• Alexei Starovoitov's avatar
    net_sched: act_bpf: remove spinlock in fast path · cff82457
    Alexei Starovoitov authored
    Similar to act_gact/act_mirred, act_bpf can be lockless in packet processing
    with extra care taken to free bpf programs after rcu grace period.
    Replacement of existing act_bpf (very rare) is done with synchronize_rcu()
    and final destruction is done from tc_action_ops->cleanup() callback that is
    called from tcf_exts_destroy()->tcf_action_destroy()->__tcf_hash_release() when
    bind and refcnt reach zero which is only possible when classifier is destroyed.
    Previous two patches fixed the last two classifiers (tcindex and rsvp) to
    call tcf_exts_destroy() from rcu callback.
    Similar to gact/mirred there is a race between prog->filter and
    prog->tcf_action. Meaning that the program being replaced may use
    previous default action if it happened to return TC_ACT_UNSPEC.
    act_mirred race betwen tcf_action and tcfm_dev is similar.
    In all cases the race is harmless.
    Long term we may want to improve the situation by replacing the whole
    tc_action->priv as single pointer instead of updating inner fields one by one.
    Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
    Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
act_bpf.c 8.73 KB