On Fri, Mar 30, 2018 at 12:12 PM, Pintu Kumar <[email protected]> wrote: > On Wed, Mar 28, 2018 at 11:02 PM, Philippe Gerum <[email protected]> wrote: >> On 03/28/2018 07:20 PM, Pintu Kumar wrote: >>> On Wed, Mar 28, 2018 at 8:37 PM, Philippe Gerum <[email protected]> wrote: >>>> 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); >>>> >>>> The line above is redundant with libcobalt inits. But you need: >>>> >>>> err = rt_task_shadow(NULL, "main", <prio>, 0); >>>> ... >>> >>> OK thank you so much for this. I will try it. >>> And, yes I am debugging this issue. >>> I found that rt_cond_wait_timed, did not return from here: >> >> Ok, thanks for looking at this. The issue is that the app is missing the >> call to rt_task_shadow() in the main thread. So that thread receives >> -EPERM from rt_mutex_acquire(), and the rest is a fallout of that >> original error. >> > > Ok, we tried adding rt_task_shadow(NULL, "main", 99, 0), just before > rt_task_create(), > but it did not help. > Still the tasks hangs under rt_cond_wait(). > So, we need to debug further. >
OK. Good news :) I changed as below and it worked. rt_task_shadow(NULL, "main", 98, 0) So, basically, I lowered the priority of main task and the cond_task exited normally this time. This indicates that cond_task should run first, then the main task. But, now the question is: when do we need rt_task_shadow() and why it is important only for this case? We havent added this in any of our previous tests. Is there any side effects of adding this in actual code ? > > Thanks, > Pintu > > >> -- >> Philippe. _______________________________________________ Xenomai mailing list [email protected] https://xenomai.org/mailman/listinfo/xenomai
