lkml.org 
[lkml]   [2015]   [Jul]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.13.y-ckt 49/56] bridge: disable softirqs around br_fdb_update to avoid lockup
    Date
    3.13.11-ckt23 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>

    commit c4c832f89dc468cf11dc0dd17206bace44526651 upstream.

    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 <nikolay@cumulusnetworks.com>
    Fixes: 292d1398983f ("bridge: add NTF_USE support")
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    net/bridge/br_fdb.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
    index 33e8f23..62c444d 100644
    --- a/net/bridge/br_fdb.c
    +++ b/net/bridge/br_fdb.c
    @@ -664,9 +664,11 @@ static int __br_fdb_add(struct ndmsg *ndm, struct net_bridge_port *p,
    int err = 0;

    if (ndm->ndm_flags & NTF_USE) {
    + local_bh_disable();
    rcu_read_lock();
    br_fdb_update(p->br, p, addr, vid);
    rcu_read_unlock();
    + local_bh_enable();
    } else {
    spin_lock_bh(&p->br->hash_lock);
    err = fdb_add_entry(p, addr, ndm->ndm_state,
    --
    1.9.1


    \
     
     \ /
      Last update: 2015-07-08 18:02    [W:4.086 / U:0.268 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site