On 05/12/2012 19.44, Vicente J. Botet Escriba wrote:
Le 05/12/12 18:49, Gaetano Mendola a écrit :
On 05/12/2012 18.35, Vicente J. Botet Escriba wrote:
Le 05/12/12 16:59, Gaetano Mendola a écrit :
On 05/12/2012 16.29, Vicente Botet wrote:
Gaetano Mendola-3 wrote
On 05/12/2012 13.42, Vicente J. Botet Escriba wrote: > Le 05/12/12 12:33, Gaetano Mendola a écrit : >> On 05/12/2012 09.16, Anthony Williams wrote: >>> On 04/12/12 18:32, Gaetano Mendola wrote: >>>> Hi all, >>>> I was investigating a rare deadlock when issuing an interrupt and >>>> a timed_join in parallel. I come out with the the following code >>>> showing the behavior. >>>> >>>> The deadlock is rare so sometime you need to wait a bit. >>>> >>>> I couldn't try it with boost 1.52 because the code is invalid >>>> due the precondition of "thread joinable" when issuing the >>>> timed_join. >>> >>> That's a hint. >>> >>>> Is the code not valid or a real bug? >>> >>> The code is invalid: you keep trying to interrupt and join even >>> after >>> the thread has been joined! Once the thread has been joined, the >>> thread >>> handle is no longer valid, and you should exit the loop. >> >> I haven't seen this statement in the documentation. >> The loop was meant to exploit exactly this, then you are confirming >> that interrupting a joined thread is not valid. How do I safely >> interrupt then a thread? >> There is no "atomic" check_joinable_then_interrupt, whatching at >> the >> interrupt code it seems that the check is done inside. I'm lost. > Boost.Thread and std::thread are designed so that there is only one > owner of the thread. That is only one thread can join/interrupt a > thread > safely.
Unless I have totally missed it the documentation doesn't mention anything about thread safety (would that be an hint about it?).
From the 1.48 documentation "Member function timed_join()
bool timed_join(const system_time& wait_until);
template<typename TimeDuration> bool timed_join(TimeDuration const& rel_time);
Preconditions:
this->get_id()!=boost::this_thread::get_id()
Postconditions:
If *this refers to a thread of execution on entry, and timed_join returns true, that thread of execution has completed, and *this no longer refers to any thread of execution. If this call to timed_join returns false, *this is unchanged. "
Your second call doesn't satisfy the pre-conditions, so that the outcome of this second call is undefined.
That precondition tests that your are not interrupting yourself doesn't say anything about thread safety. Am I missing something ?
Hi,
no function is considered been thread-safe until it is stated explicitly.
You are completely right, it was my own fault considering it thread safe.
So even thread_group is not thread safe? The implementation is full thread safe. How it is thread-safe? Only one thread can call to the thread_group functions at a time.
The implementation is straight. The boost::thread_group keeps a std::list of boost::threads pointers. the public methods: create_thread add_thread remove_thread join_all interrupt_all size are all protecting the internal status and then all the threads in the list with a common mutex. It appears completely thread safe to me. Regards Gaetano Mendola --