f064af1e50
We have for each socket : One spinlock (sk_slock.slock) One rwlock (sk_callback_lock) Possible scenarios are : (A) (this is used in net/sunrpc/xprtsock.c) read_lock(&sk->sk_callback_lock) (without blocking BH) <BH> spin_lock(&sk->sk_slock.slock); ... read_lock(&sk->sk_callback_lock); ... (B) write_lock_bh(&sk->sk_callback_lock) stuff write_unlock_bh(&sk->sk_callback_lock) (C) spin_lock_bh(&sk->sk_slock) ... write_lock_bh(&sk->sk_callback_lock) stuff write_unlock_bh(&sk->sk_callback_lock) spin_unlock_bh(&sk->sk_slock) This (C) case conflicts with (A) : CPU1 [A] CPU2 [C] read_lock(callback_lock) <BH> spin_lock_bh(slock) <wait to spin_lock(slock)> <wait to write_lock_bh(callback_lock)> We have one problematic (C) use case in inet_csk_listen_stop() : local_bh_disable(); bh_lock_sock(child); // spin_lock_bh(&sk->sk_slock) WARN_ON(sock_owned_by_user(child)); ... sock_orphan(child); // write_lock_bh(&sk->sk_callback_lock) lockdep is not happy with this, as reported by Tetsuo Handa It seems only way to deal with this is to use read_lock_bh(callbacklock) everywhere. Thanks to Jarek for pointing a bug in my first attempt and suggesting this solution. Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Tested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Jarek Poplawski <jarkao2@gmail.com> Tested-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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.. | ||
datagram.c | ||
dev_addr_lists.c | ||
dev.c | ||
drop_monitor.c | ||
dst.c | ||
ethtool.c | ||
fib_rules.c | ||
filter.c | ||
flow.c | ||
gen_estimator.c | ||
gen_stats.c | ||
iovec.c | ||
kmap_skb.h | ||
link_watch.c | ||
Makefile | ||
neighbour.c | ||
net_namespace.c | ||
net-sysfs.c | ||
net-sysfs.h | ||
net-traces.c | ||
netevent.c | ||
netpoll.c | ||
pktgen.c | ||
request_sock.c | ||
rtnetlink.c | ||
scm.c | ||
skbuff.c | ||
sock.c | ||
stream.c | ||
sysctl_net_core.c | ||
timestamping.c | ||
user_dma.c | ||
utils.c |