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Date: Tue, 20 Feb 2007 23:49:18 -0800 (PST)
From: David Miller <davem@...emloft.net>
To: leigh@...inno.co.uk
Cc: netdev@...r.kernel.org
Subject: Re: Deadlock in MD5 Signature support
From: "Leigh Brown" <leigh@...inno.co.uk>
Date: Sun, 17 Dec 2006 18:13:06 -0000 (GMT)
> It was all going so well, and then it deadlocked. What can be done
> about this?
Sorry for taking so long about this.
The problem is that tcp_md5sig_pool_lock is taken in both
software-interrupt and non-software-interrupt contexts, but
it is always acquired/released using spin_lock/spin_unlock.
The most conservative fix, which I'll use for 2.6.21 and
2.6.x-stable, is the following.
I invite anyone to rewrite this md5 signature pool mutual
exclusion code, it's not exactly the best :-)
Thanks for reporting this problem.
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ac6516c..74c4d10 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2266,12 +2266,12 @@ void tcp_free_md5sig_pool(void)
{
struct tcp_md5sig_pool **pool = NULL;
- spin_lock(&tcp_md5sig_pool_lock);
+ spin_lock_bh(&tcp_md5sig_pool_lock);
if (--tcp_md5sig_users == 0) {
pool = tcp_md5sig_pool;
tcp_md5sig_pool = NULL;
}
- spin_unlock(&tcp_md5sig_pool_lock);
+ spin_unlock_bh(&tcp_md5sig_pool_lock);
if (pool)
__tcp_free_md5sig_pool(pool);
}
@@ -2314,36 +2314,36 @@ struct tcp_md5sig_pool **tcp_alloc_md5sig_pool(void)
int alloc = 0;
retry:
- spin_lock(&tcp_md5sig_pool_lock);
+ spin_lock_bh(&tcp_md5sig_pool_lock);
pool = tcp_md5sig_pool;
if (tcp_md5sig_users++ == 0) {
alloc = 1;
- spin_unlock(&tcp_md5sig_pool_lock);
+ spin_unlock_bh(&tcp_md5sig_pool_lock);
} else if (!pool) {
tcp_md5sig_users--;
- spin_unlock(&tcp_md5sig_pool_lock);
+ spin_unlock_bh(&tcp_md5sig_pool_lock);
cpu_relax();
goto retry;
} else
- spin_unlock(&tcp_md5sig_pool_lock);
+ spin_unlock_bh(&tcp_md5sig_pool_lock);
if (alloc) {
/* we cannot hold spinlock here because this may sleep. */
struct tcp_md5sig_pool **p = __tcp_alloc_md5sig_pool();
- spin_lock(&tcp_md5sig_pool_lock);
+ spin_lock_bh(&tcp_md5sig_pool_lock);
if (!p) {
tcp_md5sig_users--;
- spin_unlock(&tcp_md5sig_pool_lock);
+ spin_unlock_bh(&tcp_md5sig_pool_lock);
return NULL;
}
pool = tcp_md5sig_pool;
if (pool) {
/* oops, it has already been assigned. */
- spin_unlock(&tcp_md5sig_pool_lock);
+ spin_unlock_bh(&tcp_md5sig_pool_lock);
__tcp_free_md5sig_pool(p);
} else {
tcp_md5sig_pool = pool = p;
- spin_unlock(&tcp_md5sig_pool_lock);
+ spin_unlock_bh(&tcp_md5sig_pool_lock);
}
}
return pool;
@@ -2354,11 +2354,11 @@ EXPORT_SYMBOL(tcp_alloc_md5sig_pool);
struct tcp_md5sig_pool *__tcp_get_md5sig_pool(int cpu)
{
struct tcp_md5sig_pool **p;
- spin_lock(&tcp_md5sig_pool_lock);
+ spin_lock_bh(&tcp_md5sig_pool_lock);
p = tcp_md5sig_pool;
if (p)
tcp_md5sig_users++;
- spin_unlock(&tcp_md5sig_pool_lock);
+ spin_unlock_bh(&tcp_md5sig_pool_lock);
return (p ? *per_cpu_ptr(p, cpu) : NULL);
}
-
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