Re: [PATCH cygport] lib/src_postinst.cygpart: parallelize __prepstrip

[Achim Gratz <Stromeko@nexgo.de>]

Jon Turney via Cygwin-apps writes:
> On 26/03/2023 19:12, Jon Turney via Cygwin-apps wrote:
>>> -        usr/lib/gcc/*/lib*|usr/lib/gcc/*/*.o)
>>> +        usr/lib/gcc/*/*.o)
>> Why this change?

It looks like a mistake that I didn't catch.

>> 
>>> +    local nproc=$(nproc)
>> This limit should probably be taken from the --jobs command line
>> parameter, if specified

Yes, although one could argue that it should actually oversubscribe
since the CPU load per process is expected to be significantly less than
100% per process.

> Looking at this a bit more, a couple of perhaps more serious problems:
>
> * The parallel invocations of __prepstrip_one are all appending to
>   ${T}/.dbgsrc.out
>
> I don't see what makes that safe against interleaving of the output.

Line-buffering and the line being shorter than the buffer should.

> It's probably possible to have each instance write to a separate file
> and collect them together in __prepdebugsrc

Nah, if you insist on making it _really_ safe regardless of line lenght
and buffer size vagaries I'll do file locking on the output file.

> * This patch causes several failures in the testsuite, e.g. with
>   autotools/c testcase.

Which?

> On a brief attempt at debugging, it this looks like it's due to not
> waiting for all the __prepstrip_one to complete before moving on, but
> I think the final wait should prevent that, so idk.

I've seen an indication that the final wait doesn't work, but that is
fixable by a sleep apparently.  Did You see that the process number
limiting doesn't work?

> I'm not clear that invoking 'jobs', is actually doing anything, if
> job-control is turned off in a non-interactive shell?

No, "jobs" shouldn't do anything, but wait should still work I think
(the manpage talks about jobs, but it really means "children").  But
then again, a bit of googling tells me that the bashism "wait -n"
actually needs job control to be enabled, natch.


Regards,
Achim.
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