net: Fix percpu counters deadlock

When we converted the protocol atomic counters such as the orphan count and the total socket count deadlocks were introduced due to the mismatch in BH status of the spots that used the percpu counter operations. Based on the diagnosis and patch by Peter Zijlstra, this patch fixes these issues by disabling BH where we may be in process context. Reported-by: Jeff Kirsher <[email protected]> Tested-by: Ingo Molnar <[email protected]> Signed-off-by: Herbert Xu <[email protected]> Signed-off-by: David S. Miller <[email protected]>
mrcsosa · Dec 30, 2008 · eb4dea5 · eb4dea5
1 parent 0f23174
commit eb4dea5
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Showing 6 changed files with 21 additions and 8 deletions.
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
@@ -964,7 +964,6 @@ void dccp_close(struct sock *sk, long timeout)
 	state = sk->sk_state;
 	sock_hold(sk);
 	sock_orphan(sk);
-	percpu_counter_inc(sk->sk_prot->orphan_count);
 
 	/*
 	 * It is the last release_sock in its life. It will remove backlog.
@@ -978,6 +977,8 @@ void dccp_close(struct sock *sk, long timeout)
 	bh_lock_sock(sk);
 	WARN_ON(sock_owned_by_user(sk));
 
+	percpu_counter_inc(sk->sk_prot->orphan_count);
+
 	/* Have we already been destroyed by a softirq or backlog? */
 	if (state != DCCP_CLOSED && sk->sk_state == DCCP_CLOSED)
 		goto out;

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
@@ -633,8 +633,6 @@ void inet_csk_listen_stop(struct sock *sk)
 
 		acc_req = req->dl_next;
 
-		percpu_counter_inc(sk->sk_prot->orphan_count);
-
 		local_bh_disable();
 		bh_lock_sock(child);
 		WARN_ON(sock_owned_by_user(child));
@@ -644,6 +642,8 @@ void inet_csk_listen_stop(struct sock *sk)
 
 		sock_orphan(child);
 
+		percpu_counter_inc(sk->sk_prot->orphan_count);
+
 		inet_csk_destroy_sock(child);
 
 		bh_unlock_sock(child);

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
@@ -38,6 +38,7 @@
 #include <net/tcp.h>
 #include <net/udp.h>
 #include <net/udplite.h>
+#include <linux/bottom_half.h>
 #include <linux/inetdevice.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
@@ -50,13 +51,17 @@
 static int sockstat_seq_show(struct seq_file *seq, void *v)
 {
 	struct net *net = seq->private;
+	int orphans, sockets;
+
+	local_bh_disable();
+	orphans = percpu_counter_sum_positive(&tcp_orphan_count),
+	sockets = percpu_counter_sum_positive(&tcp_sockets_allocated),
+	local_bh_enable();
 
 	socket_seq_show(seq);
 	seq_printf(seq, "TCP: inuse %d orphan %d tw %d alloc %d mem %d\n",
-		   sock_prot_inuse_get(net, &tcp_prot),
-		   (int)percpu_counter_sum_positive(&tcp_orphan_count),
-		   tcp_death_row.tw_count,
-		   (int)percpu_counter_sum_positive(&tcp_sockets_allocated),
+		   sock_prot_inuse_get(net, &tcp_prot), orphans,
+		   tcp_death_row.tw_count, sockets,
 		   atomic_read(&tcp_memory_allocated));
 	seq_printf(seq, "UDP: inuse %d mem %d\n",
 		   sock_prot_inuse_get(net, &udp_prot),

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
@@ -1836,7 +1836,6 @@ void tcp_close(struct sock *sk, long timeout)
 	state = sk->sk_state;
 	sock_hold(sk);
 	sock_orphan(sk);
-	percpu_counter_inc(sk->sk_prot->orphan_count);
 
 	/* It is the last release_sock in its life. It will remove backlog. */
 	release_sock(sk);
@@ -1849,6 +1848,8 @@ void tcp_close(struct sock *sk, long timeout)
 	bh_lock_sock(sk);
 	WARN_ON(sock_owned_by_user(sk));
 
+	percpu_counter_inc(sk->sk_prot->orphan_count);
+
 	/* Have we already been destroyed by a softirq or backlog? */
 	if (state != TCP_CLOSE && sk->sk_state == TCP_CLOSE)
 		goto out;

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
@@ -51,6 +51,7 @@
  */
 
 
+#include <linux/bottom_half.h>
 #include <linux/types.h>
 #include <linux/fcntl.h>
 #include <linux/module.h>
@@ -1797,7 +1798,9 @@ static int tcp_v4_init_sock(struct sock *sk)
 	sk->sk_sndbuf = sysctl_tcp_wmem[1];
 	sk->sk_rcvbuf = sysctl_tcp_rmem[1];
 
+	local_bh_disable();
 	percpu_counter_inc(&tcp_sockets_allocated);
+	local_bh_enable();
 
 	return 0;
 }

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
@@ -23,6 +23,7 @@
  *      2 of the License, or (at your option) any later version.
  */
 
+#include <linux/bottom_half.h>
 #include <linux/module.h>
 #include <linux/errno.h>
 #include <linux/types.h>
@@ -1830,7 +1831,9 @@ static int tcp_v6_init_sock(struct sock *sk)
 	sk->sk_sndbuf = sysctl_tcp_wmem[1];
 	sk->sk_rcvbuf = sysctl_tcp_rmem[1];
 
+	local_bh_disable();
 	percpu_counter_inc(&tcp_sockets_allocated);
+	local_bh_enable();
 
 	return 0;
 }