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    Subject[PATCH 4.19 001/219] af_packet: set defaule value for tmo
    Date
    From: Mao Wenan <maowenan@huawei.com>

    [ Upstream commit b43d1f9f7067c6759b1051e8ecb84e82cef569fe ]

    There is softlockup when using TPACKET_V3:
    ...
    NMI watchdog: BUG: soft lockup - CPU#2 stuck for 60010ms!
    (__irq_svc) from [<c0558a0c>] (_raw_spin_unlock_irqrestore+0x44/0x54)
    (_raw_spin_unlock_irqrestore) from [<c027b7e8>] (mod_timer+0x210/0x25c)
    (mod_timer) from [<c0549c30>]
    (prb_retire_rx_blk_timer_expired+0x68/0x11c)
    (prb_retire_rx_blk_timer_expired) from [<c027a7ac>]
    (call_timer_fn+0x90/0x17c)
    (call_timer_fn) from [<c027ab6c>] (run_timer_softirq+0x2d4/0x2fc)
    (run_timer_softirq) from [<c021eaf4>] (__do_softirq+0x218/0x318)
    (__do_softirq) from [<c021eea0>] (irq_exit+0x88/0xac)
    (irq_exit) from [<c0240130>] (msa_irq_exit+0x11c/0x1d4)
    (msa_irq_exit) from [<c0209cf0>] (handle_IPI+0x650/0x7f4)
    (handle_IPI) from [<c02015bc>] (gic_handle_irq+0x108/0x118)
    (gic_handle_irq) from [<c0558ee4>] (__irq_usr+0x44/0x5c)
    ...

    If __ethtool_get_link_ksettings() is failed in
    prb_calc_retire_blk_tmo(), msec and tmo will be zero, so tov_in_jiffies
    is zero and the timer expire for retire_blk_timer is turn to
    mod_timer(&pkc->retire_blk_timer, jiffies + 0),
    which will trigger cpu usage of softirq is 100%.

    Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.")
    Tested-by: Xiao Jiangfeng <xiaojiangfeng@huawei.com>
    Signed-off-by: Mao Wenan <maowenan@huawei.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/packet/af_packet.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/net/packet/af_packet.c
    +++ b/net/packet/af_packet.c
    @@ -552,7 +552,8 @@ static int prb_calc_retire_blk_tmo(struc
    msec = 1;
    div = ecmd.base.speed / 1000;
    }
    - }
    + } else
    + return DEFAULT_PRB_RETIRE_TOV;

    mbits = (blk_size_in_bytes * 8) / (1024 * 1024);


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