linux-kernel - Re: [PM] bfcc1e67ff: kernel-selftests.breakpoints.step_after_suspend

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Date:   Fri, 15 Oct 2021 12:40:00 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        lkp@...ts.01.org, lkp@...el.com,
        kernel test robot <oliver.sang@...el.com>
Subject: Re: [PM] bfcc1e67ff:
 kernel-selftests.breakpoints.step_after_suspend_test.fail

On 10/15/21 11:45 AM, Rafael J. Wysocki wrote:
> On 10/14/2021 11:55 PM, Florian Fainelli wrote:
>> On 10/14/21 12:23 PM, Rafael J. Wysocki wrote:
>>> On 10/14/2021 6:26 PM, Florian Fainelli wrote:
>>>> On 10/14/21 12:57 AM, kernel test robot wrote:
>>>>> Greeting,
>>>>>
>>>>> FYI, we noticed the following commit (built with gcc-9):
>>>>>
>>>>> commit: bfcc1e67ff1e4aa8bfe2ca57f99390fc284c799d ("PM: sleep: Do not
>>>>> assume that "mem" is always present")
>>>>> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git
>>>>> master
>>>>>
>>>>>
>>>>> in testcase: kernel-selftests
>>>>> version: kernel-selftests-x86_64-c8c9111a-1_20210929
>>>>> with following parameters:
>>>>>
>>>>>      group: group-00
>>>>>      ucode: 0x11
>>>>>
>>>>> test-description: The kernel contains a set of "self tests" under the
>>>>> tools/testing/selftests/ directory. These are intended to be small
>>>>> unit tests to exercise individual code paths in the kernel.
>>>>> test-url: https://www.kernel.org/doc/Documentation/kselftest.txt
>>>>>
>>>>>
>>>>> on test machine: 288 threads 2 sockets Intel(R) Xeon Phi(TM) CPU 7295
>>>>> @ 1.50GHz with 80G memory
>>>>>
>>>>> caused below changes (please refer to attached dmesg/kmsg for entire
>>>>> log/backtrace):
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> If you fix the issue, kindly add following tag
>>>>> Reported-by: kernel test robot <oliver.sang@...el.com>
>>>> Thanks for your report. Assuming that the code responsible for
>>>> registering the suspend operations is drivers/acpi/sleep.c for your
>>>> platform, and that acpi_sleep_suspend_setup() iterated over all
>>>> possible
>>>> sleep states, your platform must somehow be returning that
>>>> ACPI_STATE_S3
>>>> is not a supported state somehow?
>>>>
>>>> Rafael have you ever encountered something like that?
>>> Yes, there are systems with ACPI that don't support S3.
>> OK and do you know what happens when we enter suspend with "mem" in
>> those cases? Do we immediately return because ultimately the firmware
>> does not support ACPI S3?
> 
> "mem" should not be present in the list of available strings then, so it
> should be rejected right away.

Well yes, that was the purpose of the patch I submitted, but assuming
that we did provide "mem" as one of the possible standby modes even
though that was wrong (before patch), and the test was trying to enter
ACPI S3 standby, what would have happened, would the ACPI firmware honor
the request but return an error, or would it actually enter ACPI S3?

In any case, I will change the test to check that this is a supported
standby mode before trying it.
-- 
Florian