On Mon, Aug 03, 2026 at 11:39:14PM -0700, Yosry Ahmed <[email protected]> wrote: > > diff --git a/tools/testing/selftests/cgroup/test_zswap.c > > b/tools/testing/selftests/cgroup/test_zswap.c > > index 49b36ee791606..312d51887a1d8 100644 > > --- a/tools/testing/selftests/cgroup/test_zswap.c > > +++ b/tools/testing/selftests/cgroup/test_zswap.c > > @@ -407,8 +407,11 @@ static int test_zswap_writeback(const char *root, bool > > wb) > > * Thus, the parent's setting shall be what's in effect. */ > > if (cg_write(test_group, "memory.zswap.max", "max")) > > goto out; > > - if (cg_write(test_group, "cgroup.subtree_control", "+memory")) > > - goto out; > > + while (cg_write(test_group, "cgroup.subtree_control", "+memory")) { > > + if (errno != EBUSY) > > + goto out; > > + usleep(1000); > > + } > > I would honestly rather create a new cgroup here instead of reusing > the leaf cgroup as a parent, to avoid any subtleties like this in the > future, or even split test_zswap_writeback() into two test cases. I > don't feel strongly though if others think the simple wait here is > enough.
I somewhat agree, I'm not sure whether the recycling brings any signal
to the test.
In the case, the recycling and (re-)enablement is needed, I'd suggest an
explicit check for emptiness, the best of utils arsenal seems:
cg_read_strcmp_wait(test_cgroup, "cgroup.events", "populated 0\n")
Thanks,
Michal
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