[coreutils] strange behavior of parallel ln across filesystems?

[Peng Yu]

I have the following makefile, which calls ln. The error only shows up
(but not 100% percent of the time) if $(OUTDIR) and the current dir is
not in the same file system (say one is on /dev/sde1 and the other is
on /dev/sdb1). It might be something wrong with the filesystem. But
could you please let me know what might cause ln to generate the
following error? Note that I don't see the error if I remove the
'sleep' command in Makefile, which also seems odd to me.

$ cat Makefile
.PHONY: all

OUTDIR:=/storage/tmp/output
#OUTDIR:=here/output

OUTPUT:=$(OUTDIR)/a.txt $(OUTDIR)/b.txt

all: $(OUTPUT)

$(OUTPUT): $(OUTDIR)/%.txt: input/%.txt
        mkdir -p $(dir $@); touch $@; sleep .001; ln -fs $(dir $@)

clean:
        $(RM) -r $(OUTDIR)

$ make -j2
mkdir -p /storage/tmp/output/; touch /storage/tmp/output/a.txt; sleep
.001; ln -fs /storage/tmp/output/
mkdir -p /storage/tmp/output/; touch /storage/tmp/output/b.txt; sleep
.001; ln -fs /storage/tmp/output/
ln: cannot remove `./output': No such file or directory
make: *** [/storage/tmp/output/b.txt] Error 1
make: *** Waiting for unfinished jobs....


-- 
Regards,
Peng