[PATCH v2] net: fix sleeping while atomic problem in sock mem_cgroup.

Glauber Costa
2011-12-16T09:10:58Z

Since we can't scan the proto_list to initialize sock cgroups, as it
holds a rwlock, and we also want to keep the code generic enough to
avoid calling the initialization functions of protocols directly,
I propose we keep the interested parties in a separate list. This list
is protected by a mutex so we can sleep and do the necessary allocations.

Also fixes a reference problem found by Randy Dunlap's randconfig.

Signed-off-by: Glauber Costa <glommer@parallels.com>
CC: Hiroyouki Kamezawa <kamezawa.hiroyu@jp.fujitsu.com>
CC: David S. Miller <davem@davemloft.net>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Stephen Rothwell <sfr@canb.auug.org.au>
CC: Randy Dunlap <rdunlap@xenotime.net>
---
include/linux/memcontrol.h | 11 ++++++-
include/net/sock.h | 5 +---
include/net/tcp_memcontrol.h | 2 +
mm/memcontrol.c | 58 ++++++++++++++++++++++++++++++++++++++++++
net/core/sock.c | 42 +++--------------------------
5 files changed, 75 insertions(+), 43 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 9b296ea..e61fabb 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -390,11 +390,13 @@ enum {
OVER_LIMIT,
};

-#ifdef CONFIG_INET
+struct proto;
struct sock;
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
void sock_update_memcg(struct sock *sk);
void sock_release_memcg(struct sock *sk);
+void register_sock_cgroup(struct proto *prot);
+void unregister_sock_cgroup(struct proto *prot);
#else
static inline void sock_update_memcg(struct sock *sk)
{
@@ -402,7 +404,12 @@ static inline void sock_update_memcg(struct sock *sk)
static inline void sock_release_memcg(struct sock *sk)
{
}
+static inline void register_sock_cgroup(struct proto *prot)
+{
+}
+static inline void unregister_sock_cgroup(struct proto *prot)
+{
+}
#endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
-#endif /* CONFIG_INET */
#endif /* _LINUX_MEMCONTROL_H */

diff --git a/include/net/sock.h b/include/net/sock.h
index 6fe0dae..f8237a3 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -64,10 +64,6 @@
#include <net/dst.h>
#include <net/checksum.h>

-struct cgroup;
-struct cgroup_subsys;
-int mem_cgroup_sockets_init(struct cgroup *cgrp, struct cgroup_subsys *ss);
-void mem_cgroup_sockets_destroy(struct cgroup *cgrp, struct cgroup_subsys *ss);
/*
* This structure really needs to be cleaned up.
* Most of it is for TCP, and not used by any of
@@ -858,6 +854,7 @@ struct proto {
void (*destroy_cgroup)(struct cgroup *cgrp,
struct cgroup_subsys *ss);
struct cg_proto *(*proto_cgroup)(struct mem_cgroup *memcg);
+ struct list_head cgroup_node;
#endif
};

diff --git a/include/net/tcp_memcontrol.h b/include/net/tcp_memcontrol.h
index 3512082..5aa7c4b 100644
--- a/include/net/tcp_memcontrol.h
+++ b/include/net/tcp_memcontrol.h
@@ -11,6 +11,8 @@ struct tcp_memcontrol {
int tcp_memory_pressure;
};

+struct cgroup;
+struct cgroup_subsys;
struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg);
int tcp_init_cgroup(struct cgroup *cgrp, struct cgroup_subsys *ss);
void tcp_destroy_cgroup(struct cgroup *cgrp, struct cgroup_subsys *ss);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7266202..1098afe 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4742,6 +4742,64 @@ static struct cftype kmem_cgroup_files[] = {
},
};

+static DEFINE_MUTEX(cgroup_proto_list_lock);
+static LIST_HEAD(cgroup_proto_list);
+
+static int mem_cgroup_sockets_init(struct cgroup *cgrp, struct cgroup_subsys *ss)
+{
+ struct proto *proto;
+ int ret = 0;
+
+ mutex_lock(&cgroup_proto_list_lock);
+ list_for_each_entry(proto, &cgroup_proto_list, cgroup_node) {
+ if (proto->init_cgroup) {
+ ret = proto->init_cgroup(cgrp, ss);
+ if (ret)
+ goto out;
+ }
+ }
+
+ mutex_unlock(&cgroup_proto_list_lock);
+ return ret;
+out:
+ list_for_each_entry_continue_reverse(proto, &cgroup_proto_list, cgroup_node)
+ if (proto->destroy_cgroup)
+ proto->destroy_cgroup(cgrp, ss);
+ mutex_unlock(&cgroup_proto_list_lock);
+ return ret;
+}
+
+static void mem_cgroup_sockets_destroy(struct cgroup *cgrp, struct cgroup_subsys *ss)
+{
+ struct proto *proto;
+
+ mutex_lock(&cgroup_proto_list_lock);
+ list_for_each_entry_reverse(proto, &cgroup_proto_list, cgroup_node)
+ if (proto->destroy_cgroup)
+ proto->destroy_cgroup(cgrp, ss);
+ mutex_unlock(&cgroup_proto_list_lock);
+}
+
+void register_sock_cgroup(struct proto *prot)
+{
+ if (!prot->proto_cgroup)
+ return;
+
+ mutex_lock(&cgroup_proto_list_lock);
+ list_add(&prot->cgroup_node, &cgroup_proto_list);
+ mutex_unlock(&cgroup_proto_list_lock);
+}
+
+void unregister_sock_cgroup(struct proto *prot)
+{
+ if (!prot->proto_cgroup)
+ return;
+
+ mutex_lock(&cgroup_proto_list_lock);
+ list_del(&prot->cgroup_node);
+ mutex_unlock(&cgroup_proto_list_lock);
+}
+
static int register_kmem_files(struct cgroup *cont, struct cgroup_subsys *ss)
{
int ret = 0;
diff --git a/net/core/sock.c b/net/core/sock.c
index 5a6a906..5a56a55 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -139,43 +139,6 @@
static DEFINE_RWLOCK(proto_list_lock);
static LIST_HEAD(proto_list);

-#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
-int mem_cgroup_sockets_init(struct cgroup *cgrp, struct cgroup_subsys *ss)
-{
- struct proto *proto;
- int ret = 0;
-
- read_lock(&proto_list_lock);
- list_for_each_entry(proto, &proto_list, node) {
- if (proto->init_cgroup) {
- ret = proto->init_cgroup(cgrp, ss);
- if (ret)
- goto out;
- }
- }
-
- read_unlock(&proto_list_lock);
- return ret;
-out:
- list_for_each_entry_continue_reverse(proto, &proto_list, node)
- if (proto->destroy_cgroup)
- proto->destroy_cgroup(cgrp, ss);
- read_unlock(&proto_list_lock);
- return ret;
-}
-
-void mem_cgroup_sockets_destroy(struct cgroup *cgrp, struct cgroup_subsys *ss)
-{
- struct proto *proto;
-
- read_lock(&proto_list_lock);
- list_for_each_entry_reverse(proto, &proto_list, node)
- if (proto->destroy_cgroup)
- proto->destroy_cgroup(cgrp, ss);
- read_unlock(&proto_list_lock);
-}
-#endif
-
/*
* Each address family might have different locking rules, so we have
* one slock key per address family:
@@ -2483,6 +2446,9 @@ int proto_register(struct proto *prot, int alloc_slab)
list_add(&prot->node, &proto_list);
assign_proto_idx(prot);
write_unlock(&proto_list_lock);
+
+ register_sock_cgroup(prot);
+
return 0;

out_free_timewait_sock_slab_name:
@@ -2510,6 +2476,8 @@ void proto_unregister(struct proto *prot)
list_del(&prot->node);
write_unlock(&proto_list_lock);

+ unregister_sock_cgroup(prot);
+
if (prot->slab != NULL) {
kmem_cache_destroy(prot->slab);
prot->slab = NULL;
--
1.7.6.4