On Mon, Feb 8, 2021 at 1:00 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Sat, Feb 6, 2021 at 9:06 AM Alexei Starovoitov
> <alexei.starovoitov@xxxxxxxxx> wrote:
> >
> > From: Alexei Starovoitov <ast@xxxxxxxxxx>
> >
> > Since sleepable programs are now executing under migrate_disable
> > the per-cpu maps are safe to use.
Also made me wonder if PERF_EVENT_ARRAY map is usable in sleepable now?
> > The map-in-map were ok to use in sleepable from the time sleepable
> > progs were introduced.
> >
> > Note that non-preallocated maps are still not safe, since there is
> > no rcu_read_lock yet in sleepable programs and dynamically allocated
> > map elements are relying on rcu protection. The sleepable programs
> > have rcu_read_lock_trace instead. That limitation will be addresses
> > in the future.
> >
> > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> > ---
>
> Great.
>
> Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
>
> > kernel/bpf/hashtab.c | 4 ++--
> > kernel/bpf/verifier.c | 7 ++++++-
> > 2 files changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> > index c1ac7f964bc9..d63912e73ad9 100644
> > --- a/kernel/bpf/hashtab.c
> > +++ b/kernel/bpf/hashtab.c
> > @@ -1148,7 +1148,7 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
> > /* unknown flags */
> > return -EINVAL;
> >
> > - WARN_ON_ONCE(!rcu_read_lock_held());
> > + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held());
> >
> > key_size = map->key_size;
> >
> > @@ -1202,7 +1202,7 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
> > /* unknown flags */
> > return -EINVAL;
> >
> > - WARN_ON_ONCE(!rcu_read_lock_held());
> > + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held());
> >
> > key_size = map->key_size;
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 4189edb41b73..9561f2af7710 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -10020,9 +10020,14 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
> > case BPF_MAP_TYPE_HASH:
> > case BPF_MAP_TYPE_LRU_HASH:
> > case BPF_MAP_TYPE_ARRAY:
> > + case BPF_MAP_TYPE_PERCPU_HASH:
> > + case BPF_MAP_TYPE_PERCPU_ARRAY:
> > + case BPF_MAP_TYPE_LRU_PERCPU_HASH:
> > + case BPF_MAP_TYPE_ARRAY_OF_MAPS:
> > + case BPF_MAP_TYPE_HASH_OF_MAPS:
> > if (!is_preallocated_map(map)) {
> > verbose(env,
> > - "Sleepable programs can only use preallocated hash maps\n");
> > + "Sleepable programs can only use preallocated maps\n");
> > return -EINVAL;
> > }
> > break;
> > --
> > 2.24.1
> >
