Commit 657e9649 authored by Robert Varga's avatar Robert Varga Committed by David S. Miller
Browse files

tcp: fix CONFIG_TCP_MD5SIG + CONFIG_PREEMPT timer BUG()



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: default avatarRobert Varga <nite@hq.alert.sk>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7c64b9f3
...@@ -363,7 +363,7 @@ void tcp_twsk_destructor(struct sock *sk) ...@@ -363,7 +363,7 @@ void tcp_twsk_destructor(struct sock *sk)
#ifdef CONFIG_TCP_MD5SIG #ifdef CONFIG_TCP_MD5SIG
struct tcp_timewait_sock *twsk = tcp_twsk(sk); struct tcp_timewait_sock *twsk = tcp_twsk(sk);
if (twsk->tw_md5_keylen) if (twsk->tw_md5_keylen)
tcp_put_md5sig_pool(); tcp_free_md5sig_pool();
#endif #endif
} }
......
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