The message comes if the parallelism of xargs is increased/decreased several times in a short time.
Test case (OpenSuSE 11.4, ext4, xargs from git): mkdir /tmp/test cd /tmp/test dd if=/dev/zero of=1M bs=1M count=1 seq 4000 | ~/git/findutils/inst/bin/xargs -P 2 -n 1 cp 1M & pid=$! sleep 1 while kill -USR2 $pid ; do sleep .1 ; done The following error message appears about every 2-5 seconds, in total 11x out of the 552 times SIGUSR2 has been sent to xargs: /home/berny/git/findutils/inst/bin/xargs: errno-buffer read \ failed in xargs_do_exec (this is probably a bug, please report \ it): Interrupted system call This is hereby reported ;-) Have a nice day, Berny