From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net v2] bridge: disable softirqs around br_fdb_update to avoid lockup Date: Sun, 07 Jun 2015 19:45:12 -0700 (PDT) Message-ID: <20150607.194512.2301839969251363199.davem@davemloft.net> References: <1433490777-22880-1-git-send-email-nikolay@cumulusnetworks.com> <1433598540-13814-1-git-send-email-nikolay@cumulusnetworks.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, wkok@cumulusnetworks.com, stephen@networkplumber.org To: nikolay@cumulusnetworks.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:49464 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751081AbbFHCpN (ORCPT ); Sun, 7 Jun 2015 22:45:13 -0400 In-Reply-To: <1433598540-13814-1-git-send-email-nikolay@cumulusnetworks.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Nikolay Aleksandrov Date: Sat, 6 Jun 2015 06:49:00 -0700 > br_fdb_update() can be called in process context in the following way: > br_fdb_add() -> __br_fdb_add() -> br_fdb_update() (if NTF_USE flag is set) > so we need to disable softirqs because there are softirq users of the > hash_lock. One easy way to reproduce this is to modify the bridge utility > to set NTF_USE, enable stp and then set maxageing to a low value so > br_fdb_cleanup() is called frequently and then just add new entries in > a loop. This happens because br_fdb_cleanup() is called from timer/softirq > context. The spin locks in br_fdb_update were _bh before commit f8ae737deea1 > ("[BRIDGE]: forwarding remove unneeded preempt and bh diasables") > and at the time that commit was correct because br_fdb_update() couldn't be > called from process context, but that changed after commit: > 292d1398983f ("bridge: add NTF_USE support") > Using local_bh_disable/enable around br_fdb_update() allows us to keep > using the spin_lock/unlock in br_fdb_update for the fast-path. > > Signed-off-by: Nikolay Aleksandrov > Fixes: 292d1398983f ("bridge: add NTF_USE support") > --- > v2: new patch, uses local_bh_disable/enable instead of _bh variant > of spinlocks to keep the fast-path optimization. Please drop > "bridge: use _bh spinlock variant for br_fdb_update to avoid lockup" > in favor of this one. Ok, I accidently applied v1, so I reverted that and applied and queued this one instead for -stable. Thanks.