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genl: Allow concurrent genl callbacks.
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All genl callbacks are serialized by genl-mutex. This can become
bottleneck in multi threaded case.
Following patch adds an parameter to genl_family so that a
particular family can get concurrent netlink callback without
genl_lock held.
New rw-sem is used to protect genl callback from genl family unregister.
in case of parallel_ops genl-family read-lock is taken for callbacks and
write lock is taken for register or unregistration for any family.
In case of locked genl family semaphore and gel-mutex is locked for
any openration.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Pravin B Shelar authored and David S. Miller committed Apr 25, 2013
1 parent 133b942 commit def3117
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Showing 2 changed files with 77 additions and 38 deletions.
1 change: 1 addition & 0 deletions include/net/genetlink.h
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@ struct genl_family {
unsigned int version;
unsigned int maxattr;
bool netnsok;
bool parallel_ops;
int (*pre_doit)(struct genl_ops *ops,
struct sk_buff *skb,
struct genl_info *info);
Expand Down
114 changes: 76 additions & 38 deletions net/netlink/genetlink.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,10 +16,12 @@
#include <linux/skbuff.h>
#include <linux/mutex.h>
#include <linux/bitmap.h>
#include <linux/rwsem.h>
#include <net/sock.h>
#include <net/genetlink.h>

static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */
static DECLARE_RWSEM(cb_lock);

void genl_lock(void)
{
Expand All @@ -41,6 +43,18 @@ int lockdep_genl_is_held(void)
EXPORT_SYMBOL(lockdep_genl_is_held);
#endif

static void genl_lock_all(void)
{
down_write(&cb_lock);
genl_lock();
}

static void genl_unlock_all(void)
{
genl_unlock();
up_write(&cb_lock);
}

#define GENL_FAM_TAB_SIZE 16
#define GENL_FAM_TAB_MASK (GENL_FAM_TAB_SIZE - 1)

Expand Down Expand Up @@ -144,7 +158,7 @@ int genl_register_mc_group(struct genl_family *family,
BUG_ON(grp->name[0] == '\0');
BUG_ON(memchr(grp->name, '\0', GENL_NAMSIZ) == NULL);

genl_lock();
genl_lock_all();

/* special-case our own group */
if (grp == &notify_grp)
Expand Down Expand Up @@ -213,7 +227,7 @@ int genl_register_mc_group(struct genl_family *family,

genl_ctrl_event(CTRL_CMD_NEWMCAST_GRP, grp);
out:
genl_unlock();
genl_unlock_all();
return err;
}
EXPORT_SYMBOL(genl_register_mc_group);
Expand Down Expand Up @@ -255,9 +269,9 @@ static void __genl_unregister_mc_group(struct genl_family *family,
void genl_unregister_mc_group(struct genl_family *family,
struct genl_multicast_group *grp)
{
genl_lock();
genl_lock_all();
__genl_unregister_mc_group(family, grp);
genl_unlock();
genl_unlock_all();
}
EXPORT_SYMBOL(genl_unregister_mc_group);

Expand Down Expand Up @@ -303,9 +317,9 @@ int genl_register_ops(struct genl_family *family, struct genl_ops *ops)
if (ops->policy)
ops->flags |= GENL_CMD_CAP_HASPOL;

genl_lock();
genl_lock_all();
list_add_tail(&ops->ops_list, &family->ops_list);
genl_unlock();
genl_unlock_all();

genl_ctrl_event(CTRL_CMD_NEWOPS, ops);
err = 0;
Expand Down Expand Up @@ -334,16 +348,16 @@ int genl_unregister_ops(struct genl_family *family, struct genl_ops *ops)
{
struct genl_ops *rc;

genl_lock();
genl_lock_all();
list_for_each_entry(rc, &family->ops_list, ops_list) {
if (rc == ops) {
list_del(&ops->ops_list);
genl_unlock();
genl_unlock_all();
genl_ctrl_event(CTRL_CMD_DELOPS, ops);
return 0;
}
}
genl_unlock();
genl_unlock_all();

return -ENOENT;
}
Expand Down Expand Up @@ -373,7 +387,7 @@ int genl_register_family(struct genl_family *family)
INIT_LIST_HEAD(&family->ops_list);
INIT_LIST_HEAD(&family->mcast_groups);

genl_lock();
genl_lock_all();

if (genl_family_find_byname(family->name)) {
err = -EEXIST;
Expand All @@ -394,7 +408,7 @@ int genl_register_family(struct genl_family *family)
goto errout_locked;
}

if (family->maxattr) {
if (family->maxattr && !family->parallel_ops) {
family->attrbuf = kmalloc((family->maxattr+1) *
sizeof(struct nlattr *), GFP_KERNEL);
if (family->attrbuf == NULL) {
Expand All @@ -405,14 +419,14 @@ int genl_register_family(struct genl_family *family)
family->attrbuf = NULL;

list_add_tail(&family->family_list, genl_family_chain(family->id));
genl_unlock();
genl_unlock_all();

genl_ctrl_event(CTRL_CMD_NEWFAMILY, family);

return 0;

errout_locked:
genl_unlock();
genl_unlock_all();
errout:
return err;
}
Expand Down Expand Up @@ -476,7 +490,7 @@ int genl_unregister_family(struct genl_family *family)
{
struct genl_family *rc;

genl_lock();
genl_lock_all();

genl_unregister_mc_groups(family);

Expand All @@ -486,14 +500,14 @@ int genl_unregister_family(struct genl_family *family)

list_del(&rc->family_list);
INIT_LIST_HEAD(&family->ops_list);
genl_unlock();
genl_unlock_all();

kfree(family->attrbuf);
genl_ctrl_event(CTRL_CMD_DELFAMILY, family);
return 0;
}

genl_unlock();
genl_unlock_all();

return -ENOENT;
}
Expand Down Expand Up @@ -530,19 +544,17 @@ void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
}
EXPORT_SYMBOL(genlmsg_put);

static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
static int genl_family_rcv_msg(struct genl_family *family,
struct sk_buff *skb,
struct nlmsghdr *nlh)
{
struct genl_ops *ops;
struct genl_family *family;
struct net *net = sock_net(skb->sk);
struct genl_info info;
struct genlmsghdr *hdr = nlmsg_data(nlh);
struct nlattr **attrbuf;
int hdrlen, err;

family = genl_family_find_byid(nlh->nlmsg_type);
if (family == NULL)
return -ENOENT;

/* this family doesn't exist in this netns */
if (!family->netnsok && !net_eq(net, &init_net))
return -ENOENT;
Expand All @@ -560,26 +572,30 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
return -EPERM;

if (nlh->nlmsg_flags & NLM_F_DUMP) {
struct netlink_dump_control c = {
.dump = ops->dumpit,
.done = ops->done,
};

if (ops->dumpit == NULL)
return -EOPNOTSUPP;

genl_unlock();
{
struct netlink_dump_control c = {
.dump = ops->dumpit,
.done = ops->done,
};
err = netlink_dump_start(net->genl_sock, skb, nlh, &c);
}
genl_lock();
return err;
return netlink_dump_start(net->genl_sock, skb, nlh, &c);
}

if (ops->doit == NULL)
return -EOPNOTSUPP;

if (family->attrbuf) {
err = nlmsg_parse(nlh, hdrlen, family->attrbuf, family->maxattr,
if (family->maxattr && family->parallel_ops) {
attrbuf = kmalloc((family->maxattr+1) *
sizeof(struct nlattr *), GFP_KERNEL);
if (attrbuf == NULL)
return -ENOMEM;
} else
attrbuf = family->attrbuf;

if (attrbuf) {
err = nlmsg_parse(nlh, hdrlen, attrbuf, family->maxattr,
ops->policy);
if (err < 0)
return err;
Expand All @@ -590,7 +606,7 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
info.nlhdr = nlh;
info.genlhdr = nlmsg_data(nlh);
info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
info.attrs = family->attrbuf;
info.attrs = attrbuf;
genl_info_net_set(&info, net);
memset(&info.user_ptr, 0, sizeof(info.user_ptr));

Expand All @@ -605,14 +621,37 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
if (family->post_doit)
family->post_doit(ops, skb, &info);

if (family->parallel_ops)
kfree(attrbuf);

return err;
}

static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
{
struct genl_family *family;
int err;

family = genl_family_find_byid(nlh->nlmsg_type);
if (family == NULL)
return -ENOENT;

if (!family->parallel_ops)
genl_lock();

err = genl_family_rcv_msg(family, skb, nlh);

if (!family->parallel_ops)
genl_unlock();

return err;
}

static void genl_rcv(struct sk_buff *skb)
{
genl_lock();
down_read(&cb_lock);
netlink_rcv_skb(skb, &genl_rcv_msg);
genl_unlock();
up_read(&cb_lock);
}

/**************************************************************************
Expand Down Expand Up @@ -918,7 +957,6 @@ static int __net_init genl_pernet_init(struct net *net)
{
struct netlink_kernel_cfg cfg = {
.input = genl_rcv,
.cb_mutex = &genl_mutex,
.flags = NL_CFG_F_NONROOT_RECV,
};

Expand Down

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