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author | Cong Wang <xiyou.wangcong@gmail.com> | 2017-09-12 02:33:32 +0300 |
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committer | David S. Miller <davem@davemloft.net> | 2017-09-13 06:41:02 +0300 |
commit | 1697c4bb5245649a23f06a144cc38c06715e1b65 (patch) | |
tree | 020f13f2d700eeb85998258429a05d119d689937 /samples/kdb | |
parent | e2ef75445340ca7ec2c4558f84ae6c8c5d650fc8 (diff) | |
download | linux-1697c4bb5245649a23f06a144cc38c06715e1b65.tar.xz |
net_sched: carefully handle tcf_block_put()
As pointed out by Jiri, there is still a race condition between
tcf_block_put() and tcf_chain_destroy() in a RCU callback. There
is no way to make it correct without proper locking or synchronization,
because both operate on a shared list.
Locking is hard, because the only lock we can pick here is a spinlock,
however, in tc_dump_tfilter() we iterate this list with a sleeping
function called (tcf_chain_dump()), which makes using a lock to protect
chain_list almost impossible.
Jiri suggested the idea of holding a refcnt before flushing, this works
because it guarantees us there would be no parallel tcf_chain_destroy()
during the loop, therefore the race condition is gone. But we have to
be very careful with proper synchronization with RCU callbacks.
Suggested-by: Jiri Pirko <jiri@mellanox.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'samples/kdb')
0 files changed, 0 insertions, 0 deletions