On Tue, May 28, 2019 at 11:29:45AM -0700, Stanislav Fomichev wrote: > Now that we don't have __rcu markers on the bpf_prog_array helpers, > let's use proper rcu_dereference_protected to obtain array pointer > under mutex. > > We also don't need __rcu annotations on cgroup_bpf.inactive since > it's not read/updated concurrently. > > v3: > * amend cgroup_rcu_dereference to include percpu_ref_is_dying; > cgroup_bpf is now reference counted and we don't hold cgroup_mutex > anymore in cgroup_bpf_release > > v2: > * replace xchg with rcu_swap_protected > > Cc: Roman Gushchin <[email protected]> > Signed-off-by: Stanislav Fomichev <[email protected]> > --- > include/linux/bpf-cgroup.h | 2 +- > kernel/bpf/cgroup.c | 32 +++++++++++++++++++++----------- > 2 files changed, 22 insertions(+), 12 deletions(-) > > diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h > index 9f100fc422c3..b631ee75762d 100644 > --- a/include/linux/bpf-cgroup.h > +++ b/include/linux/bpf-cgroup.h > @@ -72,7 +72,7 @@ struct cgroup_bpf { > u32 flags[MAX_BPF_ATTACH_TYPE]; > > /* temp storage for effective prog array used by prog_attach/detach */ > - struct bpf_prog_array __rcu *inactive; > + struct bpf_prog_array *inactive; > > /* reference counter used to detach bpf programs after cgroup removal */ > struct percpu_ref refcnt; > diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c > index d995edbe816d..118b70175dd9 100644 > --- a/kernel/bpf/cgroup.c > +++ b/kernel/bpf/cgroup.c > @@ -22,6 +22,13 @@ > DEFINE_STATIC_KEY_FALSE(cgroup_bpf_enabled_key); > EXPORT_SYMBOL(cgroup_bpf_enabled_key); > > +#define cgroup_rcu_dereference(cgrp, p) > \ > + rcu_dereference_protected(p, lockdep_is_held(&cgroup_mutex) || \ > + percpu_ref_is_dying(&cgrp->bpf.refcnt))
Some comments why percpu_ref_is_dying(&cgrp->bpf.refcnt) is enough here will be appreciated. Thanks!
