IB/ipoib: Fix race between light events and interface restart
authorFeras Daoud <ferasda@mellanox.com>
Mon, 10 Jul 2017 15:45:41 +0000 (18:45 +0300)
committerLeon Romanovsky <leon@kernel.org>
Sun, 23 Jul 2017 06:45:11 +0000 (09:45 +0300)
commitedf3f301db7af7e784d06f7059dfc8a69359af13
tree6b6ea80e00ca4c68cd8571ccc6783575cc1499eb
parenta62ab66b13a0f9bcb17b7b761f6670941ed5cd62
IB/ipoib: Fix race between light events and interface restart

A potential race between light_event and interface restart
may attach multicast group to an already attached QP.

Scenario:
light_event flow goes through ipoib_mcast_dev_flush function,
if a context switch occurs before calling ipoib_mcast_remove_list,
then we may face a situation where the broadcast of the priv is null
and the corresponding QP is not detached yet.
If an "interface restart" runs during the previous context switch,
the following scenario occurs:
When the device goes up, ipoib_ib_dev_up function will be called,
it will send a new registration request to the broadcast group and then
attach the group to the QP that was not detached before.

     IPOIB_FLUSH_LIGHT                                          INTERFACE RESTART

    __ipoib_ib_dev_flush                                                |
        |                                                               |
        |                                                               |
        |                                                               |
    ipoib_mcast_dev_flush                                               |
    Move mcast list and broadcast to remove_list                        |
        |                                                               |
        |                                                               |
    Context Switch-->                                                   |
        |                                                       ipoib_ib_dev_down
        |                                                               |
        |                                                               |
        |                                                       ipoib_ib_dev_up
        |                                                               |
        |                                                               |
        |                                                       ipoib_mcast_join_task
        |                                                       allocate new broadcast
        |                                                               |
        |                                                               |
        |                                                       Attach QP to multicast group
        |                                                               |
        |                                                               |
        |                                                       <--Context Switch
    ipoib_mcast_leave
    Detach QP from multicast group

Signed-off-by: Feras Daoud <ferasda@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
drivers/infiniband/ulp/ipoib/ipoib.h
drivers/infiniband/ulp/ipoib/ipoib_main.c
drivers/infiniband/ulp/ipoib/ipoib_multicast.c