Re: [PATCH net v2] net: lapb: Add locking to the lapb module
On Tue, Jan 19, 2021 at 3:34 AM Martin Schiller wrote: > > > 4. In lapb_device_event, replace the "lapb_disconnect_request" call > > with > > the content of "lapb_disconnect_request", to avoid trying to hold the > > lock twice. When I do this, I removed "lapb_start_t1timer" because I > > don't think it's necessary to start the timer when "NETDEV_GOING_DOWN". > > I don't like the code redundancy this creates. Maybe you should move the > actual functionality from lapb_disconnect_request() to a > __lapb_disconnect_request(), and in lapb_disconnect_request() call this > function including locking around it and also in lapb_device_event > (without locking). > > Calling lapb_start_t1timer() on a "NETDEV_GOING_DOWN" event does not > hurt and is correct from a protocol flow point of view after sending > the DISC. Thanks! I created a new __lapb_disconnect_request function and the code indeed looked cleaner. I'll send a new version.
Re: [PATCH net v2] net: lapb: Add locking to the lapb module
On 2021-01-17 23:47, Xie He wrote:
In the lapb module, the timers may run concurrently with other code in
this module, and there is currently no locking to prevent the code from
racing on "struct lapb_cb". This patch adds locking to prevent racing.
1. Add "spinlock_t lock" to "struct lapb_cb"; Add "spin_lock_bh" and
"spin_unlock_bh" to APIs, timer functions and notifier functions.
2. Add "bool t1timer_stop, t2timer_stop" to "struct lapb_cb" to make us
able to ask running timers to abort; Modify "lapb_stop_t1timer" and
"lapb_stop_t2timer" to make them able to abort running timers;
Modify "lapb_t2timer_expiry" and "lapb_t1timer_expiry" to make them
abort after they are stopped by "lapb_stop_t1timer",
"lapb_stop_t2timer",
and "lapb_start_t1timer", "lapb_start_t2timer".
3. In lapb_unregister, change "lapb_stop_t1timer" and
"lapb_stop_t2timer"
to "del_timer_sync" to make sure all running timers have exited.
4. In lapb_device_event, replace the "lapb_disconnect_request" call
with
the content of "lapb_disconnect_request", to avoid trying to hold the
lock twice. When I do this, I removed "lapb_start_t1timer" because I
don't think it's necessary to start the timer when "NETDEV_GOING_DOWN".
I don't like the code redundancy this creates. Maybe you should move the
actual functionality from lapb_disconnect_request() to a
__lapb_disconnect_request(), and in lapb_disconnect_request() call this
function including locking around it and also in lapb_device_event
(without locking).
Calling lapb_start_t1timer() on a "NETDEV_GOING_DOWN" event does not
hurt and is correct from a protocol flow point of view after sending
the DISC.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: Martin Schiller
Signed-off-by: Xie He
---
include/net/lapb.h| 2 ++
net/lapb/lapb_iface.c | 56 +++
net/lapb/lapb_timer.c | 30 +++
3 files changed, 80 insertions(+), 8 deletions(-)
diff --git a/include/net/lapb.h b/include/net/lapb.h
index ccc3d1f020b0..eee73442a1ba 100644
--- a/include/net/lapb.h
+++ b/include/net/lapb.h
@@ -92,6 +92,7 @@ struct lapb_cb {
unsigned short n2, n2count;
unsigned short t1, t2;
struct timer_list t1timer, t2timer;
+ boolt1timer_stop, t2timer_stop;
/* Internal control information */
struct sk_buff_head write_queue;
@@ -103,6 +104,7 @@ struct lapb_cb {
struct lapb_frame frmr_data;
unsigned char frmr_type;
+ spinlock_t lock;
refcount_t refcnt;
};
diff --git a/net/lapb/lapb_iface.c b/net/lapb/lapb_iface.c
index 40961889e9c0..45f332607685 100644
--- a/net/lapb/lapb_iface.c
+++ b/net/lapb/lapb_iface.c
@@ -122,6 +122,8 @@ static struct lapb_cb *lapb_create_cb(void)
timer_setup(>t1timer, NULL, 0);
timer_setup(>t2timer, NULL, 0);
+ lapb->t1timer_stop = true;
+ lapb->t2timer_stop = true;
lapb->t1 = LAPB_DEFAULT_T1;
lapb->t2 = LAPB_DEFAULT_T2;
@@ -129,6 +131,8 @@ static struct lapb_cb *lapb_create_cb(void)
lapb->mode= LAPB_DEFAULT_MODE;
lapb->window = LAPB_DEFAULT_WINDOW;
lapb->state = LAPB_STATE_0;
+
+ spin_lock_init(>lock);
refcount_set(>refcnt, 1);
out:
return lapb;
@@ -178,8 +182,8 @@ int lapb_unregister(struct net_device *dev)
goto out;
lapb_put(lapb);
- lapb_stop_t1timer(lapb);
- lapb_stop_t2timer(lapb);
+ del_timer_sync(>t1timer);
+ del_timer_sync(>t2timer);
lapb_clear_queues(lapb);
@@ -201,6 +205,8 @@ int lapb_getparms(struct net_device *dev, struct
lapb_parms_struct *parms)
if (!lapb)
goto out;
+ spin_lock_bh(>lock);
+
parms->t1 = lapb->t1 / HZ;
parms->t2 = lapb->t2 / HZ;
parms->n2 = lapb->n2;
@@ -219,6 +225,7 @@ int lapb_getparms(struct net_device *dev, struct
lapb_parms_struct *parms)
else
parms->t2timer = (lapb->t2timer.expires - jiffies) / HZ;
+ spin_unlock_bh(>lock);
lapb_put(lapb);
rc = LAPB_OK;
out:
@@ -234,6 +241,8 @@ int lapb_setparms(struct net_device *dev, struct
lapb_parms_struct *parms)
if (!lapb)
goto out;
+ spin_lock_bh(>lock);
+
rc = LAPB_INVALUE;
if (parms->t1 < 1 || parms->t2 < 1 || parms->n2 < 1)
goto out_put;
@@ -256,6 +265,7 @@ int lapb_setparms(struct net_device *dev, struct
lapb_parms_struct *parms)
rc = LAPB_OK;
out_put:
+ spin_unlock_bh(>lock);
lapb_put(lapb);
out:
return rc;
@@ -270,6 +280,8 @@ int lapb_connect_request(struct net_device *dev)
if (!lapb)
goto out;
+ spin_lock_bh(>lock);
+
rc = LAPB_OK;
if (lapb->state == LAPB_STATE_1)
goto out_put;
@@ -285,6 +297,7 @@ int lapb_connect_request(struct net_device *dev)
[PATCH net v2] net: lapb: Add locking to the lapb module
In the lapb module, the timers may run concurrently with other code in
this module, and there is currently no locking to prevent the code from
racing on "struct lapb_cb". This patch adds locking to prevent racing.
1. Add "spinlock_t lock" to "struct lapb_cb"; Add "spin_lock_bh" and
"spin_unlock_bh" to APIs, timer functions and notifier functions.
2. Add "bool t1timer_stop, t2timer_stop" to "struct lapb_cb" to make us
able to ask running timers to abort; Modify "lapb_stop_t1timer" and
"lapb_stop_t2timer" to make them able to abort running timers;
Modify "lapb_t2timer_expiry" and "lapb_t1timer_expiry" to make them
abort after they are stopped by "lapb_stop_t1timer", "lapb_stop_t2timer",
and "lapb_start_t1timer", "lapb_start_t2timer".
3. In lapb_unregister, change "lapb_stop_t1timer" and "lapb_stop_t2timer"
to "del_timer_sync" to make sure all running timers have exited.
4. In lapb_device_event, replace the "lapb_disconnect_request" call with
the content of "lapb_disconnect_request", to avoid trying to hold the
lock twice. When I do this, I removed "lapb_start_t1timer" because I
don't think it's necessary to start the timer when "NETDEV_GOING_DOWN".
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: Martin Schiller
Signed-off-by: Xie He
---
include/net/lapb.h| 2 ++
net/lapb/lapb_iface.c | 56 +++
net/lapb/lapb_timer.c | 30 +++
3 files changed, 80 insertions(+), 8 deletions(-)
diff --git a/include/net/lapb.h b/include/net/lapb.h
index ccc3d1f020b0..eee73442a1ba 100644
--- a/include/net/lapb.h
+++ b/include/net/lapb.h
@@ -92,6 +92,7 @@ struct lapb_cb {
unsigned short n2, n2count;
unsigned short t1, t2;
struct timer_list t1timer, t2timer;
+ boolt1timer_stop, t2timer_stop;
/* Internal control information */
struct sk_buff_head write_queue;
@@ -103,6 +104,7 @@ struct lapb_cb {
struct lapb_frame frmr_data;
unsigned char frmr_type;
+ spinlock_t lock;
refcount_t refcnt;
};
diff --git a/net/lapb/lapb_iface.c b/net/lapb/lapb_iface.c
index 40961889e9c0..45f332607685 100644
--- a/net/lapb/lapb_iface.c
+++ b/net/lapb/lapb_iface.c
@@ -122,6 +122,8 @@ static struct lapb_cb *lapb_create_cb(void)
timer_setup(>t1timer, NULL, 0);
timer_setup(>t2timer, NULL, 0);
+ lapb->t1timer_stop = true;
+ lapb->t2timer_stop = true;
lapb->t1 = LAPB_DEFAULT_T1;
lapb->t2 = LAPB_DEFAULT_T2;
@@ -129,6 +131,8 @@ static struct lapb_cb *lapb_create_cb(void)
lapb->mode= LAPB_DEFAULT_MODE;
lapb->window = LAPB_DEFAULT_WINDOW;
lapb->state = LAPB_STATE_0;
+
+ spin_lock_init(>lock);
refcount_set(>refcnt, 1);
out:
return lapb;
@@ -178,8 +182,8 @@ int lapb_unregister(struct net_device *dev)
goto out;
lapb_put(lapb);
- lapb_stop_t1timer(lapb);
- lapb_stop_t2timer(lapb);
+ del_timer_sync(>t1timer);
+ del_timer_sync(>t2timer);
lapb_clear_queues(lapb);
@@ -201,6 +205,8 @@ int lapb_getparms(struct net_device *dev, struct
lapb_parms_struct *parms)
if (!lapb)
goto out;
+ spin_lock_bh(>lock);
+
parms->t1 = lapb->t1 / HZ;
parms->t2 = lapb->t2 / HZ;
parms->n2 = lapb->n2;
@@ -219,6 +225,7 @@ int lapb_getparms(struct net_device *dev, struct
lapb_parms_struct *parms)
else
parms->t2timer = (lapb->t2timer.expires - jiffies) / HZ;
+ spin_unlock_bh(>lock);
lapb_put(lapb);
rc = LAPB_OK;
out:
@@ -234,6 +241,8 @@ int lapb_setparms(struct net_device *dev, struct
lapb_parms_struct *parms)
if (!lapb)
goto out;
+ spin_lock_bh(>lock);
+
rc = LAPB_INVALUE;
if (parms->t1 < 1 || parms->t2 < 1 || parms->n2 < 1)
goto out_put;
@@ -256,6 +265,7 @@ int lapb_setparms(struct net_device *dev, struct
lapb_parms_struct *parms)
rc = LAPB_OK;
out_put:
+ spin_unlock_bh(>lock);
lapb_put(lapb);
out:
return rc;
@@ -270,6 +280,8 @@ int lapb_connect_request(struct net_device *dev)
if (!lapb)
goto out;
+ spin_lock_bh(>lock);
+
rc = LAPB_OK;
if (lapb->state == LAPB_STATE_1)
goto out_put;
@@ -285,6 +297,7 @@ int lapb_connect_request(struct net_device *dev)
rc = LAPB_OK;
out_put:
+ spin_unlock_bh(>lock);
lapb_put(lapb);
out:
return rc;
@@ -299,6 +312,8 @@ int lapb_disconnect_request(struct net_device *dev)
if (!lapb)
goto out;
+ spin_lock_bh(>lock);
+
switch (lapb->state) {
case LAPB_STATE_0:
rc = LAPB_NOTCONNECTED;
@@ -330,6 +345,7 @@ int lapb_disconnect_request(struct net_device *dev)
rc = LAPB_OK;
out_put:
