On Sun, 9 Jun 2019, Markus Elfring wrote:

> Hello,
>
> The Coccinelle software supports also a variant of parallel data processing
> after the parameter “--jobs” was passed.
> https://github.com/coccinelle/coccinelle/blob/7ec31ed1fadf738bc487ccefdc63bfe0598f44cc/docs/manual/spatch_options.tex#L745
>
> It is nice when it works to distribute analysis on source files to some processors.
> Unfortunately, undesirable software behaviour can be observed if a database
> like “PostgreSQL 11.3-7.1” would be used in such a system configuration.
> Thus I imagine that it can be occasionally appropriate to perform desired
> parallel data processing by the usage of a detailed pipeline instead.
> https://ocaml.github.io/ocamlunix/pipes.html
>
> How do you think about another application for this kind of
> inter-process communication?

When you use -j, you fork processes that thus the child processes write to
a different region of memory than the parent process.

I don't have any interest in connecting Coccinelle to a database, so I'm
not going to spend any time on debugging your issue.  However, if you want
to look into it, this may be the source of the problem.

Maybe you can use a hashtable, then use merge in a finalize, and the write
the information to the database in the parent thread.

The use of merge is illustrated in eg tests/merge_vars.cocci

julia