Hello bug-bash readers, in Autoconf, we've stumbled over a problem that has us a bit lost. More precisely, it's output from asynchronous lists that gets lost somewhere. I can't say whether it's due to the shell (it happens with bash, pdksh, zsh, dash), due to the operating system (seen on GNU/Linux, Solaris, and others, or maybe even a simple programming error in our script. But it's annoying as it prevents simple parallelism in a shell-based testsuite framework (Autotest) from working nicely.
Maybe you have an idea where to start looking, that would be great! Below is a couple of scripts that, for me, can seemingly provoke the same failure on a GNU/Linux system (uniprocessor as well as multi). A script output of the original failure can be found here: <http://buildbot.proulx.com:9003/amd64-gnu-linux/builds/961/step-test/0> If you would like to see the original code in action, grab current git Autoconf (you need Autoconf 2.60 preinstalled in order to bootstrap): git clone git://git.savannah.gnu.org/autoconf.git cd autoconf autoreconf -vi ./configure make and run the respective test until it fails: while make check TESTSUITEFLAGS='-k "parallel test execution"'; do :; done then find in tests/testsuite.dir/XXX the remains (XXX being somewhere close to 143). The above seems to fail roughly one out of 10 times or more often. Now, here's the small example that seems to reproduce the original failure (but fails considerably less often): --- foo.sh --- #! /bin/sh do_work () { sleep 1 echo "work $i is done" } for i in 1 2 3 4 5 6 7 8 9 10 do ( do_work $i ) & done wait --- bar.sh --- #! /bin/sh ./foo.sh > stdout 2>stderr echo stdout:; cat stdout test `grep -c done stdout` -eq 10 || { echo "FAILED"; exit 1; } --- Run while ./bar.sh; do :; done You may have to add some load to your system to provoke failure. For example, one failure looked like this: [... lots of output ...] stdout: work 1 is done work 2 is done work 3 is done work 7 is done work 4 is done work 5 is done work 8 is done work 9 is done work 10 is done FAILED another one dropped a lot more, after dozens of iterations: stdout: work 2 is done work 10 is done FAILED Cheers, and thanks for maintaining bash! Ralf
