Re: [PATCH] sd: Fix a disk probing hang

[Bart Van Assche <Bart.VanAssche@wdc.com>]

On Wed, 2017-11-08 at 09:12 +0100, Hannes Reinecke wrote:
> You know, this actually looks like the same issue I'm chasing with iser;
> we have a customer who regularly sees lockups during scanning.
> As it turns out, iser is calling scsi_device_del() from the RX thread.
> Which in turn needs to call async_synchronize().
> If a disk scan is running at the same time we have a nice deadlock, as
> the RX thread can't move forward before aynch_synchronize() returns,
> which it'll never do as the scan cannot complete.
> I've tried to fix that by having the async probing only waiting for that
> particular instance (look for patch 'sd: use async_probe cookie to avoid
> deadlocks'), but this wasn't greeted with much enthusiasm.

Hello Hannes,

Since I applied Roman Penyaev's patch "[PATCH 1/1] [RFC] blk-mq: fix queue
stalling on shared hctx restart" I have not been able to reproduce this hang.
I will let you know if I would run into this hang again.

Bart.