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Message-Id: <20210615003016.477-8-ryazanov.s.a@gmail.com>
Date: Tue, 15 Jun 2021 03:30:13 +0300
From: Sergey Ryazanov <ryazanov.s.a@...il.com>
To: Loic Poulain <loic.poulain@...aro.org>,
Johannes Berg <johannes@...solutions.net>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org
Subject: [PATCH net-next 07/10] wwan: core: no more hold netdev ops owning module
The WWAN netdev ops owner holding was used to protect from the
unexpected memory disappear. This approach causes a dependency cycle
(driver -> core -> driver) and effectively prevents a WWAN driver
unloading. E.g. WWAN hwsim could not be unloaded until all simulated
devices are removed:
~# modprobe wwan_hwsim devices=2
~# lsmod | grep wwan
wwan_hwsim 16384 2
wwan 20480 1 wwan_hwsim
~# rmmod wwan_hwsim
rmmod: ERROR: Module wwan_hwsim is in use
~# echo > /sys/kernel/debug/wwan_hwsim/hwsim0/destroy
~# echo > /sys/kernel/debug/wwan_hwsim/hwsim1/destroy
~# lsmod | grep wwan
wwan_hwsim 16384 0
wwan 20480 1 wwan_hwsim
~# rmmod wwan_hwsim
For a real device driver this will cause an inability to unload module
until a served device is physically detached.
Since the last commit we are removing all child netdev(s) when a driver
unregister the netdev ops. This allows us to permit the driver
unloading, since any sane driver will call ops unregistering on a device
deinitialization. So, remove the holding of an ops owner to make it
easier to unload a driver module. The owner field has also beed removed
from the ops structure as there are no more users of this field.
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@...il.com>
---
drivers/net/mhi/net.c | 1 -
drivers/net/wwan/wwan_core.c | 10 ----------
drivers/net/wwan/wwan_hwsim.c | 1 -
include/linux/wwan.h | 2 --
4 files changed, 14 deletions(-)
diff --git a/drivers/net/mhi/net.c b/drivers/net/mhi/net.c
index 64af1e518484..ebd1dbf0a536 100644
--- a/drivers/net/mhi/net.c
+++ b/drivers/net/mhi/net.c
@@ -383,7 +383,6 @@ static void mhi_net_dellink(void *ctxt, struct net_device *ndev,
}
const struct wwan_ops mhi_wwan_ops = {
- .owner = THIS_MODULE,
.priv_size = sizeof(struct mhi_net_dev),
.setup = mhi_net_setup,
.newlink = mhi_net_newlink,
diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
index 3f04e674cdaa..28590405172c 100644
--- a/drivers/net/wwan/wwan_core.c
+++ b/drivers/net/wwan/wwan_core.c
@@ -921,11 +921,6 @@ int wwan_register_ops(struct device *parent, const struct wwan_ops *ops,
return -EBUSY;
}
- if (!try_module_get(ops->owner)) {
- wwan_remove_dev(wwandev);
- return -ENODEV;
- }
-
wwandev->ops = ops;
wwandev->ops_ctxt = ctxt;
@@ -952,7 +947,6 @@ static int wwan_child_dellink(struct device *dev, void *data)
void wwan_unregister_ops(struct device *parent)
{
struct wwan_device *wwandev = wwan_dev_get_by_parent(parent);
- struct module *owner;
LIST_HEAD(kill_list);
if (WARN_ON(IS_ERR(wwandev)))
@@ -968,8 +962,6 @@ void wwan_unregister_ops(struct device *parent)
*/
put_device(&wwandev->dev);
- owner = wwandev->ops->owner; /* Preserve ops owner */
-
rtnl_lock(); /* Prevent concurent netdev(s) creation/destroying */
/* Remove all child netdev(s), using batch removing */
@@ -981,8 +973,6 @@ void wwan_unregister_ops(struct device *parent)
rtnl_unlock();
- module_put(owner);
-
wwandev->ops_ctxt = NULL;
wwan_remove_dev(wwandev);
}
diff --git a/drivers/net/wwan/wwan_hwsim.c b/drivers/net/wwan/wwan_hwsim.c
index c1e850b9c087..a8582a58a385 100644
--- a/drivers/net/wwan/wwan_hwsim.c
+++ b/drivers/net/wwan/wwan_hwsim.c
@@ -94,7 +94,6 @@ static void wwan_hwsim_netdev_setup(struct net_device *ndev)
}
static const struct wwan_ops wwan_hwsim_wwan_rtnl_ops = {
- .owner = THIS_MODULE,
.priv_size = 0, /* No private data */
.setup = wwan_hwsim_netdev_setup,
};
diff --git a/include/linux/wwan.h b/include/linux/wwan.h
index 430a3a0817de..656a571b52ed 100644
--- a/include/linux/wwan.h
+++ b/include/linux/wwan.h
@@ -119,14 +119,12 @@ void *wwan_port_get_drvdata(struct wwan_port *port);
/**
* struct wwan_ops - WWAN device ops
- * @owner: module owner of the WWAN ops
* @priv_size: size of private netdev data area
* @setup: set up a new netdev
* @newlink: register the new netdev
* @dellink: remove the given netdev
*/
struct wwan_ops {
- struct module *owner;
unsigned int priv_size;
void (*setup)(struct net_device *dev);
int (*newlink)(void *ctxt, struct net_device *dev,
--
2.26.3
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