Re: [Boost-users] Boost-users Digest, Vol 2579, Issue 2

Subject: Re: [Boost-users] Boost-users Digest, Vol 2579, Issue 2
From: Bogdan Cristea (cristeab_at_[hidden])
Date: 2010-12-21 05:04:21

On Tuesday 21 December 2010 11:55:23 boost-users-request_at_[hidden] 
wrote:
> Hmm, looking into thread.cpp implementation of thread_proxy (callback  
> function for pthread_create()) and boost::thread::join I do not see how  
> this join implementation would work with any abnormal thread termination.
> In thread.cpp boost::thread::join waits the thread termination on line:
> local_thread_info->done_condition.wait(lock);
> 
> The lock gets signaled only at end of thread_proxy(), which is reached  
> only if the user thread routine does "return" or is interrupted with  
> boost::thread means. pthread_exit(), as well as any other emergency  
> termination does only stack unwinding (on most but not all systems), so  
> done_condition is simply never signaled in these circumstances. To be  
> correct the thread_proxy() should have installed cleanup routine with  
> pthread_cleanup_push() and, to be sure, have an local object which  
> destructor would signal done_condition as well, but I do not see it in  
> boost::thread code.
> 
> Bogdan, when you said, the test program works for you - did you means it  
> does return with status 0? If so, I wonder, which way the execution goes  
> in your thread_proxy implementation - can you please debug it a little if  
> you have some time? To build debug version of boost you need to add  
> "variant=debug" option to bjam. I tried the same test program on ubuntu  
> 10.04 TLS with gcc 4.4.3 and boost 1.40 - the same result as with latest  
> boost: it freezes in boost::thread::join() on condition.wait().

Hi

pthread_exit() is used to pass data to the parent thread at exit. 
pthread_join() should receive this data to its second parameter. I will try to 
have a closer look, but I doubt that boost doesn't handle correctly such 
situation.

regards
Bogdan