On 05/12/2012 19.57, Vicente J. Botet Escriba wrote:
Le 05/12/12 18:39, Gaetano Mendola a écrit :
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.
My bad. You are right the pre-conditions in 1.48 is not the correct one. I have updated the documentation for join() since 1.50 and since 1.52 for all the other join functions. In particular
Member function |timed_join()|
bool timed_join(const system_time& wait_until);
template<typename TimeDuration> bool timed_join(TimeDuration const& rel_time);
Preconditions:
the thread is joinable.
So you are right there is a bug up to 1.51, with a fix on 1.52.
Sorry for the troubles this issue could caused you.
I believe boost project deserve a wiki documentation site. Gaetano Mendola -- http://cpp-today.blogspot.it/