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[184.163.105.249]) by smtp.gmail.com with ESMTPSA id w34sm19578545qtj.27.2019.02.05.08.35.29 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 05 Feb 2019 08:35:29 -0800 (PST) Date: Tue, 5 Feb 2019 11:35:28 -0500 Message-ID: <20190205113528.GD13620@t480s.localdomain> From: Vivien Didelot To: Marc Zyngier Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Lunn , Florian Fainelli , "David S. Miller" Subject: Re: [PATCH] net: dsa: Fix lockdep false positive splat In-Reply-To: <20190202175329.5969-1-marc.zyngier@arm.com> References: <20190202175329.5969-1-marc.zyngier@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, 2 Feb 2019 17:53:29 +0000, Marc Zyngier wrote: > Creating a macvtap on a DSA-backed interface results in the following > splat when lockdep is enabled: > > [ 19.638080] IPv6: ADDRCONF(NETDEV_CHANGE): lan0: link becomes ready > [ 23.041198] device lan0 entered promiscuous mode > [ 23.043445] device eth0 entered promiscuous mode > [ 23.049255] > [ 23.049557] ============================================ > [ 23.055021] WARNING: possible recursive locking detected > [ 23.060490] 5.0.0-rc3-00013-g56c857a1b8d3 #118 Not tainted > [ 23.066132] -------------------------------------------- > [ 23.071598] ip/2861 is trying to acquire lock: > [ 23.076171] 00000000f61990cb (_xmit_ETHER){+...}, at: dev_set_rx_mode+0x1c/0x38 > [ 23.083693] > [ 23.083693] but task is already holding lock: > [ 23.089696] 00000000ecf0c3b4 (_xmit_ETHER){+...}, at: dev_uc_add+0x24/0x70 > [ 23.096774] > [ 23.096774] other info that might help us debug this: > [ 23.103494] Possible unsafe locking scenario: > [ 23.103494] > [ 23.109584] CPU0 > [ 23.112093] ---- > [ 23.114601] lock(_xmit_ETHER); > [ 23.117917] lock(_xmit_ETHER); > [ 23.121233] > [ 23.121233] *** DEADLOCK *** > [ 23.121233] > [ 23.127325] May be due to missing lock nesting notation > [ 23.127325] > [ 23.134315] 2 locks held by ip/2861: > [ 23.137987] #0: 000000003b766c72 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x338/0x4e0 > [ 23.146231] #1: 00000000ecf0c3b4 (_xmit_ETHER){+...}, at: dev_uc_add+0x24/0x70 > [ 23.153757] > [ 23.153757] stack backtrace: > [ 23.158243] CPU: 0 PID: 2861 Comm: ip Not tainted 5.0.0-rc3-00013-g56c857a1b8d3 #118 > [ 23.166212] Hardware name: Globalscale Marvell ESPRESSOBin Board (DT) > [ 23.172843] Call trace: > [ 23.175358] dump_backtrace+0x0/0x188 > [ 23.179116] show_stack+0x14/0x20 > [ 23.182524] dump_stack+0xb4/0xec > [ 23.185928] __lock_acquire+0x123c/0x1860 > [ 23.190048] lock_acquire+0xc8/0x248 > [ 23.193724] _raw_spin_lock_bh+0x40/0x58 > [ 23.197755] dev_set_rx_mode+0x1c/0x38 > [ 23.201607] dev_set_promiscuity+0x3c/0x50 > [ 23.205820] dsa_slave_change_rx_flags+0x5c/0x70 > [ 23.210567] __dev_set_promiscuity+0x148/0x1e0 > [ 23.215136] __dev_set_rx_mode+0x74/0x98 > [ 23.219167] dev_uc_add+0x54/0x70 > [ 23.222575] macvlan_open+0x170/0x1d0 > [ 23.226336] __dev_open+0xe0/0x160 > [ 23.229830] __dev_change_flags+0x16c/0x1b8 > [ 23.234132] dev_change_flags+0x20/0x60 > [ 23.238074] do_setlink+0x2d0/0xc50 > [ 23.241658] __rtnl_newlink+0x5f8/0x6e8 > [ 23.245601] rtnl_newlink+0x50/0x78 > [ 23.249184] rtnetlink_rcv_msg+0x360/0x4e0 > [ 23.253397] netlink_rcv_skb+0xe8/0x130 > [ 23.257338] rtnetlink_rcv+0x14/0x20 > [ 23.261012] netlink_unicast+0x190/0x210 > [ 23.265043] netlink_sendmsg+0x288/0x350 > [ 23.269075] sock_sendmsg+0x18/0x30 > [ 23.272659] ___sys_sendmsg+0x29c/0x2c8 > [ 23.276602] __sys_sendmsg+0x60/0xb8 > [ 23.280276] __arm64_sys_sendmsg+0x1c/0x28 > [ 23.284488] el0_svc_common+0xd8/0x138 > [ 23.288340] el0_svc_handler+0x24/0x80 > [ 23.292192] el0_svc+0x8/0xc > > This looks fairly harmless (no actual deadlock occurs), and is > fixed in a similar way to c6894dec8ea9 ("bridge: fix lockdep > addr_list_lock false positive splat") by putting the addr_list_lock > in its own lockdep class. > > Signed-off-by: Marc Zyngier Reviewed-by: Vivien Didelot