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Date:   Tue, 23 Feb 2021 10:05:29 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Chris Hyser <chris.hyser@oracle.com>
Cc:     "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        Nishanth Aravamudan <naravamudan@digitalocean.com>,
        Julien Desfossez <jdesfossez@digitalocean.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Vineeth Pillai <viremana@linux.microsoft.com>,
        Aaron Lu <aaron.lwe@gmail.com>,
        Aubrey Li <aubrey.intel@gmail.com>, tglx@linutronix.de,
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        keescook@chromium.org, kerrnel@google.com,
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        Valentin Schneider <valentin.schneider@arm.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
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        Chen Yu <yu.c.chen@intel.com>,
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        Hao Luo <haoluo@google.com>,
        Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH v10 2/5] sched: CGroup tagging interface for core
 scheduling
Message-ID: <YDTFWZPdmrDuYd91@hirez.programming.kicks-ass.net>
References: <20210123011704.1901835-1-joel@joelfernandes.org>
 <20210123011704.1901835-3-joel@joelfernandes.org>
 <0e91838e-4cca-4c3b-cb36-226c098f36c9@oracle.com>
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On Mon, Feb 22, 2021 at 11:00:37PM -0500, Chris Hyser wrote:
> On 1/22/21 8:17 PM, Joel Fernandes (Google) wrote:
> While trying to test the new prctl() code I'm working on, I ran into a bug I
> chased back into this v10 code. Under a fair amount of stress, when the
> function __sched_core_update_cookie() is ultimately called from
> sched_core_fork(), the system deadlocks or otherwise non-visibly crashes.
> I've not had much success figuring out why/what. I'm running with LOCKDEP on
> and seeing no complaints. Duplicating it only requires setting a cookie on a
> task and forking a bunch of threads ... all of which then want to update
> their cookie.

Can you share the code and reproducer?