Changes from 5.2.1 to 5.3 (theads / signal handling)

[Julian Elischer]

Jose Marcio Martins da Cruz wrote:

>Hello,
>
>Julian Elischer wrote:
>  
>
>>Jose Marcio Martins da Cruz wrote:
>>    
>>
>
>  
>
>>>>also, does the child do an exec() after forking?
>>>>        
>>>>
>>>No. The child gets out the father loop and calls another
>>>initialisation function.
>>>      
>>>
>>The Posix spec says that after a fork(0 teh child must do almost nothing
>>before calling exec()
>>and that AT A MAXIMUM it should only call async-safe functions. (i.e.
>>functions that can be called from
>>within signal handlers).
>>    
>>
>
>So, if I understood, the better I can do is, instead of letting the child follow
>a different path after the fork, he shall better do an exec of another thing and
>start a clean process...
>
>  
>

often what is done is to exec itself again with a different argument to 
make it know it is the child.

why do you need to fork? why not just use more threads?

>>There is all sorts of state being kept for the "now non existant"
>>threads in that address space.
>>
>>For example, some of them will still exist if they were stopped in user
>>space at the time,
>>but some of them will not (if tehy were in the kenrel at teh time). In
>>addition,
>>the process will now be marked "non threaded" in the kernel, as it now only
>>has one kernel thread (as specified by posix) so an attempt to schedule
>>another thread
>>from user space will lead to unknown behaviour.  The child will most likely
>>run for a bit and then freeze up or die in some mysterious way. ( sound
>>familiar?).
>>    
>>
>
>Very clear... Even on releases older than 5.3... 8-(
>
>You clarified a bug which was "harassing" me for a very long time...
>
>Can you point me a good doc about threads, signals, and such kind of things in
>FreeBSD context ?
>  
>

I can suggest the threads programming book
Programming with POSIX Threads
by
David R. Butenhof 
<http://btobsearch.barnesandnoble.com/booksearch/results.asp?userid=tj0j4oSCKr&btob=Y&ath=David+R%2E+Butenhof> 



He was the main person behind the posix threads anyhow so he's pretty 
authoratative.

>Thanks very much for all your very helpful hints.
>
>Jose-Marcio
>
>_______________________________________________
>freebsd-threads at freebsd.org mailing list
>http://lists.freebsd.org/mailman/listinfo/freebsd-threads
>To unsubscribe, send any mail to "freebsd-threads-unsubscribe at freebsd.org"
>  
>