On 05/12/2012 18.08, Anthony Williams wrote:
On 05/12/12 15:59, Gaetano Mendola wrote:
On 05/12/2012 16.29, Vicente Botet wrote:
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 ?
Your code had two bugs. Firstly, it called interrupt and timed_join on the same thread object from multiple threads. Secondly, it called interrupt and timed_join in a loop without ever checking the result of timed_join.
Vicente's quote from the docs addresses the second issue: if timed_join returns true then looping round to call interrupt and timed_join again is now a precondition violation, and thus undefined behaviour.
Then I'm not reading well the precondition. this->get_id(): the thread id of the instance on which I'm calling the boost::thread::interrupt(). boost::this_thread::get_id(): gives the caller thread id. from documentation I'm reading that if an instance of boost::thread doesn't refer to a thread of execution then it returns a default-constructed boost::thread::id that represents Not-a-Thread. This means that in case of an already joined thread this->get_id() returns a default-constructed boost::thread::id, how can that be equal to current (caller) thread id? I'm reading the precondition as: "you can not time_join your self" Indeed looking at 1.52 code in the interrupt method I can read: if (this_thread::get_id() == get_id()) { boost::throw_exception( thread_resource_error( system::errc::resource_deadlock_would_occur, "boost thread: trying joining itself")); } **boost thread: trying joining itself** I'm sure I'm still missing something. Regards Gaetano Mendola