• K. Y. Srinivasan's avatar
    Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read() · a389fcfd
    K. Y. Srinivasan authored
    On the consumer side, we have interrupt driven flow management of the
    producer. It is sufficient to base the signaling decision on the
    amount of space that is available to write after the read is complete.
    The current code samples the previous available space and uses this
    in making the signaling decision. This state can be stale and is
    unnecessary. Since the state can be stale, we end up not signaling
    the host (when we should) and this can result in a hang. Fix this
    problem by removing the unnecessary check. I would like to thank
    Arseney Romanenko <arseneyr@microsoft.com> for pointing out this issue.
    
    Also, issue a full memory barrier before making the signaling descision
    to correctly deal with potential reordering of the write (read index)
    followed by the read of pending_sz.
    Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
    Tested-by: default avatarDexuan Cui <decui@microsoft.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    a389fcfd
ring_buffer.c 12.5 KB