On Sun, Oct 29, 2023 at 06:14:31AM +0000, Yafang Shao wrote: > When I initially examined the function current_cgns_cgroup_from_root(), I > was perplexed by its lack of holding cgroup_mutex. However, after Michal > explained the reason[0] to me, I realized that it already holds the > namespace_sem. I believe this intricacy could also confuse others, so it > would be advisable to include an annotation for clarification. > > After we replace the cgroup_mutex with RCU read lock, if current doesn't > hold the namespace_sem, the root cgroup will be NULL. So let's add a > WARN_ON_ONCE() for it. > > [0]. https://lore.kernel.org/bpf/afdnpo3jz2ic2ampud7swd6so5carkilts2mkygcaw67vbw6yh@5b5mncf7qyet > > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx> > Cc: Michal Koutný <mkoutny@xxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun
