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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|---|---|---|
| .. | ||
| af_rds.c | ||
| bind.c | ||
| cong.c | ||
| connection.c | ||
| ib_cm.c | ||
| ib_rdma.c | ||
| ib_recv.c | ||
| ib_ring.c | ||
| ib_send.c | ||
| ib_stats.c | ||
| ib_sysctl.c | ||
| ib.c | ||
| ib.h | ||
| info.c | ||
| info.h | ||
| iw_cm.c | ||
| iw_rdma.c | ||
| iw_recv.c | ||
| iw_ring.c | ||
| iw_send.c | ||
| iw_stats.c | ||
| iw_sysctl.c | ||
| iw.c | ||
| iw.h | ||
| Kconfig | ||
| loop.c | ||
| loop.h | ||
| Makefile | ||
| message.c | ||
| page.c | ||
| rdma_transport.c | ||
| rdma_transport.h | ||
| rdma.c | ||
| rdma.h | ||
| rds.h | ||
| recv.c | ||
| send.c | ||
| stats.c | ||
| sysctl.c | ||
| tcp_connect.c | ||
| tcp_listen.c | ||
| tcp_recv.c | ||
| tcp_send.c | ||
| tcp_stats.c | ||
| tcp.c | ||
| tcp.h | ||
| threads.c | ||
| transport.c | ||