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Re: Interrupted system call on read after ~20 minutes inactivity?

From	"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups	comp.lang.misc, comp.lang.c
Subject	Re: Interrupted system call on read after ~20 minutes inactivity?
Date	2025-10-05 11:43 -0700
Organization	A noiseless patient Spider
Message-ID	<10bue8l$3lp7f$1@dont-email.me> (permalink)
References	<10bpkh1$25arg$1@dont-email.me> <10bpp4n$2l08$1@artemis.inf.ed.ac.uk>

Cross-posted to 2 groups.

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On 10/3/2025 5:18 PM, Richard Tobin wrote:
> In article <10bpkh1$25arg$1@dont-email.me>,
> Janis Papanagnou  <janis_papanagnou+ng@hotmail.com> wrote:
> 
>> In context of a Genie (Algol 68) program, after leaving the
>> terminal some minutes while the program was waiting in a 'read',
>> the program terminated by an interrupt. So I set up this simple
>> call to reproduce it... - it gets interrupted after ~21 minutes
>> of inactivity.
> 
> [...]
> 
>> The maintainer of the Genie system told me that he has no such
>> logic implemented in his tool
> 
> The maintainer is mistaken.
> 
> If you look in a68g-io.c you will see that the function io_read_conv()
> returns -1 if read() returns EINTR more than MAX_RESTART+1 (257) times.

Ohhh. Reminds me of debugging a race condition many years ago that used 
sem_wait. I noticed that it was not looping back around when EINTR was 
encountered.


> 
> If you look in a68-bits.c you will see that setitimer() is called with
> an interval of INTERRUPT_INTERVAL (5) seconds at the start and is
> called again whenever the handler gets run.
> 
> Your read therefore fails after 258*5 = 1290 seconds.
> 
> (The intention of all this seems to be a to implement a cpu time
> limit, but it also has this presumably undesired effect.)
> 
> On a system where read() is automatically restarted after SIGALRM
> is handled, none of this will happen.

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Interrupted system call on read after ~20 minutes inactivity? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-04 00:59 +0200
  Re: Interrupted system call on read after ~20 minutes inactivity? scott@slp53.sl.home (Scott Lurndal) - 2025-10-03 23:31 +0000
    Re: Interrupted system call on read after ~20 minutes inactivity? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-04 01:57 +0200
    Re: Interrupted system call on read after ~20 minutes inactivity? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-10-04 00:28 +0000
      Re: Interrupted system call on read after ~20 minutes inactivity? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-04 02:41 +0200
        Re: Interrupted system call on read after ~20 minutes inactivity? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-10-04 01:07 +0000
      Re: Interrupted system call on read after ~20 minutes inactivity? richard@cogsci.ed.ac.uk (Richard Tobin) - 2025-10-04 01:04 +0000
        Re: Interrupted system call on read after ~20 minutes inactivity? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-10-04 01:23 +0000
        Re: Interrupted system call on read after ~20 minutes inactivity? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-10-04 01:28 +0000
          Re: Interrupted system call on read after ~20 minutes inactivity? scott@slp53.sl.home (Scott Lurndal) - 2025-10-04 02:12 +0000
        Re: Interrupted system call on read after ~20 minutes inactivity? Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-10-04 02:35 +0000
        Re: Interrupted system call on read after ~20 minutes inactivity? richard@cogsci.ed.ac.uk (Richard Tobin) - 2025-10-04 12:52 +0000
          Re: Interrupted system call on read after ~20 minutes inactivity? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-10-04 18:50 +0000
  Re: Interrupted system call on read after ~20 minutes inactivity? Alan Bawden <alan@csail.mit.edu> - 2025-10-03 19:33 -0400
    Re: Interrupted system call on read after ~20 minutes inactivity? Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-10-03 23:54 +0000
    Re: Interrupted system call on read after ~20 minutes inactivity? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-04 02:00 +0200
      Re: Interrupted system call on read after ~20 minutes inactivity? Alan Bawden <alan@csail.mit.edu> - 2025-10-03 20:26 -0400
        Re: Interrupted system call on read after ~20 minutes inactivity? richard@cogsci.ed.ac.uk (Richard Tobin) - 2025-10-05 11:39 +0000
          Re: Interrupted system call on read after ~20 minutes inactivity? Alan Bawden <alan@csail.mit.edu> - 2025-10-06 04:05 -0400
            Re: Interrupted system call on read after ~20 minutes inactivity? richard@cogsci.ed.ac.uk (Richard Tobin) - 2025-10-06 10:46 +0000
            Re: Interrupted system call on read after ~20 minutes inactivity? Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-10-06 22:04 +0000
  Re: Interrupted system call on read after ~20 minutes inactivity? richard@cogsci.ed.ac.uk (Richard Tobin) - 2025-10-04 00:18 +0000
    Re: Interrupted system call on read after ~20 minutes inactivity? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-04 02:27 +0200
    Re: Interrupted system call on read after ~20 minutes inactivity? scott@slp53.sl.home (Scott Lurndal) - 2025-10-04 02:13 +0000
    Re: Interrupted system call on read after ~20 minutes inactivity? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-10-05 11:43 -0700
  Re: Interrupted system call on read after ~20 minutes inactivity? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-07 16:29 +0200

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