On Fri, Mar 05, 2021 at 06:07:23PM +0100, Ævar Arnfjörð Bjarmason wrote: > +# Setting SPATCH_XARGS overrides SPATCH_BATCH_SIZE. To get concurrency > +# when targeting a single contrib/coccinelle/%.patch use e.g. "-P" if > +# your xargs(1) supports it: > +# > +# make contrib/coccinelle/strbuf.cocci.patch SPATCH_XARGS="xargs -P 8 -n 8" > +# > +# Or a combination -jN and "xargs -P": > +# > +# make -j4 coccicheck SPATCH_XARGS="xargs -P 2 -n 8" I don't think this is actually safe to do. At least not if you care about the output patch. All of the parallel processes will go to the same output file: > - if test $(SPATCH_BATCH_SIZE) = 0; then \ > - limit=; \ > - else \ > - limit='-n $(SPATCH_BATCH_SIZE)'; \ > - fi; \ > - if ! echo $(COCCI_SOURCES) | xargs $$limit \ > + if ! echo $(COCCI_SOURCES) | $(SPATCH_XARGS) \ > $(SPATCH) --sp-file $< $(SPATCH_FLAGS) \ > >$@+ 2>$@.log; \ > then \ which means they run the risk of getting jumbled racily. It might work OK in practice if the patches are smaller than spatch puts into a single write() call, and what the OS will treat as an atomic file-write (which is really under-specified in POSIX for regular files). -Peff
