Re: possible bug in job control

[Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>]

On Mon, Jul 29, 2013 at 10:47:40PM +0000, Harald van Dijk wrote:
> On 29/07/13 23:44, Luigi Tarenga wrote:
> > hi list,
> > while writing a script to execute parallel ssh command on many host I found
> > a strange behavior of dash. I can replicate it with a very simple script but
> > didn't find any documentation about dash or POSIX that can explain it.
> > 
> > tested on centos 6.4 (dash 0.5.5.1) and wih dash compiled from source (0.5.7)
> > the following script reports error:
> > 
> > #!/bin/dash
> > 
> > sleep 3 &
> > sleep 3 &
> > sleep 3 &
> > sleep 3 &
> > 
> > #/bin/true
> > jobs -l
> > 
> > wait %1
> > wait %2
> > wait %3
> > wait %4
> > 
> > [vortex@lizard ~]$ ./dash-0.5.7/src/dash test.sh
> > [4] + 4569 Running
> > [3] - 4568 Running
> > [2]   4567 Running
> > [1]   4566 Running
> > prova: 14: wait: No such job: %4
> > [vortex@lizard ~]$ echo $?
> > 2
> 
> Yes, this looks like a bug to me. The number of allocated jobs is always
> kept as a multiple of four, and the first check in considering whether
> the job number is valid is "if it's greater than or equal to the number
> of allocated job, it's invalid". That doesn't look right. That would
> only be right if jobs were zero-based, but they aren't. If it's exactly
> equal to the number of available jobs, it can still be valid. It works
> when adding /bin/true, because four more more jobs end up allocated
> internally.
> 
> The attached patch should fix it.
> 
> Cheers,
> Harald

> commit ddeba5485c3309ffc7010f8924d604a781908e1d
> Author: Harald van Dijk <harald@xxxxxxxxxxx>
> Date:   Tue Jul 30 00:36:53 2013 +0200
> 
>     getjob: Fix off-by-one error for multiple of four job numbers

Patch applied.  Thanks!
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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