Re: SIGTERM ignored before exec race

[Chet Ramey]

On 2/9/13 12:02 AM, Pádraig Brady wrote:
> $ rpm -q kernel glibc bash
> kernel-2.6.40.4-5.fc15.x86_64
> glibc-2.14.1-6.x86_64
> bash-4.2.10-4.fc15.x86_64
> 
> I notice the following will wait for 5 seconds for
> the timeout process to end with SIGALRM, rather than
> immediately due to kill sending the SIGTERM.

I'll take a look at making the race window smaller; there is probably
some code reordering that will have a beneficial effect.

This race exists, to a certain extent, in all Bourne-like shells.  This
problem only happens when run interactively, and it happens because
interactive shells ignore SIGTERM.  No matter how quickly you modify a
child's signal handlers after fork() returns, there's always the chance
that a kernel's scheduling policies or aome global auto-nice of child
or background processes will cause it to happen.

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/