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    Subject[patch 07/22] sparc64: Kill spurious NMI watchdog triggers by increasing limit to 30 seconds.
    2.6.30-stable review patch.  If anyone has any objections, please let us know.

    From: David S. Miller <>

    [ Upstream commit e6617c6ec28a17cf2f90262b835ec05b9b861400 ]

    This is a compromise and a temporary workaround for bootup NMI
    watchdog triggers some people see with qla2xxx devices present.

    This happens when, for example:

    CPU 0 is in the driver init and looping submitting mailbox commands to
    load the firmware, then waiting for completion.

    CPU 1 is receiving the device interrupts. CPU 1 is where the NMI
    watchdog triggers.

    CPU 0 is submitting mailbox commands fast enough that by the time CPU
    1 returns from the device interrupt handler, a new one is pending.
    This sequence runs for more than 5 seconds.

    The problematic case is CPU 1's timer interrupt running when the
    barrage of device interrupts begin. Then we have:

    timer interrupt
    return for softirq checking
    pending, thus enable interrupts

    qla2xxx interrupt
    qla2xxx interrupt
    ... 5+ seconds pass
    final qla2xxx interrupt for fw load

    run timer softirq

    At some point in the multi-second qla2xxx interrupt storm we trigger
    the NMI watchdog on CPU 1 from the NMI interrupt handler.

    The timer softirq, once we get back to running it, is smart enough to
    run the timer work enough times to make up for the missed timer

    However, the NMI watchdogs (both x86 and sparc) use the timer
    interrupt count to notice the cpu is wedged. But in the above
    scenerio we'll receive only one such timer interrupt even if we last
    all the way back to running the timer softirq.

    The default watchdog trigger point is only 5 seconds, which is pretty
    low (the softwatchdog triggers at 60 seconds). So increase it to 30
    seconds for now.

    Signed-off-by: David S. Miller <>
    Signed-off-by: Greg Kroah-Hartman <>
    arch/sparc/kernel/nmi.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/arch/sparc/kernel/nmi.c
    +++ b/arch/sparc/kernel/nmi.c
    @@ -103,7 +103,7 @@ notrace __kprobes void perfctr_irq(int i
    if (!touched && __get_cpu_var(last_irq_sum) == sum) {
    - if (local_read(&__get_cpu_var(alert_counter)) == 5 * nmi_hz)
    + if (local_read(&__get_cpu_var(alert_counter)) == 30 * nmi_hz)
    die_nmi("BUG: NMI Watchdog detected LOCKUP",
    regs, panic_on_timeout);
    } else {

     \ /
      Last update: 2009-09-11 02:37    [W:0.023 / U:2.024 seconds]
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