On 09/14/2017 02:03 PM, Antoine Hoarau wrote:
> Hello,
> I'm porting a library that uses Xenomai 2.6.5 native to 3.0.5 alchemy on an
> x64 Ubuntu 16.04 + Cobalt kernel 4.9.38.
>
> I'm stuck on conditions that do not wait signals to be emitted :
>
> int ret = rt_cond_wait_until(cond, mutex, rt_timer_ns2ticks(abs_time) )
> returns -ETIMEDOUT immediately.
>
>>From the documentation : -ETIMEDOUT is returned if abs_timeout is reached
> before the condition variable is signaled. But I verified that
> rt_timer_ns2ticks(abs_time) > rt_timer_read(), so it should wait.
>
You may want to check your calling args, e.g. wait for a second before
timeout:
ret = rt_cond_wait_until(&cond, &mutex, rt_timer_read() +
1000000000ULL);
if (ret)
error(1, -ret, "rt_cond_wait_until");
> This lead me to beleive that something was wrong with the mutex.
>
I'm unsure to understand why.
> 1) Can rt_cond_wait return -ETIMEDOUT with the mutex ?
> 2) How would you implement a trylock() on a mutex ?
>
> struct RT_MUTEX_INFO info;
> rt_mutex_inquire(mutex, &info );
> RT_TASK no_task = NO_ALCHEMY_TASK;
> rt_task_same(&info.owner,&no_task) == 0 -> not locked !
> --> rt_mutex_acquire(mutex,TM_NONBLOCK)
rt_mutex_acquire(mutex,TM_NONBLOCK) does mean trylock(), you don't need
further checks. Besides, the code above would be racy.
--
Philippe.
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