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Date: Thu, 21 Sep 2006 18:03:08 -0600
From: Martin Sebor <sebor@roguewave.com>
Organization: Rogue Wave Software
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To: stdcxx-dev@incubator.apache.org
Subject: Re: incorrect runtimes
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Here's another piece of info (just because I like talking to myself
in public): I posted a question about the Solaris behavior to the
OpenSolaris bugs forum:

http://www.opensolaris.org/jive/thread.jspa?threadID=14188

Martin Sebor wrote:
> Martin Sebor wrote:
> 
>> I took a closer look at the output produced by my little test program
>> (after making a small change to it where I moved the sleep(1) call in
>> the parent branch immediately above the waitpid call). Here's the
>> behavior I have observed on each of the following operating systems:
>>
> 
> Here's a corrected interpretation of the results (the corrected
> program is attached):
> 
> AIX:      only immediate children's times are returned
> HP-UX:    only immediate children's times are returned
> IRIX 6.5: only immediate children's times are returned
> Linux:    only immediate children's times are returned
> Solaris:  cumulative times of children and all their
>           descendants are returned
> Tru64:    only immediate children's times are returned
> 
> I was misled by the rapidly decreasing user times in test runs
> that created increasing numbers of grandchildren. The decreasing
> numbers actually make sense since more processes compete for the
> CPU and thus get to use it less time (with the OS spending more
> of its own time switching between them).
> 
> So I guess the only odd duck is Solaris which accumulates the
> time used up by the child's children's despite the fact that
> they were never waited on.
> 
> Martin
> 
> 
> ------------------------------------------------------------------------
> 
> #include <errno.h>
> #include <signal.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <sys/resource.h>
> #include <sys/time.h>
> #include <sys/types.h>
> #include <sys/wait.h>
> #include <unistd.h>
> 
> static void
> print_usage (int who, int status)
> {
>     struct rusage usage = { 0 };
>     getrusage (who, &usage);
>     printf ("child exit status: %d\n"
>             "usr time: %lu.%06lu\n"
>             "sys time: %lu.%06lu\n",
>             status,
>             usage.ru_utime.tv_sec , usage.ru_utime.tv_usec,
>             usage.ru_stime.tv_sec , usage.ru_stime.tv_usec);
> }
> 
> int main (int argc, char *argv[])
> {
>     unsigned long signo = 1 < argc ? strtoul (argv [1], 0, 10) : 0;
>     unsigned long nsec  = 2 < argc ? strtoul (argv [2], 0, 10) : 0;
>     unsigned long nproc = 3 < argc ? strtoul (argv [3], 0, 10) : 0;
>     unsigned long alrm  = 4 < argc ? strtoul (argv [4], 0, 10) : 0;
>     pid_t child_id;
> 
>     printf ("child spawns %lu grandchildren in the same process group\n"
>             "each child process sets a %lu second alarm and loops forever\n"
>             "parent sleeps %lu seconds before sending signal %lu to group\n",
>             nproc, alrm, nsec, signo);
> 
>     child_id = fork ();
> 
>     if (child_id) {
>         int status;
>         sleep (nsec);
>         if (kill (-child_id, signo))
>             fprintf (stderr, "kill(%d, %d) failed: %s\n",
>                      -child_id, signo, strerror (errno));
> 
>         sleep (1);
>         if (0 > waitpid (child_id, &status, 0))
>             fprintf (stderr, "waitpid(%d, %p, 0) failed: %s\n",
>                      child_id, &status, strerror (errno));
> 
>         while (nproc-- && 0 == kill (-child_id, signo));
> 
>         print_usage (RUSAGE_CHILDREN, status);
>     }
>     else {
>         setsid ();
> 
>         if (10 < nproc)
>             nproc = 10;
> 
>         while (nproc--)
>             if (0 == fork ())
>                 break;
> 
>         alarm (alrm);
> 
>         for ( ; ; );
>     }
> 
>     return 0;
> }