0, 99, T_JOINABLE);
> err = rt_task_start(&task1, &cond_task, NULL);
> rt_mutex_acquire(&mutex, TM_INFINITE);
> err = rt_cond_signal(&cond);
> rt_mutex_release(&mutex);
> if (err) {
> printf("Error: rt_cond_signal failed, err = %d", err);
> exit(-1);
> }
> printf("%s --> cond signal success: %d\n", __func__, err);
> printf("Waiting for task to finish....\n");
> rt_task_join(&task1);
>
> return 0;
> }
> -----------------------------------------------------
>
> Is there any fix available in Xenomai-3 for this?
> Please let me know if there is something wrong here.
>
>
You are not using condition variables the right way, those have no
semaphore semantics. Please read a POSIX documentation about them like
[1], the alchemy API does not differ in behavior.
[1] http://pubs.opengroup.org/onlinepubs/7908799/xsh/pthread_cond_wait.html
--
Philippe.
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