On 7/25/12 11:59 AM, Michael Haubenwallner wrote:
>
> On 07/25/2012 04:50 PM, Chet Ramey wrote:
>>> The AIX 6.1 I've debugged on has:
>>> #define CHILD_MAX 128
>>> #define _POSIX_CHILD_MAX 25
>>> sysconf(_SC_CHILD_MAX) = 1024
>
>> Bash prefers sysconf(_SC_CHILD_MAX) and will use it over the other
>> defines (lib/sh/oslib.c:getmaxchild()). I don't know why AIX chooses
>> to return a different value via sysconf than it defines for CHILD_MAX,
>> especially when it seems to use the CHILD_MAX value to decide when it
>> can recycle the PID space.
>
> Well, _SC_CHILD_MAX is documented across platforms as:
> (Linux) "The max number of simultaneous processes per user ID."
> (HP-UX) "Maximum number of simultaneous processes per user ID."
> (Solaris) "Max processes allowed to a UID"
> (AIX) "Specifies the number of simultaneous processes per real user ID."
> (Interix) "Maximum number of simultaneous processes per user ID."
>
> Also, one Linux machine actually shows the _SC_CHILD_MAX value equal to
> kernel.pid_max (32768 here), so even Linux could see this problem in theory,
> because PIDs really are recycled before kernel.pid_max.
That's interesting, since Posix describes sysconf() as simply a way to
retrieve values from limits.h or unistd.h that one wishes to get at
run time rather than compile time. And interesting that it establishes a
correspondence between CHILD_MAX and _SC_CHILD_MAX.
>
>> And I suspect that the single change of significance is to not check
>> against the childmax value when deciding whether or not to look for and
>> remove this pid from the list of saved termination status values.
>
> Agreed - but is this still different to defining RECYCLES_PIDS then?
It is not. It is one of the things that happens when you define
RECYCLES_PIDS. The question is whether or not that is the single thing
that makes a difference in this case. If it is, there is merit in
removing the check against js.c_childmax entirely or making it dependent
on something else.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU c...@case.edu http://cnswww.cns.cwru.edu/~chet/
