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From:   Josh Don <joshdon@google.com>
Date:   Mon, 1 Mar 2021 13:01:57 -0800
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Subject: Re: [PATCH v10 2/5] sched: CGroup tagging interface for core scheduling
To:     Chris Hyser <chris.hyser@oracle.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
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On Fri, Feb 26, 2021 at 12:08 PM Chris Hyser <chris.hyser@oracle.com> wrote:
>
> Update:
>
> The clone syscall stress test I have is causing a deadlock with this patchset when
> compiled with CONFIG_PROVE_RAW_LOCK_NESTING=y. I am able to get stacktraces with
> nmi_watchdog and am looking through those. Josh was not able to duplicate the
> deadlock, instead getting an actual warning about kmalloc w/GFP_ATOMIC while
> under a raw spinlock in the function __sched_core_update_cookie(). When I retry
> the test with a patch Josh sent, removing the kmalloc() and thus the trigger of
> the warning, no more deadlock. So some combination of CONFIGs, timing and
> function calls seems to have found something in this LOCK proving code.
>
> -chrish

I have a patch to remove the dynamic allocation and overall simplify
the logic here. Will squash that along with the rest of the
modifications suggested by Peter in the next version.