On 08/04/2015 07:09 AM, Alexei Starovoitov wrote:
Similar to act_gact/act_mirred, act_bpf can be lockless in packet processing.
Also 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.
Okay, what happens however, when we have an action attached to a
classifier and do a replace on that action, meaning one CPU is still
executing the filter inside tcf_bpf(), while another one is already
running tcf_bpf_cfg_cleanup() on that prog? Afaik, the schedule_work()
that's called during freeing maps/progs might 'mitigate' this race,
but doesn't give a hard guarantee, right?
Long term we may want to improve the situation by replacing the whole
struct tc_action as single pointer instead of updating inner fields one by one.
Signed-off-by: Alexei Starovoitov <a...@plumgrid.com>
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