netdev - Re: Latest net-next from GIT panic

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Message-ID: <1505918451.29839.97.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Wed, 20 Sep 2017 07:40:51 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Paweł Staszewski <pstaszewski@...are.pl>
Cc:     Wei Wang <weiwan@...gle.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        edumazet@...gle.com
Subject: Re: Latest net-next from GIT panic

On Wed, 2017-09-20 at 16:03 +0200, Paweł Staszewski wrote:
> Nit much more after adding this patch
> 
> https://bugzilla.kernel.org/attachment.cgi?id=258529
> 

This is why I suggested to replace the BUG() in another mail

So :

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f535779d9dc1dfe36934c2abba4e43d053ac5d6f..220cd12456754876edf2d3ef13195e82d70d5c74 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3331,7 +3331,15 @@ void netdev_run_todo(void);
  */
 static inline void dev_put(struct net_device *dev)
 {
-	this_cpu_dec(*dev->pcpu_refcnt);
+	int __percpu *pref = READ_ONCE(dev->pcpu_refcnt);
+
+	if (!pref) {
+		pr_err("no pcpu_refcnt on dev %p(%s) state %d dismantle %d\n",
+		       dev, dev->name, dev->reg_state, dev->dismantle);
+		for (;;)
+			cpu_relax();
+	}
+	this_cpu_dec(*pref);
 }
 
 /**