Re: [PATCH] x86/irq: Cure live lock in irq_force_complete_move()

[Thomas Gleixner]

On Fri, 11 Mar 2016, Luck, Tony wrote:
> With this patch applied my system survives me doing
> several rounds of:
> 
> # echo 0 | tee /sys/devices/system/cpu/cpu*/online
> # echo 1 | tee /sys/devices/system/cpu/cpu*/online
> 
> whereas without the patch the first of those went to
> 
> [152455.129604] NMI watchdog: Watchdog detected hard LOCKUP on cpu 96
> [152455.136943] Kernel panic - not syncing: Hard LOCKUP
> 
> I'm not sure we care to optimize the cpu offline path, but I'll note here
> that taking all (but one) cpus offline took 52 seconds (for a hundred
> and mumble logical cpus).  Bringing them all back is just 4 seconds.
> 
> Tested-by: Tony Luck <tony.luck@xxxxxxxxx>

Unfortunately while it cures the livelock it's still not correct.

/me goes back to the drawing board