On Wed, May 22, 2019 at 10:47:24PM -0700, Yonghong Song wrote: > > > On 5/22/19 4:20 PM, Roman Gushchin wrote: > > Add a kselftest to cover bpf auto-detachment functionality. > > The test creates a cgroup, associates some resources with it, > > attaches a couple of bpf programs and deletes the cgroup. > > > > Then it checks that bpf programs are going away in 5 seconds. > > > > Expected output: > > $ ./test_cgroup_attach > > #override:PASS > > #multi:PASS > > #autodetach:PASS > > test_cgroup_attach:PASS > > > > On a kernel without auto-detaching: > > $ ./test_cgroup_attach > > #override:PASS > > #multi:PASS > > #autodetach:FAIL > > test_cgroup_attach:FAIL > > I ran this problem without both old and new kernels and > both get all PASSes. My testing environment is a VM. > Could you specify how to trigger the above failure? Most likely you're running cgroup v1, so the memory controller is not enabled on unified hierarchy. You need to pass "cgroup_no_v1=all systemd.unified_cgroup_hierarchy=1" as boot time options to run fully on cgroup v2. But generally speaking, the lifecycle of a dying cgroup is completely implementation-defined. No guarantees are provided. So false positives are fine here, and shouldn't be considered as something bad. At the end all we want it to detach programs in a reasonable time after rmdir. Btw, thank you for the careful review of the patchset. I'll address your comments, add acks and will send out v3. Thanks!
