linux-kernel - Re: [Linux 4.2-rc8+...v4.3-rc2] REGRESSION: ppp: circular locking dependency detected: [pppd] ppp_dev_uninit()

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Message-ID: <20150923103803.GC2869@alphalink.fr>
Date:	Wed, 23 Sep 2015 12:38:03 +0200
From:	Guillaume Nault <g.nault@...halink.fr>
To:	Sedat Dilek <sedat.dilek@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Linux 4.2-rc8+...v4.3-rc2] REGRESSION: ppp: circular locking
 dependency detected: [pppd] ppp_dev_uninit() | rtnl_lock()

On Wed, Sep 23, 2015 at 08:06:16AM +0200, Sedat Dilek wrote:
> Without reverting the below culprit ppp patch...
> 
> commit/?id=8cb775bc0a34dc596837e7da03fd22c747be618b
> ("ppp: fix device unregistration upon netns deletion")
> 
> ...I have an unstable Internet connection via Network-Manager/ModemManager.
> 
> First I saw this with Linux v4.2.
> 

Thanks for reporting the issue. Can you test this patch ?

---
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 0481daf..ed00446 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -2755,6 +2755,7 @@ static struct ppp *ppp_create_interface(struct net *net, int unit,
 	 */
 	dev_net_set(dev, net);
 
+	rtnl_lock();
 	mutex_lock(&pn->all_ppp_mutex);
 
 	if (unit < 0) {
@@ -2785,7 +2786,7 @@ static struct ppp *ppp_create_interface(struct net *net, int unit,
 	ppp->file.index = unit;
 	sprintf(dev->name, "ppp%d", unit);
 
-	ret = register_netdev(dev);
+	ret = register_netdevice(dev);
 	if (ret != 0) {
 		unit_put(&pn->units_idr, unit);
 		netdev_err(ppp->dev, "PPP: couldn't register device %s (%d)\n",
@@ -2797,6 +2798,7 @@ static struct ppp *ppp_create_interface(struct net *net, int unit,
 
 	atomic_inc(&ppp_unit_count);
 	mutex_unlock(&pn->all_ppp_mutex);
+	rtnl_unlock();
 
 	*retp = 0;
 	return ppp;
--
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