ACK: [SRU][Bionic][PATCH 0/2] Fix IO hang regression

[Colin Ian King]

On 21/04/18 22:08, Seth Forshee wrote:
> BugLink: http://bugs.launchpad.net/bugs/1765232
> 
> Impact: Since 4.15.0-15 some machines have been failing to boot due to
> IO hangs. This is caused by patches applied for LP #1759723, which
> assigned managed interrupt vectors and reply queues for all possible
> CPUs, not just present CPUs. Some drivers were not prepared to cope with
> this and end up selecting reply queues not mapped to an online CPU,
> causing IO hangs during boot.
> 
> Fix: There are driver fixes available upstream, but there are 8-ish
> patches in total and we're extremely close to release, so the safer bet
> it to just revert the patches for LP #1759723. We can consider
> reintroducing them with required fixes at a later time.
> 
> Regression Potential: This is obviously going to reintroduce the problem
> the patches were intended to fix. These are less serious than the
> problems which the patches introduced, and IBM has given their okay to
> revert them as well.
> 
> Test Case: Verified to fix affected hardware on LP #1765232.
> 
> Thanks,
> Seth
> 
> 
> Seth Forshee (2):
>   Revert "blk-mq: simplify queue mapping & schedule with each possisble
>     CPU"
>   Revert "genirq/affinity: assign vectors to all possible CPUs"
> 
>  block/blk-mq.c        | 19 +++++++++++--------
>  kernel/irq/affinity.c | 30 +++++++++++++++---------------
>  2 files changed, 26 insertions(+), 23 deletions(-)
> 
> 
Seems like the best solution for the moment.

Acked-by: Colin Ian King <colin.king at canonical.com>