> From: Thomas Gleixner [mailto:tglx@xxxxxxxxxxxxx] > On Tue, 16 Jan 2018, Joseph Salisbury wrote: > > On 01/16/2018 08:32 AM, Shankar, Ravi V wrote: > > > Vikas on vacation until end of the month. Fenghua will look into > > > this issue. > > > > > > On Jan 16, 2018, at 5:09 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx > > > <mailto:tglx@xxxxxxxxxxxxx>> wrote: > > > > > >> > > >> Vikas, Fenghua can you please look at that ASAP? > > >> > > >> On Sun, 14 Jan 2018, Thomas Gleixner wrote: > > >> > > >>> On Fri, 12 Jan 2018, Joseph Salisbury wrote: > > >>> > > >>>> Hi Vikas, > > >>>> > > >>>> A kernel bug report was opened against Ubuntu [0]. After a > > >>>> kernel bisect, it was found that reverting the following commit > > >>>> resolved this bug: > > >>>> > > >>>> commit 24247aeeabe99eab13b798ccccc2dec066dd6f07 > > >>>> Author: Vikas Shivappa <vikas.shivappa@xxxxxxxxxxxxxxx > > >>>> <mailto:vikas.shivappa@xxxxxxxxxxxxxxx>> > > >>>> Date: Tue Aug 15 18:00:43 2017 -0700 > > >>>> > > >>>> x86/intel_rdt/cqm: Improve limbo list processing > > >>>> > > >>>> > > >>>> The regression was introduced as of v4.14-r1 and still exists > > >>>> with current mainline. The trace with v4.15-rc7 is in comment #44[1]. > > >>>> > > >>>> I was hoping to get your feedback, since you are the patch > > >>>> author. Do you think gathering any additional data will help > > >>>> diagnose this issue, or would it be best to submit a revert request? > > >>> > > >>> That stinks like a use after free. Can you run with KASAN enabled? > > >>> > > >>> Thanks, > > >>> > > >>> tglx > > > > > > Here is some data wiht KASAN enabled: > > https://bugs.launchpad.net/ubuntu/+source/linux- > hwe/+bug/1733662/comme > > nts/51 > > > > Are there any specific logs you would like to see, or specific actions > > executed? > > No, the KASAN output is pretty clear where the issue is. > > Thanks, > > tglx Is this a Haswell specific issue? I run the following test forever without issue on Broadwell and 4.15.0-rc6 with rdt mounted: for ((;;)) do for ((i=1;i<88;i++)) do echo 0 >/sys/devices/system/cpu/cpu$i/online done echo "online cpus:" grep processor /proc/cpuinfo |wc for ((i=1;i<88;i++)) do echo 1 >/sys/devices/system/cpu/cpu$i/online done echo "online cpus:" grep processor /proc/cpuinfo|wc done I'm finding a Haswell to reproduce the issue. Thanks. -Fenghua