pg_restore -j mixed and missing lines of output

Hi,

I don't know if this is a known problem, or something I'm doing wrong,
but pg_restore -j tends to sometimes mix lines, or even completely
drop some. Here is an example (it's a -j12 run):

pg_restore: pg_restore: restoring data for table "edw_iu_paglac_axe1_kpi_lac_month_bh"
restoring data for table "edw_iu_paglac_axe1_kpi_lac_month"

This is one case when nothing is lost, messages only get mixed. Sometimes,
entire lines disappear (a table's data is restored, but I don't get the
'restoring' or 'finished' message lines).

This is on Linux, so looking at pg_restore's code, I read that workers are forked
and printing all on the same file descriptor without locking, so I understand
that messages are mixed like this example. I couldn't find any explanation to
the dropped messages though.

Anyway, I don't know if this is a known problem. I searched the mailing list
with no success. I can provide a full log of a complete restore, without and
with -j.

Thanks,

Marc