[Vm-dev] [commit] r2253 - Integrate Henrik Johansen's fix for the nanosleep call in the heartbeat.

[Henrik Sperre Johansen]

  On 13.08.2010 23:14, commits at squeakvm.org wrote:
>
> Author: eliot
> Date: 2010-08-13 14:14:21 -0700 (Fri, 13 Aug 2010)
> New Revision: 2253
>
> Modified:
>     branches/Cog/platforms/unix/vm/sqUnixHeartbeat.c
> Log:
> Integrate Henrik Johansen's fix for the nanosleep call in the heartbeat.
>
>
> Modified: branches/Cog/platforms/unix/vm/sqUnixHeartbeat.c
> ===================================================================
> --- branches/Cog/platforms/unix/vm/sqUnixHeartbeat.c	2010-08-11 18:03:02 UTC (rev 2252)
> +++ branches/Cog/platforms/unix/vm/sqUnixHeartbeat.c	2010-08-13 21:14:21 UTC (rev 2253)
> @@ -607,6 +607,8 @@
>   		struct timespec naptime = beatperiod;
>
>   		while (nanosleep(&naptime,&naptime) == -1
> +			/* oversleeps can return tv_sec = -1 tv_nsec approx 999999999 */
> +			&&  naptime.tv_sec>= 0 /* avoid undoc'ed oversleep behaviour */
>   			&&  (naptime.tv_sec>  0 || naptime.tv_nsec>  MINSLEEPNS)) /*repeat*/
>   			if (errno != EINTR) {
>   				perror("nanosleep");
To be finicky, it's not actually undocumented though, if I interpreted 
the man pages correctly :)
http://www.opengroup.org/onlinepubs/009695399/functions/nanosleep.html
http://developer.apple.com/mac/library/documentation/Darwin/Reference/ManPages/man2/nanosleep.2.html

"If the rmtp argument is non-NULL, the/timespec/ structure referenced by 
it is updated to contain the amount of time remaining in the interval 
(the requested time minus the time actually slept). "

Since it also specifies that the valid range for tv_nsec is 0 - 
999999999, a negative value for tv_sec is the only valid option when it 
has overslept before being interrupted.

Cheers,
Henry
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