Re: [Rd] Sys.sleep() burns up CPU on Solaris 8

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Sat 01 Apr 2006 - 06:48:10 GMT

That looks like a Solaris quirk. Normalization of the values is not required by the POSIX standard, nor by the other implementations we have tested. The Solaris 7 man page does mention the restriction though.

We will change it for 2.3.0, thank you.

On Fri, 31 Mar 2006, Stephen C. Pope wrote:

> I noticed that R was burning up 100% of a CPU when a call to Sys.sleep()
> was made. Upon investigation, I discovered that R_checkActivityEx() in
> src/unix/sys-std.c was putting the entire timeout (in usec) into the
> struct timeval tv_usec member, leaving tv_sec set to 0.
>
> I don't know about other unix variants, but Solaris requires that the
> timeout value be normalized (i.e. 0 <= tv_usec < 1000000). Because a
> value greater than 1000000 was being placed in tv_usec, select() was
> returning an error (EINVAL) immediately, causing R_checkActivityEx() to
> return immediately. This caused do_syssleep() to loop continuously until
> the desired elapsed time had evolved. A rather sleepless sleep ;-).
>
> The following patch against R-2.2.1 fixes the problem. Note that the
> test of the return value for R_SelectEx() was also incorrect; although
> harmless, it was treating the error return (-1) as a successful return.
>
> stephen pope
> scp@predict.com
>
>
> Here's the patch.
>
> build_main@mambo:/vobs/products/R> gdiff -ub src/unix/sys-std.c@@/main/3
> src/unix/sys-std.c
> --- src/unix/sys-std.c@@/main/3 Thu Jan 12 11:39:55 2006
> +++ src/unix/sys-std.c Fri Mar 31 23:12:16 2006
> @@ -294,13 +294,13 @@
> else onintr();
> }
>
> - tv.tv_sec = 0;
> - tv.tv_usec = usec;
> + tv.tv_sec = usec/1000000;
> + tv.tv_usec = usec % 1000000;
> maxfd = setSelectMask(R_InputHandlers, &readMask);
> if (ignore_stdin)
> FD_CLR(fileno(stdin), &readMask);
> if (R_SelectEx(maxfd+1, &readMask, NULL, NULL,
> - (usec >= 0) ? &tv : NULL, intr))
> + (usec >= 0) ? &tv : NULL, intr) > 0)
> return(&readMask);
> else
> return(NULL);
>
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
>

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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Received on Sat Apr 01 17:10:32 2006

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