On Wed, Oct 11, 2017 at 06:39:37AM -0400, Brian Foster wrote: > On Wed, Oct 11, 2017 at 07:00:47PM +1100, Dave Chinner wrote: > > HI folks, > > > > I was wondering if anyone else had seen this problem, because it's > > got me absolutely stumped. One of my test VMs is having a really > > weird livelock in xfs/277. It's getting stuck in an endless loop > > burning the entire CPU in a the 277 process (i.e. running bash). > > What it is stuck on makes no sense to me, nor does the looping > > behaviour, and I can only reproduce it on this one machine. > > > > The code in question: > > > > "fsmap" ) > > testio=`$XFS_IO_PROG -f -c "fsmap" $testfile 2>&1` > > echo $testio | grep -q "Inappropriate ioctl" && \ > > _notrun "xfs_io $command support is missing" > > > > Oh, so it looks like you're in _require_xfs_io_command(). I was hunting > around for this code in xfs/277. :P Oh, sorry, I forgot to paste the function name. > > > Is pretty simple and obvious - not a lot to go wrong. set -x > > shows the last command in the output file to be the fsmap command. > > $test_io has about 5000 lines of output in it. > > > > I did some testing to isolate the problem. This exits having > > executed the fsmap command just fine: > > > > > > "fsmap" ) > > testio=`$XFS_IO_PROG -f -c "fsmap" $testfile 2>&1` > > exit > > > > But this never exits and it starts burning down teh CPU: > > > > "fsmap" ) > > testio=`$XFS_IO_PROG -f -c "fsmap" $testfile 2>&1` > > echo $testio > > exit > > > > Yeah, echoing the output of the fsmap command seems to cause bash to > > enter an endless loop of some kind. Well, it's not endless, because > > every 30s or so the process dies and a new child process runs the > > same loop again. Attaching strace to one of these processes: > > > ... > > > > bash is running around in a tight loop running readdir() on some > > unknown directory over and over again. I can't work it out - this is > > the only machine that does it, and it I can't reproduce it outside > > of running xfs/277 from xfstests... > > > > I'm outta ideas - I've got no idea what the hell is going wrong > > here. Anyone got any ideas? > > > > Heh, that sounds pretty strange. Does your test dev have a pre-existing > $testfile? Nope, the test file is "$pid.xfs_io". I've got several of them in $TEST_DIR from killing tests that hung. > Have you tried to execute the associated code in an > independent bash script? Yes. Doesn't fail from the command line, with unique new files or the files created from _require_xfs_io_command. > E.g., I'd probably try to do something like > mount your test dev then run: > > XFS_IO_PROG=... > testfile=... > > testio=`$XFS_IO_PROG -f -c "fsmap" $testfile 2>&1` > echo $testio > > ... from a separate script using hardcoded values from the xfstests > environment, and see what happens..? ... and it doesn't fail from a #!/bin/bash script. I can only reproduce it from running xfs/277, and only on this machine. That's what's got me stumped. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe fstests" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
