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Message-ID: <8b0e1945-d4ef-2aef-fb5d-1b6b8397b169@linux.ibm.com>
Date:   Mon, 26 Sep 2022 15:54:10 +0200
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Subject: Re: [PATCH v3 6/6] freezer,sched: Rewrite core freezer logic
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To:     Peter Zijlstra <peterz@infradead.org>
Cc:     bigeasy@linutronix.de, dietmar.eggemann@arm.com,
        ebiederm@xmission.com, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org, mgorman@suse.de, mingo@kernel.org,
        oleg@redhat.com, rjw@rjwysocki.net, rostedt@goodmis.org,
        tj@kernel.org, vincent.guittot@linaro.org, will@kernel.org,
        Marc Hartmayer <mhartmay@linux.ibm.com>,
        Amit Shah <amit@kernel.org>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>
References: <20220822114649.055452969@infradead.org>
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 <56576c3c-fe9b-59cf-95b8-158734320f24@linux.ibm.com>
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 <66463973-923f-624d-3041-72ce76147b3e@linux.ibm.com>
 <YzGrJSLXpocpGIha@hirez.programming.kicks-ass.net>
From:   Christian Borntraeger <borntraeger@linux.ibm.com>
In-Reply-To: <YzGrJSLXpocpGIha@hirez.programming.kicks-ass.net>
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Am 26.09.22 um 15:37 schrieb Peter Zijlstra:
> On Mon, Sep 26, 2022 at 03:23:10PM +0200, Christian Borntraeger wrote:
>> Am 26.09.22 um 14:55 schrieb Peter Zijlstra:
>>
>>> Could you please test with something like the below on? I can boot that
>>> with KVM, but obviously I didn't suffer any weirdness to begin with :/
>>>
>>> ---
>>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>>> index 4e6a6417211f..ef9ccfc3a8c0 100644
>>> --- a/kernel/sched/core.c
>>> +++ b/kernel/sched/core.c
>>> @@ -4051,6 +4051,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
>>>    	unsigned long flags;
>>>    	int cpu, success = 0;
>>> +	WARN_ON_ONCE(state & TASK_FREEZABLE);
>>> +
>>>    	preempt_disable();
>>>    	if (p == current) {
>>>    		/*
>>
>> Does not seem to trigger.
> 
> Moo -- quite the puzzle this :/ I'll go stare at it more then.

In the end this is about the end of the sshd process (shutting it down).
I can also trigger the problem by sending a SIGTERM so its not about
the shutdown itself.
Pofiling the guest I see scheduler functions like sched_clock, pick_next_entity,
update_min_vruntime and so on with 100% system time.