linux-kernel - Re: [PATCH 3/4] acpi: exsystem: Warn about sleeps greater than 50 ms

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Date:   Fri, 25 Feb 2022 08:38:44 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Robert Moore <robert.moore@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>
Cc:     linux-acpi@...r.kernel.org, devel@...ica.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] acpi: exsystem: Warn about sleeps greater than 50 ms

Dear Robert,


Am 24.02.22 um 17:19 schrieb Moore, Robert:
> So, this is the current implementation:
> 
>      /*
>       * For compatibility with other ACPI implementations and to prevent
>       * accidental deep sleeps, limit the sleep time to something reasonable.
>       */
>      if (HowLong > ACPI_MAX_SLEEP)
>      {
>          HowLong = ACPI_MAX_SLEEP;
>      }
> 
>      AcpiOsSleep (HowLong);
> 
> Where ACPI_MAX_SLEEP is:
> 
> #define ACPI_MAX_SLEEP                  2000    /* 2000 millisec == two seconds */

Exactly. I am not changing it though, but just add a warning.


Kind regards,

Paul


> -----Original Message-----
> From: Paul Menzel <pmenzel@...gen.mpg.de>
> Sent: Thursday, February 24, 2022 3:38 AM
> To: Moore, Robert <robert.moore@...el.com>; Wysocki, Rafael J <rafael.j.wysocki@...el.com>; Len Brown <lenb@...nel.org>
> Cc: Paul Menzel <pmenzel@...gen.mpg.de>; linux-acpi@...r.kernel.org; devel@...ica.org; linux-kernel@...r.kernel.org
> Subject: [PATCH 3/4] acpi: exsystem: Warn about sleeps greater than 50 ms
> 
> Quick boottime is important, so warn about sleeps greater than 50 ms in ACPI.
> 
> 50 ms is still long compared to distribution Linux kernels reaching initrd in 350 ms, so should probably changed to 10 ms, so people are aware about this.
> 
> Signed-off-by: Paul Menzel <pmenzel@...gen.mpg.de>
> ---
>   drivers/acpi/acpica/exsystem.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/acpi/acpica/exsystem.c b/drivers/acpi/acpica/exsystem.c index 00f66af31ffa..bdffb8aac05c 100644
> --- a/drivers/acpi/acpica/exsystem.c
> +++ b/drivers/acpi/acpica/exsystem.c
> @@ -167,6 +167,11 @@ acpi_status acpi_ex_system_do_sleep(u64 how_long_ms)
>   
>   	acpi_ex_exit_interpreter();
>   
> +	if (how_long_ms > 50) {
> +		ACPI_WARNING((AE_INFO,
> +		    "Time parameter %llu > 50 ms. Please contact firmware vendor for more responsive system.", how_long_ms));
> +	}
> +
>   	/*
>   	 * For compatibility with other ACPI implementations and to prevent
>   	 * accidental deep sleeps, limit the sleep time to something reasonable.
> --
> 2.35.1