Re: boost::recursive_mutex for thread-safe logging crashing

From: Ani Taggu (yg-boost-users_at_[hidden])
Date: 2002-09-03 14:39:31

"bill_kempf" <williamkempf_at_[hidden]> wrote in message
news:al2kli+qmrv_at_eGroups.com...
> --- In Boost-Users_at_y..., "Ani Taggu" <yg-boost-users_at_m...> wrote:
> > Hello:
> >
> > I have a simple class to do simple thread-safe logging using
> recursive_mutex
> > as shown below. The problem is, once in a while, it causes any
> thread to die
> > while it tries to log. I haven't been able to isolate why this
> happens. Is
> > recursive_mutex being used correctly?
>
> I'm not sure I can answer why threads would "die".  I'm going to
> assume there's an exception being thrown in the thread, but that's
> just a guess.

Yes the exception thrown is caught in thread_proxy() [thread.cpp] ... btw,
it was difficult for me to figure out that the thread was "dying" because
the exception was being caught using catch (...). Would it help if the
exception was rethrown -- at least for debugging purposes? How else can I
figure out if a boost::thread exited? I am not doing a "join" on the thread
...

>
> I will comment on your logger, though.  It's flawed.  The stream
> library provided on your platform/compiler already provide the level
> of thread synchronization that your logger does.  The problem is
> that this level of thread synchronization granularity is not
> enough.  Consider your use case:
>
> TheLog() << "Hello World" << endl;
>
> The stream is synchronized when outputting "Hello World" and when
> outputting the "endl" manipulator, but not between these two
> seperate calls.  This means your output can be interleaved, and
> basically be unreadable because of this.  You really want to make
> the entire output sequence syncrhonized.
>

Thanks Bill. I understand this. My application is targeted for linux/gcc ,
solaris/SunCC and Windows/MSVC.  Do stream libraries in these platforms
provide the thread synchronization you mentioned?

> I'm also uncertain why you'd use a recursive_mutex in this case?
>

Me too :). It used to be boost::mutex earlier ... then due to some thread
problem (that I don't remember), I made it recursive_mutex .... it worked
fine from then on (until now). Pretty weird reasoning - but time pressure is
a difficult thing to handle :). I can try to reproduce the behavior when
using boost::mutex ....

> Bill Kempf
>
>