Messages in this thread | | | Subject | Re: perf hw in kexeced kernel broken in tip | From | Peter Zijlstra <> | Date | Wed, 01 Dec 2010 17:11:46 +0100 |
| |
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?
| |