linux-kernel - [RFC PATCH 17/30] isdn: Prepare isdn_net_get_locked

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Date:   Thu, 11 Oct 2018 01:12:04 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "David S . Miller" <davem@...emloft.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>
Subject: [RFC PATCH 17/30] isdn: Prepare isdn_net_get_locked_lp() for handling softirq mask

This function is implemented on top of spin_lock_bh() that is going to
handle a softirq mask in order to apply finegrained vector disablement.
The lock function is going to return the previous vectors enabled mask
prior to the last call to local_bh_disable(), following a similar model
to that of local_irq_save/restore. Subsequent calls to local_bh_disable()
and friends can then stack up:

	bh = local_bh_disable(vec_mask);
		isdn_net_get_locked_lp(&bh2) {
			spin_lock(...)
			*bh2 = local_bh_disable(...)
		}
		...
		spin_unlock_bh(bh2, ...);
	local_bh_enable(bh);

To prepare for that, make isdn_net_get_locked_lp() able to return a
saved vector enabled mask. We'll plug it to spin_[un]lock_bh() in a
subsequent patch.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: David S. Miller <davem@...emloft.net>
Cc: Mauro Carvalho Chehab <mchehab@...pensource.com>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 drivers/isdn/i4l/isdn_concap.c | 3 ++-
 drivers/isdn/i4l/isdn_net.c    | 3 ++-
 drivers/isdn/i4l/isdn_net.h    | 3 ++-
 drivers/isdn/i4l/isdn_ppp.c    | 3 ++-
 4 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/isdn/i4l/isdn_concap.c b/drivers/isdn/i4l/isdn_concap.c
index 336523e..4352bec 100644
--- a/drivers/isdn/i4l/isdn_concap.c
+++ b/drivers/isdn/i4l/isdn_concap.c
@@ -41,9 +41,10 @@
 
 static int isdn_concap_dl_data_req(struct concap_proto *concap, struct sk_buff *skb)
 {
+	unsigned int bh;
 	struct net_device *ndev = concap->net_dev;
 	isdn_net_dev *nd = ((isdn_net_local *) netdev_priv(ndev))->netdev;
-	isdn_net_local *lp = isdn_net_get_locked_lp(nd);
+	isdn_net_local *lp = isdn_net_get_locked_lp(nd, &bh);
 
 	IX25DEBUG("isdn_concap_dl_data_req: %s \n", concap->net_dev->name);
 	if (!lp) {
diff --git a/drivers/isdn/i4l/isdn_net.c b/drivers/isdn/i4l/isdn_net.c
index c138f66..a9687ca 100644
--- a/drivers/isdn/i4l/isdn_net.c
+++ b/drivers/isdn/i4l/isdn_net.c
@@ -1054,6 +1054,7 @@ isdn_net_xmit(struct net_device *ndev, struct sk_buff *skb)
 	isdn_net_local *slp;
 	isdn_net_local *lp = netdev_priv(ndev);
 	int retv = NETDEV_TX_OK;
+	unsigned int bh;
 
 	if (((isdn_net_local *) netdev_priv(ndev))->master) {
 		printk("isdn BUG at %s:%d!\n", __FILE__, __LINE__);
@@ -1068,7 +1069,7 @@ isdn_net_xmit(struct net_device *ndev, struct sk_buff *skb)
 	}
 #endif
 	nd = ((isdn_net_local *) netdev_priv(ndev))->netdev;
-	lp = isdn_net_get_locked_lp(nd);
+	lp = isdn_net_get_locked_lp(nd, &bh);
 	if (!lp) {
 		printk(KERN_WARNING "%s: all channels busy - requeuing!\n", ndev->name);
 		return NETDEV_TX_BUSY;
diff --git a/drivers/isdn/i4l/isdn_net.h b/drivers/isdn/i4l/isdn_net.h
index cca6d68..f4621b1 100644
--- a/drivers/isdn/i4l/isdn_net.h
+++ b/drivers/isdn/i4l/isdn_net.h
@@ -76,7 +76,8 @@ static __inline__ int isdn_net_lp_busy(isdn_net_local *lp)
  * For the given net device, this will get a non-busy channel out of the
  * corresponding bundle. The returned channel is locked.
  */
-static __inline__ isdn_net_local *isdn_net_get_locked_lp(isdn_net_dev *nd)
+static __inline__ isdn_net_local *isdn_net_get_locked_lp(isdn_net_dev *nd,
+							 unsigned int *bh)
 {
 	unsigned long flags;
 	isdn_net_local *lp;
diff --git a/drivers/isdn/i4l/isdn_ppp.c b/drivers/isdn/i4l/isdn_ppp.c
index a7b275e..4c5ac13 100644
--- a/drivers/isdn/i4l/isdn_ppp.c
+++ b/drivers/isdn/i4l/isdn_ppp.c
@@ -1258,6 +1258,7 @@ isdn_ppp_xmit(struct sk_buff *skb, struct net_device *netdev)
 	unsigned int proto = PPP_IP;     /* 0x21 */
 	struct ippp_struct *ipt, *ipts;
 	int slot, retval = NETDEV_TX_OK;
+	unsigned int bh;
 
 	mlp = netdev_priv(netdev);
 	nd = mlp->netdev;       /* get master lp */
@@ -1292,7 +1293,7 @@ isdn_ppp_xmit(struct sk_buff *skb, struct net_device *netdev)
 		goto out;
 	}
 
-	lp = isdn_net_get_locked_lp(nd);
+	lp = isdn_net_get_locked_lp(nd, &bh);
 	if (!lp) {
 		printk(KERN_WARNING "%s: all channels busy - requeuing!\n", netdev->name);
 		retval = NETDEV_TX_BUSY;
-- 
2.7.4