Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: NULL pointer dereference in pick_next_task_fair
From:   Valentin Schneider <valentin.schneider@arm.com>
To:     Ram Muthiah <rammuthiah@google.com>,
        Quentin Perret <qperret@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        linux-kernel@vger.kernel.org, aaron.lwe@gmail.com,
        mingo@kernel.org, pauld@redhat.com, jdesfossez@digitalocean.com,
        naravamudan@digitalocean.com, vincent.guittot@linaro.org,
        dietmar.eggemann@arm.com, juri.lelli@redhat.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        kernel-team@android.com, john.stultz@linaro.org
References: <20191028174603.GA246917@google.com>
 <20191029113411.GP4643@worktop.programming.kicks-ass.net>
 <20191029115000.GA11194@google.com>
 <CA+CXyWsoW8ann52pcR66ejRmjJ=4QmoaHTRVhb3=ohe0ZDnm-A@mail.gmail.com>
 <75e99374-0bd6-a7d7-581e-9360a1f90103@arm.com>
 <8d8fe4e9-1905-cde1-9ced-0a860e5a961b@arm.com>
Message-ID: <4f743a74-9b9c-d7e4-bae8-c7ad1d2aeee6@arm.com>
Date:   Thu, 31 Oct 2019 15:24:55 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.9.0
MIME-Version: 1.0
In-Reply-To: <8d8fe4e9-1905-cde1-9ced-0a860e5a961b@arm.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.