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tcp: fix CONFIG_TCP_MD5SIG + CONFIG_PREEMPT timer BUG()

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I have recently came across a preemption imbalance detected by:

<4>huh, entered ffffffff80644630 with preempt_count 00000102, exited with 00000101?
<0>------------[ cut here ]------------
<2>kernel BUG at /usr/src/linux/kernel/timer.c:664!
<0>invalid opcode: 0000 [1] PREEMPT SMP

with ffffffff80644630 being inet_twdr_hangman().

This appeared after I enabled CONFIG_TCP_MD5SIG and played with it a
bit, so I looked at what might have caused it.

One thing that struck me as strange is tcp_twsk_destructor(), as it
calls tcp_put_md5sig_pool() -- which entails a put_cpu(), causing the
detected imbalance. Found on 2.6.23.9, but 2.6.31 is affected as well,
as far as I can tell.

Signed-off-by: Robert Varga <nite@hq.alert.sk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Robert Varga 2009-09-15 23:49:21 -07:00 committed by David S. Miller
parent 7c64b9f3f5
commit 657e9649e7
1 changed files with 1 additions and 1 deletions
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2
net/ipv4/tcp_minisocks.c
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@ -363,7 +363,7 @@ void tcp_twsk_destructor(struct sock *sk)
#ifdef CONFIG_TCP_MD5SIG
struct tcp_timewait_sock *twsk = tcp_twsk(sk);
if (twsk->tw_md5_keylen)
tcp_put_md5sig_pool();
tcp_free_md5sig_pool();
#endif
}