lkml.org 
[lkml]   [2010]   [Dec]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: perf hw in kexeced kernel broken in tip
    From
    Date
    On Wed, 2010-12-01 at 11:06 -0500, Vivek Goyal wrote:
    > On Wed, Dec 01, 2010 at 12:27:47PM +0100, Peter Zijlstra wrote:
    > > On Wed, 2010-12-01 at 00:00 -0800, Yinghai Lu wrote:
    > > > First kernel:
    > > > [ 1.139418] calling init_hw_perf_events+0x0/0xb77 @ 1
    > > > [ 1.159111] Performance Events: PEBS fmt1+, Nehalem events, Intel PMU
    > > > driver.
    > > > [ 1.159567] ... version: 3
    > > > [ 1.179121] ... bit width: 48
    > > > [ 1.179353] ... generic registers: 4
    > > > [ 1.179593] ... value mask: 0000ffffffffffff
    > > > [ 1.199211] ... max period: 000000007fffffff
    > > > [ 1.199554] ... fixed-purpose events: 3
    > > > [ 1.219108] ... event mask: 000000070000000f
    > > > [ 1.219454] initcall init_hw_perf_events+0x0/0xb77 returned 0 after
    > > > 11719 usecs
    > > >
    > > > .....
    > > > [ 20.220997] checking TSC synchronization [CPU#0 -> CPU#11]: passed.
    > > > [ 20.260818] NMI watchdog enabled, takes one hw-pmu counter.
    > > >
    > > > kexeced kernel.
    > > >
    > > >
    > > > [ 1.169470] calling init_hw_perf_events+0x0/0xb77 @ 1
    > > > [ 1.189265] Performance Events: PEBS fmt1+, Nehalem events, Broken
    > > > PMU hardware detected, software events only.
    > > > ...
    > > > [ 21.010407] NMI watchdog failed to create perf event on cpu14:
    > > > fffffffffffffffe
    > > >
    > > > caused by:
    > >
    > > *sigh*, and people ask me why kexec/kdump are such bad ideas..
    > >
    > > apparently kexec doesn't properly shut down the first kernel and leaves
    > > a counter running, then when we write and read the counter value they
    > > don't match because its still running and voila, crap happens.
    > >
    > > I've CC'ed the kexec people, maybe they got clue as to how to sort this.
    >
    > So we can shutdown counters while first kernel is going down. Is there a
    > simple function already which I can call?

    Dunno, the cpu hotplug stuff should suffice I think, but then I don't
    think you actually unplug the boot cpu.

    What does kexec normally do to ensure hardware is left in a sane state?


    \
     
     \ /
      Last update: 2010-12-01 17:13    [W:0.022 / U:90.000 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site