linux-kernel - Re: [PATCH] ACPI, APEI, EINJ: Relax platform response timeout to 1 second.

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Date:   Sun, 17 Oct 2021 12:06:52 +0800
From:   Shuai Xue <xueshuai@...ux.alibaba.com>
To:     "Luck, Tony" <tony.luck@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "bp@...en8.de" <bp@...en8.de>,
        "james.morse@....com" <james.morse@....com>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>
Cc:     "zhangliguang@...ux.alibaba.com" <zhangliguang@...ux.alibaba.com>,
        "zhuo.song@...ux.alibaba.com" <zhuo.song@...ux.alibaba.com>
Subject: Re: [PATCH] ACPI, APEI, EINJ: Relax platform response timeout to 1
 second.

Hi, Tony,

Thank you for your reply.

> Spinning for 1ms was maybe ok. Spinning for up to 1s seems like a bad idea.
>
> This code is executed inside a mutex ... so maybe it is safe to sleep instead of spin?

May the email Subject misled you. This code do NOT spin for 1 sec. The period of the
spinning depends on the SPIN_UNIT.

> -#define SPIN_UNIT		100			/* 100ns */
> -/* Firmware should respond within 1 milliseconds */
> -#define FIRMWARE_TIMEOUT	(1 * NSEC_PER_MSEC)
> +#define SPIN_UNIT		100			/* 100us */
> +/* Firmware should respond within 1 seconds */
> +#define FIRMWARE_TIMEOUT	(1 * USEC_PER_SEC)

The period was 100 ns and changed to 100 us now. In my opinion, spinning for 100 ns or 100 us is OK :)

The timeout_default is set with FIRMWARE_TIMEOUT (1 sec) by default. If the platform do not
respond within timeout_default after multiple spins, the OSPM will print a warning message to
dmesg.

Regards,
Shuai


On 2021/10/15 PM11:37, Luck, Tony wrote:
>> We observe that the waiting time for DDR error injection is about 10 ms
>> and that for PCIe error injection is about 500 ms in Arm platfrom.
>>
>> In this patch, we relax the response timeout to 1 second and allow user to
>> pass the time out value as a argument.
> 
> Spinning for 1ms was maybe ok. Spinning for up to 1s seems like a bad idea.
> 
> This code is executed inside a mutex ... so maybe it is safe to sleep instead of spin?
> 
> -Tony
>