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

[Kleber Souza]

On 04/05/18 07:51, Tyler Hicks wrote:
> BugLink: https://bugs.launchpad.net/bugs/1759920
> 
> [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.
> 
> Tyler
> 
> 

With same comments as Stefan:

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>