cgroup_regression_test.sh: fixed test_5
PATCH v3 1/1 cgroup_regression_test.sh: fixed test_5
test_5 checked for possible regressions using a pair of cgroups mounts operations designed to expose a kernel crash; the trigger being the attempt to co-mount and mount the same cgroup subsystem onto two distinct fs hierarchies: the expected failure in the second mount attempt was not properly handled in 2.6.29-rc2 and lead to a kernel crash.
Unfortunately the test assumed that the randomly chosen subsystems were NOT already mounted somewhere when attempting the first co-mount:
this assumption is falsified when userspace is configured to mount all available subsystems at /sysfs on boot (systemd).
So the test was failing straight away during the setup phase:
cgroup_regression_test 5 TFAIL : ltpapicmd.c:188: mount pids and hugetlb failed
Being not trivial to forcibly release and unmount the populated /sysfs cgroups once booted, the script has been reviewed to detect this condition upfront and cope with it dynamically:
- if not already mounted: co-mount + failing mount (as before)
- already mounted: use existing mntpoint + failing co-mount
Since the original fix was on a 2.6.29 kernel the surrounding cgroup code has changed a lot and so the patch was no more trivially 'revertable' for testing purposes: as such this reviewed test script has been verified using a QEMU x86_64 instance running a Kernel 2.6.39 with and without the known fix as detailed in test_5 comments.
--- .../cgroup/cgroup_regression_test.sh | 55 ++++++++++++++----- 1 file changed, 40 insertions(+), 15 deletions(-)
testcases/kernel/controllers/cgroup/cgroup_regression_test.sh +40 -15
@@ -253,6 +253,10 @@ test_4() #--------------------------------------------------------------------------- test_5() { + local mounted + local failing + local mntpoint + lines=`cat /proc/cgroups | wc -l` if [ $lines -le 2 ]; then tst_resm TCONF "require at least 2 cgroup subsystems"
@@ -262,31 +266,51 @@ test_5() subsys1=`tail -n 1 /proc/cgroups | awk '{ print $1 }'` subsys2=`tail -n 2 /proc/cgroups | head -1 | awk '{ print $1 }'` - mount -t cgroup -o $subsys1,$subsys2 xxx cgroup/ - if [ $? -ne 0 ]; then - tst_resm TFAIL "mount $subsys1 and $subsys2 failed" - failed=1 - return + # Accounting here for the fact that the chosen subsystems could + # have been already previously mounted at boot time: in such a + # case we must skip the initial co-mount step (which would + # fail anyway) and properly re-organize the $mntpoint and + # $failing params to be used in the following expected-to-fail + # mount action. Note that the subsysN name itself will be listed + # amongst mounts options. + cat /proc/mounts | grep cgroup | grep -q $subsys1 && mounted=$subsys1 + [ -z "$mounted" ] && cat /proc/mounts | grep cgroup | grep -q $subsys2 && mounted=$subsys2 + if [ -z "$mounted" ]; then + mntpoint=cgroup + failing=$subsys1 + mount -t cgroup -o $subsys1,$subsys2 xxx $mntpoint/ + if [ $? -ne 0 ]; then + tst_resm TFAIL "mount $subsys1 and $subsys2 failed" + failed=1 + return + fi + else + # Use the pre-esistent mountpoint as $mntpoint and use a + # co-mount with $failing: this way the 2nd mount will + # also fail (as expected) in this 'mirrored' configuration. + mntpoint=$(cat /proc/mounts | grep cgroup | grep $mounted | awk '{ print $2 }') + failing=$subsys1,$subsys2 fi - # This 2nd mount should fail - mount -t cgroup -o $subsys1 xxx cgroup/ 2> /dev/null + # This 2nd mount has been properly configured to fail + mount -t cgroup -o $failing xxx $mntpoint/ 2> /dev/null if [ $? -eq 0 ]; then - tst_resm TFAIL "mount $subsys1 should fail" - umount cgroup/ + tst_resm TFAIL "mount $failing should fail" + # Do NOT unmount pre-existent mountpoints... + [ -z "$mounted" ] && umount $mntpoint failed=1 return fi - mkdir cgroup/0 + mkdir $mntpoint/0 # Otherwise we can't attach task if [ "$subsys1" = cpuset -o "$subsys2" = cpuset ]; then - echo 0 > cgroup/0/cpuset.cpus 2> /dev/null - echo 0 > cgroup/0/cpuset.mems 2> /dev/null + echo 0 > $mntpoint/0/cpuset.cpus 2> /dev/null + echo 0 > $mntpoint/0/cpuset.mems 2> /dev/null fi sleep 100 & - echo $! > cgroup/0/tasks + echo $! > $mntpoint/0/tasks check_kernel_bug if [ $? -eq 1 ]; then
@@ -296,8 +320,9 @@ test_5() # clean up /bin/kill -SIGTERM $! > /dev/null wait $! - rmdir cgroup/0 - umount cgroup/ + rmdir $mntpoint/0 + # Do NOT unmount pre-existent mountpoints... + [ -z "$mounted" ] && umount $mntpoint } #---------------------------------------------------------------------------
Signature · 1 line
2.17.1
PATCH v3 1/1 cgroup_regression_test.sh: fixed test_5
Hi Cristian,
thanks for your patch, merged.
Kind regards,
Petr