From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.83 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794052070; b=xNu2E8fpLYrHqM+GMRPDdbZYLdcJyJqGm3MgkdIACjdqdNgegfzdEIMeVxTX+rrCwC2n CmlC9V2Fp9O3B48FDq8e2uJoHmWRV9ACZHwrq8AdnuNOZAwQz0kzG5XUAfHPUTO5NiMMM APPvujxoubES7+zE7RqtjOBFVYa94QCl43UglzBhoFbyMBNOVt0D5g9FNG02yQRBFmCvm 6WBU9nBzx0wa/eUp1pKtndqjvS5BuCALNnw8dcTfhqJmKgUpJjasLB7DzhKGnhtp5RHdb yWInyVPQZl3uNM+TVPzb7iRy4WR1k/9+W7BtzZwSCsoLu8MqUl8y34XJ3c76jxd5jbw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794052070; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:MIME-Version:Date:Content-Type: Content-Transfer-Encoding:From:Message-ID:TLS-Required:Subject:To:Cc: In-Reply-To:References; bh=GnHezEpsy7TwQxHl7QCtA4TWsPZS/fezs0Pa1IH2a4Q=; b=ADZ8SXqtXlQGUzvpD9qc+Het4CCZW2mZiTFddUnJpUCznm7YVdV3eBZcNmbPnWujl5Zl XQ3g2lQ5xRfYMKx45CHLM/y5grIXbmPl/8ryUACk/TbpFBEdTbUupCvMm1jAIPOy76w27 8IYLa+WMeyrs16whspTNzzr56pSSxTydYW0nH0ORkmxJaQfQaI+Ub9xiOPzICMVfdlDTq D5LSco74jOYgQpszYHyzOqNVSI5HVs542/9Zcy1JW3LlHXvwpsYar0n+hZ8RfOH5WqHhP rHUtA/fMSwqXkW06hH5gZqIsU/cpkoQ6ty138xw8IvhoAGM1HAuI2DVOvRs9E4sN/lg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=p35pArLu; arc=none smtp.remote-ip=95.215.58.83 Received: from mta1.migadu.com (out-83.mta1.migadu.com [95.215.58.83]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17C98606A331 for ; Sat, 7 Nov 2026 11:47:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 17C98606A331 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=p35pArLu X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=Xagw4uV/cJ7unFmTqNMB0IDgo84IicTToPr/WXewfaI=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1794052066; v=1; x=1794656866; b=p35pArLuJ3P4B8gSCE7O0EMkeuGZkNORiT5GAkNt0vagOrGUXSVmb7QrboQIh4ZJtqs2Ggx/ /58ab1+yO73qJtqSeqO/wUR01zAl71tx964nL3IIBPRJZ3/f6J3fUfRbLXKUo13gz8XDNUMU+sH pJ9l5E6Wu71julLJeNPhs+WU= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 86d04180e8eba885; Sat, 07 Nov 2026 11:47:45 +0000 X-Mizu-Trace-ID: 86d04180e8eba885 X-Migadu-Flow: FLOW_OUT X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Date: Sat, 07 Nov 2026 11:47:45 +0000 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: "Zqiang" Message-ID: TLS-Required: No Subject: Re: [PATCH] neighbour: Move the netdev_put() out of RCU callback To: "Kuniyuki Iwashima" Cc: davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: References: <20261009091941.5837-1-qiang.zhang@linux.dev> >=20 >=20On Fri, Oct 9, 2026 at 2:19 AM Zqiang wrote: >=20 >=20>=20 >=20> For builts with CONFIG_NET_DEV_REFCNT_TRACKER=3Dy kernels, netdev_p= ut() > > records the caller's stack trace via ref_tracker_free() for debuggin= g > > reference leaks. however, the netdev_put() is within pneigh_destroy(= ) > > RCU callback, this recorded stack is uninformative, it does not reve= al > > which code path initiated the deletion. > >=20 >=20Have you seen pneigh double-free ? What motivates this change ? Firstly, Apologies for delayed reply. Actually, I didn't see any double-free happening, just wanted it to record a meaningful callstack which on release path. After all, if doubl= e-free really occurs, the callstack of the RCU callback execution path will not = be helpful. >=20 >=20>=20 >=20> This commit therefore move netdev_put() from the RCU callback into = the > > caller's process context, and replace call_rcu() with kfree_rcu(). > >=20 >=20> Fixes: d539d8fbd8fc ("neighbour: Free pneigh_entry after RCU grace= period.") > >=20 >=20Please elaborate why your change is safe in the commit message > and remove the tag. Does it refer to using kfree_rcu instead of call_rcu ensures safely ? Thanks Zqiang >=20 >=20>=20 >=20> Signed-off-by: Zqiang > >=20 >=20nit: full name >=20 >=20>=20 >=20> --- > > net/core/neighbour.c | 14 ++++---------- > > 1 file changed, 4 insertions(+), 10 deletions(-) > >=20 >=20> diff --git a/net/core/neighbour.c b/net/core/neighbour.c > > index 6ed8eb075146..4263689fc415 100644 > > --- a/net/core/neighbour.c > > +++ b/net/core/neighbour.c > > @@ -818,14 +818,6 @@ int pneigh_create(struct neigh_table *tbl, > > return err; > > } > >=20 >=20> -static void pneigh_destroy(struct rcu_head *rcu) > > -{ > > - struct pneigh_entry *n =3D container_of(rcu, struct pneigh_entry, = rcu); > > - > > - netdev_put(n->dev, &n->dev_tracker); > > - kfree(n); > > -} > > - > > int pneigh_delete(struct neigh_table *tbl, const void *pkey, > > struct net_device *dev) > > { > > @@ -849,7 +841,8 @@ int pneigh_delete(struct neigh_table *tbl, const= void *pkey, > > if (tbl->pdestructor) > > tbl->pdestructor(n); > >=20 >=20> - call_rcu(&n->rcu, pneigh_destroy); > > + netdev_put(n->dev, &n->dev_tracker); > > + kfree_rcu(n, rcu); > > return 0; > > } > > } > > @@ -891,7 +884,8 @@ static void pneigh_ifdown(struct neigh_table *tb= l, struct net_device *dev, > > if (tbl->pdestructor) > > tbl->pdestructor(n); > >=20 >=20> - call_rcu(&n->rcu, pneigh_destroy); > > + netdev_put(n->dev, &n->dev_tracker); > > + kfree_rcu(n, rcu); > > } > > } > >=20 >=20> -- > > 2.17.1 > > >