Re: [boost] [thread 1.48] Multiple interrupt/timed_join leads to deadlock

Subject: Re: [boost] [thread 1.48] Multiple interrupt/timed_join leads to deadlock
From: AntonioM (antomicx_at_[hidden])
Date: 2012-12-06 11:02:14

Hi Vicente,

> [...]
> template<typename  TimeDuration>
> bool  timed_join(TimeDuration  const&  rel_time);
> 
> Preconditions:
> 
>    the thread is joinable.

could you please, then, summarize what is the correct way of coping with
a single thread structure from multiple threads of execution in boost
1.48?

Besides locking it for synchronizing access do you think it would
be safe to access the thread methods like this? (Please don't elaborate
on the specific code choices, I put there some almost non-sense code, 
just to better illustrate my question)

{
end_condition = false
while(not end_condition) {
<get the to_be_joined_thread lock>
if (to_be_joined_thread->joinable()) {
result = 
  to_be_joined_thread->timed_join(<1 second>);
if (result) {
end_condition = true;
}
} else {
end_condition = true;
}
}
}

Suppose at the first round it can't join the thread, after 1 second
it times out, it goes back to the beginning and tries again. Between 
the lock release and the new lock acquisition another thread runs the 
same code and it manages to join the to_be_joined_thread. When the 
first thread gets the lock again, what is it going to find with the 
joinable() call? 
I would expect a joinable() == false, 'cause the thread has been already
joined by someone else. Am I right?

A.