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

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Date:   Thu, 24 Feb 2022 16:19:52 +0000
From:   "Moore, Robert" <robert.moore@...el.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>
CC:     "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/4] acpi: exsystem: Warn about sleeps greater than 50 ms

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 */

-----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