• Salil Mehta's avatar
    net: hns: Fix the stray netpoll locks causing deadlock in NAPI path · bf5a6b4c
    Salil Mehta authored
    This patch fixes the problem of the spin locks, originally
    meant for the netpoll path of hns driver, causing deadlock in
    the normal NAPI poll path. The issue happened due to the presence
    of the stray leftover spin lock code related to the netpoll,
    whose support was earlier removed from the HNS[1], got activated
    due to enabling of NET_POLL_CONTROLLER switch.
    
    Earlier background:
    The netpoll handling code originally had this bug(as identified
    by Marc Zyngier[2]) of wrong spin lock API being used which did
    not disable the interrupts and hence could cause locking issues.
    i.e. if the lock were first acquired in context to thread like
    'ip' util and this lock if ever got later acquired again in
    context to the interrupt context like TX/RX (Interrupts could
    always pre-empt the lock holding task and acquire the lock again)
    and hence could cause deadlock.
    
    Proposed Solution:
    1. If the netpoll was enabled in the HNS driver, which is not
       right now, we could have simply used spin_[un]lock_irqsave()
    2. But as netpoll is disabled, therefore, it is best to get rid
       of the existing locks and stray code for now. This should
       solve the problem reported by Marc.
    
    [1] https://git.kernel.org/torvalds/c/4bd2c03be7
    [2] https://patchwork.ozlabs.org/patch/1189139/
    
    Fixes: 4bd2c03b ("net: hns: remove ndo_poll_controller")
    Cc: lipeng <lipeng321@huawei.com>
    Cc: Yisen Zhuang <yisen.zhuang@huawei.com>
    Cc: Eric Dumazet <edumazet@google.com>
    Cc: David S. Miller <davem@davemloft.net>
    Reported-by: default avatarMarc Zyngier <maz@kernel.org>
    Acked-by: default avatarMarc Zyngier <maz@kernel.org>
    Tested-by: default avatarMarc Zyngier <maz@kernel.org>
    Signed-off-by: default avatarSalil Mehta <salil.mehta@huawei.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    bf5a6b4c
hnae.c 10.1 KB