[PATCH 1/2] Set default stack size from program environment

[Andreas Jaeger]

On 03/05/2013 02:57 PM, Siddhesh Poyarekar wrote:
> On 2 March 2013 02:32, Roland McGrath <roland@hack.frob.com> wrote:
>> It's worse in some regards and better in others.  Anything overly
>> coarse-grained like system-wide configuration when it can be local
>> per-user or per-process/inherited configuration is worse for the
>> issues of user choice and flexibility.  Conversely, anything only
>> changeable by privileged administrator action rather than inherited
>> from something casually fungible like the environment is better for
>> the issue of security hardening.

Sorry for chiming in late.

> How about something like this:
>
> 1. A /etc/pthreads.conf with hard limits for stack sizes.  Its absence
> means that RLIMIT_STACK is in play
> 2. A per-user .pthreads.conf with user-level overrides for stack sizes
> (default_stack_size=1024K) and/or program-level overrides
> (default_stack_size=/usr/bin/foo:2M)
> 3. An environment variable for process-level overrides.

This would need also a clear semantic: What if both 2 and 3 are used?

>
> That way we include stuff that everyone hates; the magic environment
> variable that you hate and the configuration files that Carlos hates
> and of course, slower start-up time which I'm sure *everyone* will
> hate ;)  However, it would IMO do a better job of providing
> administrative-level adjustment of stack sizes that I attempted
> before.

And doing all of that together is the most flexible way - but it means 
IMHO we have not understood the problem fully.

It's either 2 or 3 - but there should not be two ways for a single user 
to specify the value.

Regarding 1: Doesn't ulimit allow hard limits for stack sizes already?

This kind of different values will be very hard to debug - unless you 
add also some kind of LD_DEBUG=pthread debugging facility that displays 
the values read and the choice made.

Andreas
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