Mailinglist Archive: opensuse-programming (18 mails)

[Per Jessen <per@xxxxxxxxxxxx>]

Roger Oberholtzer wrote:

> On Tue, 2011-04-05 at 16:29 +0200, Roger Oberholtzer wrote:
> > I am using a library that starts lots of threads. It is a proprietary
> > lib and there is no choice as it talks to some company's fancy
> > schmancy hardware.
> >
> > The problem I have is that, it seems (strace is great), this library
> > does not set it up so the threads it creates will not receive
> > signals. In my own much-better-behaved-if-I-do-say-so code, I use
> > pthread_sigmask in the created thread to say that I do not want
> > various signals. Since I see my SIGIO signal delivered to both my
> > thread (really the original process not a thread) or any of the
> > threads created in the library, I think this is what is happening.
> >
> > My question is: how can I turn off delivery of signals to threads I
> > did not create? I basically need to try to do for the threads what
> > they did not do themselves. Add to that: how can a process find out
> > what threads there are? I would imagine that if signal fiddling is
> > even possible, I may need to know this as well.
>
> (Sorry for posting again.)
>
> Instead of trying to figure a way to change a thread's signal
> settings, I have tried setting the process signal mask to block the
> signal I do not want the threads to see before the threads are
> created. After I 'think' the threads have been created, I then set it
> to how I want the parent process to have it. 

Yes, that is how you control the signals for a thread.

> Still, at some point a thread gets my signal. In strace, I only see
> the main process fiddling with threads. It does not look to me like
> any thread is mucking about. 
>
> Is it the case that a thread has to actively change it's signal
> preferences? A change in the parent thread - after the 'child' thread
> is created, should not effect the child thread's signals. Or do I have
> this all wrong?

A thread will inherit the signal mask from the parent at the time of
creation.  A later change in the parent should not affect the child.


/Per Jessen, Zürich

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