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Date: Thu, 6 Dec 2012 16:14:28 -0500
From: Neil Horman <nhorman@...driver.com>
To: Vlad Yasevich <vyasevich@...il.com>
Cc: Thomas Graf <tgraf@...g.ch>, linux-sctp@...r.kernel.org,
netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] sctp: Add RCU protection to
assoc->transport_addr_list
On Thu, Dec 06, 2012 at 03:07:51PM -0500, Vlad Yasevich wrote:
> On 12/06/2012 02:25 PM, Thomas Graf wrote:
> >peer.transport_addr_list is currently only protected by sk_sock
> >which is inpractical to acquire for procfs dumping purposes.
> >
> >This patch adds RCU protection allowing for the procfs readers to
> >enter RCU read-side critical sections.
> >
> >Modification of the list continues to be serialized via sk_lock.
> >
> >V2: Use list_del_rcu() in sctp_association_free() to be safe
> > Skip transports marked dead when dumping for procfs
> >
> >Cc: Vlad Yasevich <vyasevich@...il.com>
> >Cc: Neil Horman <nhorman@...driver.com>
> >Signed-off-by: Thomas Graf <tgraf@...g.ch>
>
> Acked-by: Vlad Yasevich <vyasevich@...il.com>
>
> -vlad
>
Acked-by: Neil Horman <nhorman@...driver.com>
> >---
> > include/net/sctp/structs.h | 2 ++
> > net/sctp/associola.c | 6 +++---
> > net/sctp/proc.c | 14 ++++++++++++--
> > net/sctp/transport.c | 18 +++++++++++++-----
> > 4 files changed, 30 insertions(+), 10 deletions(-)
> >
> >diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> >index 64158aa..5d6987b 100644
> >--- a/include/net/sctp/structs.h
> >+++ b/include/net/sctp/structs.h
> >@@ -948,6 +948,8 @@ struct sctp_transport {
> >
> > /* 64-bit random number sent with heartbeat. */
> > __u64 hb_nonce;
> >+
> >+ struct rcu_head rcu;
> > };
> >
> > struct sctp_transport *sctp_transport_new(struct net *, const union sctp_addr *,
> >diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> >index b1ef3bc..81b1236 100644
> >--- a/net/sctp/associola.c
> >+++ b/net/sctp/associola.c
> >@@ -445,7 +445,7 @@ void sctp_association_free(struct sctp_association *asoc)
> > /* Release the transport structures. */
> > list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
> > transport = list_entry(pos, struct sctp_transport, transports);
> >- list_del(pos);
> >+ list_del_rcu(pos);
> > sctp_transport_free(transport);
> > }
> >
> >@@ -565,7 +565,7 @@ void sctp_assoc_rm_peer(struct sctp_association *asoc,
> > sctp_assoc_update_retran_path(asoc);
> >
> > /* Remove this peer from the list. */
> >- list_del(&peer->transports);
> >+ list_del_rcu(&peer->transports);
> >
> > /* Get the first transport of asoc. */
> > pos = asoc->peer.transport_addr_list.next;
> >@@ -765,7 +765,7 @@ struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
> > peer->state = peer_state;
> >
> > /* Attach the remote transport to our asoc. */
> >- list_add_tail(&peer->transports, &asoc->peer.transport_addr_list);
> >+ list_add_tail_rcu(&peer->transports, &asoc->peer.transport_addr_list);
> > asoc->peer.transport_count++;
> >
> > /* If we do not yet have a primary path, set one. */
> >diff --git a/net/sctp/proc.c b/net/sctp/proc.c
> >index 06b05ee..8c19e97 100644
> >--- a/net/sctp/proc.c
> >+++ b/net/sctp/proc.c
> >@@ -162,15 +162,20 @@ static void sctp_seq_dump_remote_addrs(struct seq_file *seq, struct sctp_associa
> > struct sctp_af *af;
> >
> > primary = &assoc->peer.primary_addr;
> >- list_for_each_entry(transport, &assoc->peer.transport_addr_list,
> >+ rcu_read_lock();
> >+ list_for_each_entry_rcu(transport, &assoc->peer.transport_addr_list,
> > transports) {
> > addr = &transport->ipaddr;
> >+ if (transport->dead)
> >+ continue;
> >+
> > af = sctp_get_af_specific(addr->sa.sa_family);
> > if (af->cmp_addr(addr, primary)) {
> > seq_printf(seq, "*");
> > }
> > af->seq_dump_addr(seq, addr);
> > }
> >+ rcu_read_unlock();
> > }
> >
> > static void * sctp_eps_seq_start(struct seq_file *seq, loff_t *pos)
> >@@ -441,12 +446,16 @@ static int sctp_remaddr_seq_show(struct seq_file *seq, void *v)
> > head = &sctp_assoc_hashtable[hash];
> > sctp_local_bh_disable();
> > read_lock(&head->lock);
> >+ rcu_read_lock();
> > sctp_for_each_hentry(epb, node, &head->chain) {
> > if (!net_eq(sock_net(epb->sk), seq_file_net(seq)))
> > continue;
> > assoc = sctp_assoc(epb);
> >- list_for_each_entry(tsp, &assoc->peer.transport_addr_list,
> >+ list_for_each_entry_rcu(tsp, &assoc->peer.transport_addr_list,
> > transports) {
> >+ if (tsp->dead)
> >+ continue;
> >+
> > /*
> > * The remote address (ADDR)
> > */
> >@@ -492,6 +501,7 @@ static int sctp_remaddr_seq_show(struct seq_file *seq, void *v)
> > }
> > }
> >
> >+ rcu_read_unlock();
> > read_unlock(&head->lock);
> > sctp_local_bh_enable();
> >
> >diff --git a/net/sctp/transport.c b/net/sctp/transport.c
> >index 206cf52..1295aec 100644
> >--- a/net/sctp/transport.c
> >+++ b/net/sctp/transport.c
> >@@ -163,13 +163,11 @@ void sctp_transport_free(struct sctp_transport *transport)
> > sctp_transport_put(transport);
> > }
> >
> >-/* Destroy the transport data structure.
> >- * Assumes there are no more users of this structure.
> >- */
> >-static void sctp_transport_destroy(struct sctp_transport *transport)
> >+static void sctp_transport_destroy_rcu(struct rcu_head *head)
> > {
> >- SCTP_ASSERT(transport->dead, "Transport is not dead", return);
> >+ struct sctp_transport *transport;
> >
> >+ transport = container_of(head, struct sctp_transport, rcu);
> > if (transport->asoc)
> > sctp_association_put(transport->asoc);
> >
> >@@ -180,6 +178,16 @@ static void sctp_transport_destroy(struct sctp_transport *transport)
> > SCTP_DBG_OBJCNT_DEC(transport);
> > }
> >
> >+/* Destroy the transport data structure.
> >+ * Assumes there are no more users of this structure.
> >+ */
> >+static void sctp_transport_destroy(struct sctp_transport *transport)
> >+{
> >+ SCTP_ASSERT(transport->dead, "Transport is not dead", return);
> >+
> >+ call_rcu(&transport->rcu, sctp_transport_destroy_rcu);
> >+}
> >+
> > /* Start T3_rtx timer if it is not already running and update the heartbeat
> > * timer. This routine is called every time a DATA chunk is sent.
> > */
> >
>
>
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