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connector: convert to synchronous netlink message processing
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Commits 01a16b2 (netlink: kill eff_cap from struct netlink_skb_parms)
and c53fa1e (netlink: kill loginuid/sessionid/sid members from struct
netlink_skb_parms) removed some members from struct netlink_skb_parms
that depend on the current context, all netlink users are now required
to do synchronous message processing.

connector however queues received messages and processes them in a work
queue, which is not valid anymore. This patch converts connector to do
synchronous message processing by invoking the registered callback handler
directly from the netlink receive function.

In order to avoid invoking the callback with connector locks held, a
reference count is added to struct cn_callback_entry, the reference
is taken when finding a matching callback entry on the device's queue_list
and released after the callback handler has been invoked.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
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@kaber @davem330
kaber authored and davem330 committed Mar 31, 2011
1 parent e2666f8 commit 04f482f
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Showing 3 changed files with 32 additions and 89 deletions.
58 changes: 17 additions & 41 deletions drivers/connector/cn_queue.c
View file
Expand Up @@ -31,24 +31,9 @@
#include <linux/connector.h>
#include <linux/delay.h>

void cn_queue_wrapper(struct work_struct *work)
{
struct cn_callback_entry *cbq =
container_of(work, struct cn_callback_entry, work);
struct cn_callback_data *d = &cbq->data;
struct cn_msg *msg = NLMSG_DATA(nlmsg_hdr(d->skb));
struct netlink_skb_parms *nsp = &NETLINK_CB(d->skb);

d->callback(msg, nsp);

kfree_skb(d->skb);
d->skb = NULL;

kfree(d->free);
}

static struct cn_callback_entry *
cn_queue_alloc_callback_entry(const char *name, struct cb_id *id,
cn_queue_alloc_callback_entry(struct cn_queue_dev *dev, const char *name,
struct cb_id *id,
void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
{
struct cn_callback_entry *cbq;
Expand All @@ -59,17 +44,23 @@ cn_queue_alloc_callback_entry(const char *name, struct cb_id *id,
return NULL;
}

atomic_set(&cbq->refcnt, 1);

atomic_inc(&dev->refcnt);
cbq->pdev = dev;

snprintf(cbq->id.name, sizeof(cbq->id.name), "%s", name);
memcpy(&cbq->id.id, id, sizeof(struct cb_id));
cbq->data.callback = callback;

INIT_WORK(&cbq->work, &cn_queue_wrapper);
cbq->callback = callback;
return cbq;
}

static void cn_queue_free_callback(struct cn_callback_entry *cbq)
void cn_queue_release_callback(struct cn_callback_entry *cbq)
{
flush_workqueue(cbq->pdev->cn_queue);
if (!atomic_dec_and_test(&cbq->refcnt))
return;

atomic_dec(&cbq->pdev->refcnt);
kfree(cbq);
}

Expand All @@ -85,13 +76,10 @@ int cn_queue_add_callback(struct cn_queue_dev *dev, const char *name,
struct cn_callback_entry *cbq, *__cbq;
int found = 0;

cbq = cn_queue_alloc_callback_entry(name, id, callback);
cbq = cn_queue_alloc_callback_entry(dev, name, id, callback);
if (!cbq)
return -ENOMEM;

atomic_inc(&dev->refcnt);
cbq->pdev = dev;

spin_lock_bh(&dev->queue_lock);
list_for_each_entry(__cbq, &dev->queue_list, callback_entry) {
if (cn_cb_equal(&__cbq->id.id, id)) {
Expand All @@ -104,8 +92,7 @@ int cn_queue_add_callback(struct cn_queue_dev *dev, const char *name,
spin_unlock_bh(&dev->queue_lock);

if (found) {
cn_queue_free_callback(cbq);
atomic_dec(&dev->refcnt);
cn_queue_release_callback(cbq);
return -EINVAL;
}

Expand All @@ -130,10 +117,8 @@ void cn_queue_del_callback(struct cn_queue_dev *dev, struct cb_id *id)
}
spin_unlock_bh(&dev->queue_lock);

if (found) {
cn_queue_free_callback(cbq);
atomic_dec(&dev->refcnt);
}
if (found)
cn_queue_release_callback(cbq);
}

struct cn_queue_dev *cn_queue_alloc_dev(const char *name, struct sock *nls)
Expand All @@ -151,22 +136,13 @@ struct cn_queue_dev *cn_queue_alloc_dev(const char *name, struct sock *nls)

dev->nls = nls;

dev->cn_queue = alloc_ordered_workqueue(dev->name, 0);
if (!dev->cn_queue) {
kfree(dev);
return NULL;
}

return dev;
}

void cn_queue_free_dev(struct cn_queue_dev *dev)
{
struct cn_callback_entry *cbq, *n;

flush_workqueue(dev->cn_queue);
destroy_workqueue(dev->cn_queue);

spin_lock_bh(&dev->queue_lock);
list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry)
list_del(&cbq->callback_entry);
Expand Down
47 changes: 12 additions & 35 deletions drivers/connector/connector.c
View file
Expand Up @@ -122,51 +122,28 @@ EXPORT_SYMBOL_GPL(cn_netlink_send);
*/
static int cn_call_callback(struct sk_buff *skb)
{
struct cn_callback_entry *__cbq, *__new_cbq;
struct cn_callback_entry *i, *cbq = NULL;
struct cn_dev *dev = &cdev;
struct cn_msg *msg = NLMSG_DATA(nlmsg_hdr(skb));
struct netlink_skb_parms *nsp = &NETLINK_CB(skb);
int err = -ENODEV;

spin_lock_bh(&dev->cbdev->queue_lock);
list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
if (likely(!work_pending(&__cbq->work) &&
__cbq->data.skb == NULL)) {
__cbq->data.skb = skb;

if (queue_work(dev->cbdev->cn_queue,
&__cbq->work))
err = 0;
else
err = -EINVAL;
} else {
struct cn_callback_data *d;

err = -ENOMEM;
__new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
if (__new_cbq) {
d = &__new_cbq->data;
d->skb = skb;
d->callback = __cbq->data.callback;
d->free = __new_cbq;

INIT_WORK(&__new_cbq->work,
&cn_queue_wrapper);

if (queue_work(dev->cbdev->cn_queue,
&__new_cbq->work))
err = 0;
else {
kfree(__new_cbq);
err = -EINVAL;
}
}
}
list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
if (cn_cb_equal(&i->id.id, &msg->id)) {
atomic_inc(&i->refcnt);
cbq = i;
break;
}
}
spin_unlock_bh(&dev->cbdev->queue_lock);

if (cbq != NULL) {
cbq->callback(msg, nsp);
kfree_skb(skb);
cn_queue_release_callback(cbq);
}

return err;
}

Expand Down
16 changes: 3 additions & 13 deletions include/linux/connector.h
View file
Expand Up @@ -88,8 +88,6 @@ struct cn_queue_dev {
atomic_t refcnt;
unsigned char name[CN_CBQ_NAMELEN];

struct workqueue_struct *cn_queue;

struct list_head queue_list;
spinlock_t queue_lock;

Expand All @@ -101,20 +99,13 @@ struct cn_callback_id {
struct cb_id id;
};

struct cn_callback_data {
struct sk_buff *skb;
void (*callback) (struct cn_msg *, struct netlink_skb_parms *);

void *free;
};

struct cn_callback_entry {
struct list_head callback_entry;
struct work_struct work;
atomic_t refcnt;
struct cn_queue_dev *pdev;

struct cn_callback_id id;
struct cn_callback_data data;
void (*callback) (struct cn_msg *, struct netlink_skb_parms *);

u32 seq, group;
};
Expand All @@ -138,13 +129,12 @@ int cn_queue_add_callback(struct cn_queue_dev *dev, const char *name,
struct cb_id *id,
void (*callback)(struct cn_msg *, struct netlink_skb_parms *));
void cn_queue_del_callback(struct cn_queue_dev *dev, struct cb_id *id);
void cn_queue_release_callback(struct cn_callback_entry *);

struct cn_queue_dev *cn_queue_alloc_dev(const char *name, struct sock *);
void cn_queue_free_dev(struct cn_queue_dev *dev);

int cn_cb_equal(struct cb_id *, struct cb_id *);

void cn_queue_wrapper(struct work_struct *work);

#endif /* __KERNEL__ */
#endif /* __CONNECTOR_H */

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