From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Fw: unregister_netdevice(): negative refcnt, suggest patch against 2.6.11 Date: Sun, 10 Apr 2005 03:44:46 -0700 Message-ID: <20050410034446.39e3025e.akpm@osdl.org> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="Multipart=_Sun__10_Apr_2005_03_44_46_-0700_Adc8qDJbGBrDBpST" Cc: Felix Palmen Return-path: To: netdev@oss.sgi.com Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org This is a multi-part message in MIME format. --Multipart=_Sun__10_Apr_2005_03_44_46_-0700_Adc8qDJbGBrDBpST Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit That sounds like a bug in appletalk or in the tap driver. Please describe a means by which other developers can reproduce that bug (a sequence of shell commands would be ideal). Thanks. Begin forwarded message: Date: Sun, 10 Apr 2005 11:16:25 +0200 From: Felix Palmen To: linux-kernel@vger.kernel.org Subject: unregister_netdevice(): negative refcnt, suggest patch against 2.6.11 Hi lkml-members, I recently had a problem with appletalk. After starting atalkd on a TAP interface and stopping it later, unregister_netdevice() just stated | unregister_netdevice: waiting for tap0 to become free. Usage count = -1 So I assume there is a problem in the appletalk code, but I didn't try reproducing that on other systems so far. I changed my kernel to "correct" a negative refcnt to 0 and that kind of fixes the problem. I'm not sure whether this could break anything, but certainly waiting for a device to become free is no use when there is a negative number of users, so I think it would be better to allow the system to shut down cleanly in this case. Here's m suggestion: #v+ --- linux-2.6.11-orig/net/core/dev.c 2005-03-02 08:38:09.000000000 +0100 +++ linux-2.6.11/net/core/dev.c 2005-04-09 16:44:42.000000000 +0200 @@ -2876,7 +2876,7 @@ unsigned long rebroadcast_time, warning_time; rebroadcast_time = warning_time = jiffies; - while (atomic_read(&dev->refcnt) != 0) { + while (atomic_read(&dev->refcnt) > 0) { if (time_after(jiffies, rebroadcast_time + 1 * HZ)) { rtnl_shlock(); @@ -2910,6 +2910,13 @@ warning_time = jiffies; } } + if (atomic_read(&dev->refcnt) != 0) { + printk(KERN_ERR "unregister_netdevice: " + "%s has negative refcnt (%d). " + "This should never happen! Setting refcnt to 0.\n", + dev->name, atomic_read(&dev->refcnt)); + atomic_set(&dev->refcnt, 0); + } } /* The sequence is: #v- Greets, Felix PS: Please note I'm not subscribed to lkml and CC me in replies, thanks. -- | /"\ ASCII Ribbon | Felix M. Palmen (Zirias) http://zirias.ath.cx/ | | \ / Campaign Against | fmp@palmen.homeip.net encrypted mail welcome | | X HTML In Mail | PGP key: http://zirias.ath.cx/pub.txt | | / \ And News | ED9B 62D0 BE39 32F9 2488 5D0C 8177 9D80 5ECF F683 | --Multipart=_Sun__10_Apr_2005_03_44_46_-0700_Adc8qDJbGBrDBpST Content-Type: application/pgp-signature; name="signature.asc" Content-Disposition: attachment; filename="signature.asc" Content-Transfer-Encoding: base64 LS0tLS1CRUdJTiBQR1AgU0lHTkFUVVJFLS0tLS0KVmVyc2lvbjogR251UEcgdjEuMi41IChHTlUv TGludXgpCgppUUNWQXdVQlFsanU2UVNxKzNneEc5Y05BUUpHV1FQOENnSFA3NFJCRDdEQldTLzhE MXV2U2JrOFUyaEY1TmM5CkUrQmdUT2NGYjM0NVlDVnFTUHluajBjT1IxSVNMMmVTWTdOWERKanBE QXhGbkY1U1kvY091bGdxRkozTEhXSjQKa2l2azh1eXNUc1ZhZ2pGandUSmQ2ejRyRnhJd1IwVjR0 UmpGYk4wQkxhR3RPc2Z3T2Jqd0tkdk82WVQydEJVNwpGc0J3Tm5raWZDWT0KPUZPbU0KLS0tLS1F TkQgUEdQIFNJR05BVFVSRS0tLS0tCgo= --Multipart=_Sun__10_Apr_2005_03_44_46_-0700_Adc8qDJbGBrDBpST--