ACK[1-2]/cmnt NACK[3]: [PATCH 0/3][SRU][ARTFUL] Fix deadlock on task switches with new microcode

Stefan Bader stefan.bader at
Thu Apr 5 07:04:40 UTC 2018

On 05.04.2018 07:51, Tyler Hicks wrote:
> BugLink:
> [Impact]
> Some systems experience kernel lockups after updating to the latest
> intel-microcode package or when receiving updated microcode from a BIOS update.
> In many cases, the lockups occur before users can reach the login screen which
> makes it very difficult to debug/workaround.
> [Test Case]
> The most reliable test case currently known is to install the sssd package.
> Lockups may occur during package installation (disable IBPB by writing 0 to
> /proc/sys/kernel/ibpb_enabled to prevent this from happening). A lockup will
> most likely occur just after booting the system up as the lock screen is
> displayed.
> [Regression Potential]
> The fix is in the task switching code of the kernel so complexity of the change
> is relatively high.
> [Other Information]
> The third patch fixes what I think was an incomplete backport of 72be211ba.
> That commit added the initialize_tlbstate_and_flush() function but then never
> added any callers of that function.
> I was hopeful that the third patch would fix a resume from hibernation/sleep
> bug (LP: #1748393) but one tester reported that it did not have an effect.

The third patch in this set imo does not belong into this submission. Different
bug references / CVE numbers should always be submitted as their own thread.

About 1-2, the revert should include the same CVE (or BugLink if there were one)
as the follow-up replacement. Only then both will be grouped together in the
changelog. So actually in this case both patches should have both. This (add CVE
line to revert and add BugLink to replacement) can be done when we apply it. So
no need for re-send if there is not anything else which I missed.

> Tyler

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