Re: Deadlock in wbt / rq-qos

On Tue, Jun 15, 2021 at 06:42:40AM -0700, Omar Kilani wrote:

Hi Ming,

It looks to be the same issue based on the log timelines. I *think* that
patch will fix it but it’s really subtle so I’ll test.

I can only trigger this on an AMD Milan machine for some reason that I
don’t understand. Sometimes in 800 seconds, sometimes in 5 hours.

I have a new build with printk’s on the atomic_inc_below to check the
acquire condition.

I’ll add that patch and re-test. But I couldn’t find that change in the
linux-block git? Is it in a specific branch?

The patch is in the branch of for-5.14/block:

https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-5.14/block&id=11c7aa0ddea8611007768d3e6b58d45dc60a19e1

Thanks,
Ming

Hi Ming,

I can confirm after a day of running my repro tests that the patch has
fixed the issue.

Thank you Jan.

Regards,
Omar

On Tue, Jun 15, 2021 at 7:07 AM Ming Lei [off-list ref] wrote:

On Tue, Jun 15, 2021 at 06:42:40AM -0700, Omar Kilani wrote:

quoted

Hi Ming,

It looks to be the same issue based on the log timelines. I *think* that
patch will fix it but it’s really subtle so I’ll test.

I can only trigger this on an AMD Milan machine for some reason that I
don’t understand. Sometimes in 800 seconds, sometimes in 5 hours.

I have a new build with printk’s on the atomic_inc_below to check the
acquire condition.

I’ll add that patch and re-test. But I couldn’t find that change in the
linux-block git? Is it in a specific branch?

The patch is in the branch of for-5.14/block:

https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-5.14/block&id=11c7aa0ddea8611007768d3e6b58d45dc60a19e1

Thanks,
Ming