Subj : Re: nptl and signals
To   : comp.programming.threads
From : divijbhatt@gmail.com
Date : Tue Jul 26 2005 11:17 pm



Chris Vine wrote:
> divijbhatt@gmail.com wrote:
>
> >
> >
> > Joe Seigh wrote:
> >> divijbhatt@gmail.com wrote:
> >> > Hi,
> >> >      I am masking the  per thread signal mask but when I use sigwait
> >> > the signal will be delivered to the process which in turn delivers the
> >> > signal to the
> >> > threads randomly in a process and that is the rule of NPTL and most
> >> > importantly how signal/sigaction will determine that it is the thread
> >> > to which the signal has to be delivered.
> >> >
> >> No, it's the rules of Posix that apply here.  I don't know why you're
> >> mixing up signals and NPTL.  What are you attempting to do with
> >> signals and threads?
> >>
> > Hi,
> >    See,I whether u r convinced or not that it is the rule of NPTL I am
> > gtng the same behaviour on my linux 2.6.10 kernel on FC2 with glibc
> > 3.3.3
> >
> > 1.I am creating three threads in the main program
> > 2.I and setting the time for each thread in thread function using
> > setitimer()
> > 3.After the expiraton of timer SIGALRM is called which called signal()
> > asynchronously
> > 4.In signal handler function I am setting the flag
> > 5.In main function I am checking that if that flag is 1 then I do some
> > work there and again make that flag 0.
> >
> > But PROBLEM is:------->
> > 1.I am not gtng signals properly in my signal handler function some
> > signals are dropping.The signals are deliverd to the threads randomly.
> >
> > ****I am using sigwait,pthread_sigmask(in main program),sempahore(in
> > signal handler) also.
>
> If you are using sigwait() (which is the best way of dealing with signals in
> a multi-threaded program) why do you have a signal handler?  If you use
> sigwait() then all the threads should be blocked to the signal in question,
> and sigwait() will act on the signal.
>
> There seems to be something wrong with your design.
>
> You may want to look at the documentation for the pthread_sigmask() function
> call at http://www.unix.org/single_unix_specification/ , which gives an
> example of how to program for signals in a multi-threaded program.
>
> This approach will not work correctly with linuxthreads, as it does not
> deliver signals correctly in conformity with POSIX.  However, if you are
> using NPTL it will be OK.
>
> Chris


Hi,
    Chris I have seen that link instead I have put the pthread_sigmask
before creating the threads but my program blocks.So, I put them after
creating the threads where I am checking the flags just before that.
I think there is some problem with design also but tell me I am using
sigwait for blocked signals when those signals will be dilevered to the
calling thread then signal handler function willn't be executed? I am
making the flag 1 in that signal handler function that's why I need
that function to be worked upon.

Divij

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