From: Cong Wang <cwang@xxxxxxxxxxxxxxxx> Date: Mon, 6 Jan 2014 11:11:45 -0800 > On Mon, Jan 6, 2014 at 11:00 AM, Scott Feldman > <sfeldma@xxxxxxxxxxxxxxxxxxx> wrote: >> From: Curt Brune <curt@xxxxxxxxxxxxxxxxxxx> >> >> br_multicast_set_hash_max() is called from process context in >> net/bridge/br_sysfs_br.c by the sysfs store_hash_max() function. >> >> br_multicast_set_hash_max() calls spin_lock(&br->multicast_lock), >> which can deadlock the CPU if a softirq that also tries to take the >> same lock interrupts br_multicast_set_hash_max() while the lock is >> held . This can happen quite easily when any of the bridge multicast >> timers expire, which try to take the same lock. >> >> The fix here is to use spin_lock_bh(), preventing other softirqs from >> executing on this CPU. >> >> Steps to reproduce: >> >> 1. Create a bridge with several interfaces (I used 4). >> 2. Set the "multicast query interval" to a low number, like 2. >> 3. Enable the bridge as a multicast querier. >> 4. Repeatedly set the bridge hash_max parameter via sysfs. >> >> # brctl addbr br0 >> # brctl addif br0 eth1 eth2 eth3 eth4 >> # brctl setmcqi br0 2 >> # brctl setmcquerier br0 1 >> >> # while true ; do echo 4096 > /sys/class/net/br0/bridge/hash_max; done >> > > > I think this should probably go to net instead of net-next, > and -stable too. Agreed, applied to 'net' and queued up for -stable.
