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Message-ID: <3B3CCCFF.2329FEDD@kegel.com>
Date: Fri, 29 Jun 2001 11:46:23 -0700
From: Dan Kegel <dank@kegel.com>
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To: Christopher Smith <x@xman.org>,
        "Daniel R. Kegel" <dank@alumni.caltech.edu>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: A signal fairy tale
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Dan Kegel wrote:
> Pseudocode:
> 
>   sigemptyset(&s);
>   sigaddset(SIGUSR1, &s);
>   fd=sigopen(&s);
>   m=read(fd, buf, n*sizeof(siginfo_t))
>   close(fd);
> 
> should probably be equivalent to
> 
>   sigemptyset(&s);
>   sigaddset(SIGUSR1, &s);
>   struct sigaction newaction, oldaction;
>   newaction.sa_handler = dummy_handler;
>   newaction.sa_flags = SA_SIGINFO;
>   newaction.sa_mask = 0;
>   sigaction(SIGUSR1, &newaction, &oldaction);

I forgot to mask off the signal to avoid traditional delivery:

    sigprocmask(SIG_BLOCK, &s, &oldmask);

>   for (i=0; i<n; i++)
>      if (sigwaitinfo(&s, buf+i))
>         break;
>   m = n * sizeof(siginfo_t);
>   sigaction(SIGUSR1, &oldaction, 0);

    sigprocmask(SIG_UNBLOCK, &s);
 
> (apologies if any of the above is wrong)

- Dan