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Sender: Guenter Roeck <groeck7@gmail.com>
To:     Valentin Schneider <valentin.schneider@arm.com>,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        Frederic Weisbecker <frederic@kernel.org>
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        Ingo Molnar <mingo@kernel.org>,
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From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [tip: sched/core] sched/core: Initialize the idle task with
 preemption disabled
Message-ID: <c9bd8db3-60ae-1dbe-aa2f-f2fe3d5fe2d9@roeck-us.net>
Date:   Wed, 7 Jul 2021 09:35:51 -0700
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On 7/7/21 7:57 AM, Valentin Schneider wrote:
> On 08/07/21 00:35, Alexey Kardashevskiy wrote:
>> On 08/07/2021 00:14, Guenter Roeck wrote:
>>>
>>> Can you reproduce the problem with a powerpc qemu emulation ?
>>> If so, how do you reproduce it there ? Reason for asking is that I don't
>>> see
>>> the problem with any of my powerpc emulations, and I would like to add test
>>> case(s) if possible.
>>
>> I can reproduce the problem on powerpc easily - qemu with "-smp 2" does it.
>>
> 
> So on powerpc I'm chasing a slightly different problem, reported at
> [1]. I couldn't get it to trigger on qemu for powerpc64, and I'm still
> struggling with powerpc. Could you please share you qemu invocation &
> kernel .config? Thanks.
> 

I think I have it. pseries_defconfig, and pseries emulation,
started with "-smp 2" and qemu-system-ppc64:

[    0.731644][    T1] smp: Bringing up secondary CPUs ...^M
[    0.750546][    T0] BUG: scheduling while atomic: swapper/1/0/0x00000000^M
[    0.752119][    T0] no locks held by swapper/1/0.^M
[    0.752309][    T0] Modules linked in:^M
[    0.752684][    T0] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.13.0-11855-g77d34a4683b0 #1^M
[    0.753197][    T0] Call Trace:^M
[    0.753334][    T0] [c000000008737b20] [c0000000009f9b18] .dump_stack_lvl+0xa4/0x100 (unreliable)^M
[    0.754224][    T0] [c000000008737bb0] [c000000000190ed0] .__schedule_bug+0xa0/0xe0^M
[    0.754459][    T0] [c000000008737c30] [c000000001182518] .__schedule+0xc08/0xd90^M
[    0.754738][    T0] [c000000008737d20] [c000000001182b8c] .schedule_idle+0x2c/0x60^M
[    0.754945][    T0] [c000000008737d90] [c0000000001a48ec] .do_idle+0x29c/0x3c0^M
[    0.755145][    T0] [c000000008737e60] [c0000000001a4df0] .cpu_startup_entry+0x30/0x40^M
[    0.755403][    T0] [c000000008737ee0] [c00000000005ef10] .start_secondary+0x2c0/0x300^M
[    0.755621][    T0] [c000000008737f90] [c00000000000d254] start_secondary_prolog+0x10/0x14^M
[    0.764164][    T1] smp: Brought up 1 node, 2 CPUs^M

Guenter