linux-kernel - Re: NULL pointer dereference in pick_next_task

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Message-ID: <4f743a74-9b9c-d7e4-bae8-c7ad1d2aeee6@arm.com>
Date:   Thu, 31 Oct 2019 15:24:55 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Ram Muthiah <rammuthiah@...gle.com>,
        Quentin Perret <qperret@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, aaron.lwe@...il.com,
        mingo@...nel.org, pauld@...hat.com, jdesfossez@...italocean.com,
        naravamudan@...italocean.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, juri.lelli@...hat.com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        kernel-team@...roid.com, john.stultz@...aro.org
Subject: Re: NULL pointer dereference in pick_next_task_fair

On 31/10/2019 11:54, Valentin Schneider wrote:
> On 31/10/2019 02:33, Valentin Schneider wrote:
>> For wakeups, select_task_rq_fair() can only ever pick prev_cpu or this_cpu
>> since there are no sched domains. I don't see many candidates that could
>> wakeup on a secondary (thus have non-zero this_cpu) this early there. 

And another fail here, this doesn't have to be at secondary bringup, it's 
just that the bringup will always be in the idle task's callstack (if the
timestamps weren't enough of a clue already). I guess I'll stop writing
nonsense and keep staring in silence.