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mac80211: add interface list lock

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Using only the RTNL has a number of problems, most notably that
ieee80211_iterate_active_interfaces() and other interface list
traversals cannot be done from the internal workqueue because it
needs to be flushed under the RTNL.

This patch introduces a new mutex that protects the interface list
against modifications. A more detailed explanation is part of the
code change.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Johannes Berg 2009-01-23 22:54:03 +01:00 committed by John W. Linville
parent 506d03f97d
commit c771c9d8da
5 changed files with 40 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/net/mac80211.h
View File

@ -928,9 +928,8 @@ enum ieee80211_hw_flags {
* @workqueue: single threaded workqueue available for driver use,
* allocated by mac80211 on registration and flushed when an
* interface is removed.
* NOTICE: All work performed on this workqueue should NEVER
* acquire the RTNL lock (i.e. Don't use the function
* ieee80211_iterate_active_interfaces())
* NOTICE: All work performed on this workqueue must not
* acquire the RTNL lock.
*
* @priv: pointer to private area that was allocated for driver use
* along with this structure.

2
net/mac80211/ieee80211_i.h
View File

@ -643,7 +643,9 @@ struct ieee80211_local {
struct crypto_blkcipher *wep_rx_tfm;
u32 wep_iv;
/* see iface.c */
struct list_head interfaces;
struct mutex iflist_mtx;
/*
* Key lock, protects sdata's key_list and sta_info's

31
net/mac80211/iface.c
View File

@ -21,6 +21,23 @@
#include "mesh.h"
#include "led.h"
/**
* DOC: Interface list locking
*
* The interface list in each struct ieee80211_local is protected
* three-fold:
*
* (1) modifications may only be done under the RTNL
* (2) modifications and readers are protected against each other by
* the iflist_mtx.
* (3) modifications are done in an RCU manner so atomic readers
* can traverse the list in RCU-safe blocks.
*
* As a consequence, reads (traversals) of the list can be protected
* by either the RTNL, the iflist_mtx or RCU.
*/
static int ieee80211_change_mtu(struct net_device *dev, int new_mtu)
{
int meshhdrlen;
@ -800,7 +817,9 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
params->mesh_id_len,
params->mesh_id);
mutex_lock(&local->iflist_mtx);
list_add_tail_rcu(&sdata->list, &local->interfaces);
mutex_unlock(&local->iflist_mtx);
if (new_dev)
*new_dev = ndev;
@ -816,7 +835,10 @@ void ieee80211_if_remove(struct ieee80211_sub_if_data *sdata)
{
ASSERT_RTNL();
mutex_lock(&sdata->local->iflist_mtx);
list_del_rcu(&sdata->list);
mutex_unlock(&sdata->local->iflist_mtx);
synchronize_rcu();
unregister_netdevice(sdata->dev);
}
@ -832,7 +854,16 @@ void ieee80211_remove_interfaces(struct ieee80211_local *local)
ASSERT_RTNL();
list_for_each_entry_safe(sdata, tmp, &local->interfaces, list) {
/*
* we cannot hold the iflist_mtx across unregister_netdevice,
* but we only need to hold it for list modifications to lock
* out readers since we're under the RTNL here as all other
* writers.
*/
mutex_lock(&local->iflist_mtx);
list_del(&sdata->list);
mutex_unlock(&local->iflist_mtx);
unregister_netdevice(sdata->dev);
}
}

3
net/mac80211/main.c
View File

@ -758,6 +758,7 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
local->hw.conf.radio_enabled = true;
INIT_LIST_HEAD(&local->interfaces);
mutex_init(&local->iflist_mtx);
spin_lock_init(&local->key_lock);
@ -1008,6 +1009,8 @@ void ieee80211_free_hw(struct ieee80211_hw *hw)
{
struct ieee80211_local *local = hw_to_local(hw);
mutex_destroy(&local->iflist_mtx);
wiphy_free(local->hw.wiphy);
}
EXPORT_SYMBOL(ieee80211_free_hw);

4
net/mac80211/util.c
View File

@ -468,7 +468,7 @@ void ieee80211_iterate_active_interfaces(
struct ieee80211_local *local = hw_to_local(hw);
struct ieee80211_sub_if_data *sdata;
rtnl_lock();
mutex_lock(&local->iflist_mtx);
list_for_each_entry(sdata, &local->interfaces, list) {
switch (sdata->vif.type) {
@ -489,7 +489,7 @@ void ieee80211_iterate_active_interfaces(
&sdata->vif);
}
rtnl_unlock();
mutex_unlock(&local->iflist_mtx);
}
EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces);