lkml.org 
[lkml]   [2011]   [Mar]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] x86, UV: Fix NMI handler for UV platforms
    On Mon, Mar 21, 2011 at 08:19:09PM +0300, Cyrill Gorcunov wrote:
    > On 03/21/2011 08:08 PM, Jack Steiner wrote:
    > > On Mon, Mar 21, 2011 at 08:00:53PM +0300, Cyrill Gorcunov wrote:
    > >> On 03/21/2011 07:43 PM, Cyrill Gorcunov wrote:
    > >> ...
    > >>>
    > >>> I think Jack might need to setup priority for his notifier, like
    > >>>
    > >>> static struct notifier_block uv_dump_stack_nmi_nb = {
    > >>> .notifier_call = uv_handle_nmi,
    > >>> .priority = NMI_LOCAL_HIGH_PRIOR+1,
    > >>> };
    > >>>
    > >>> so it would be called before perf nmi. Don, am I right?
    > >>>
    > >>> Since for perf nmis we do have
    > >>>
    > >>> static __read_mostly struct notifier_block perf_event_nmi_notifier = {
    > >>> .notifier_call = perf_event_nmi_handler,
    > >>> .next = NULL,
    > >>> .priority = NMI_LOCAL_LOW_PRIOR,
    > >>> };
    > >>>
    > >>
    > >> I must admit I've missed the fact that Jack has tried NMIs priorities, right?
    > >> x86_platform_ops seems to be a cleaner indeed (btw I think p4 pmu kgdb issue
    > >> is exactly the same problem) but same time this might end up in over-swelled
    > >> ideas behind this small code snippet. Dunno. Probably we need some per-cpu
    > >> system status for nmi reasons other than unknown nmis...
    > >
    > > We use KDB internally, and yes, it has the same issue. The version of the
    > > patch that uses KDB OR's the "handled" status for both KDB & the UV NMI handler.
    > > If either KDB or the UV NMI handler returns "handled", the code in traps.c exits
    > > after the call to the first die notifier.
    > >
    > > Not particularily pretty but I could not find a better way to do it.
    > >
    > > --- jack
    >
    > Another option might be to add pre-nmi notifier chain, which of course
    > not much differ from platform ops but I guess platform ops stands mostly
    > for one-shot events while chain might be more flexible. Ie I mean something
    > like
    >
    > if (notify_pre_die(DIE_NMI, "nmi", regs, 0, 2, SIGINT) == NOTIFY_STOP)
    > return;

    You still need to process both chains in order to handle the case where both
    hw_perf & the SGI BMC raise NMIs at about the same time.

    --- jack


    \
     
     \ /
      Last update: 2011-03-21 18:37    [W:0.025 / U:94.492 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site