Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S932773AbdCGPGR (ORCPT <rfc822;w@1wt.eu>);
        Tue, 7 Mar 2017 10:06:17 -0500
Received: from mail-qk0-f172.google.com ([209.85.220.172]:35848 "EHLO
        mail-qk0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S932588AbdCGPFh (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 7 Mar 2017 10:05:37 -0500
MIME-Version: 1.0
In-Reply-To: <CAGkQfmPP7w09xutsK5OhfWzNfCyC3Bj8VmoFxDiB5eqAFnZBbQ@mail.gmail.com>
References: <CAGkQfmPP7w09xutsK5OhfWzNfCyC3Bj8VmoFxDiB5eqAFnZBbQ@mail.gmail.com>
From: Romain Izard <romain.izard.pro@gmail.com>
Date: Tue, 7 Mar 2017 16:05:10 +0100
X-Google-Sender-Auth: hRE-niAXbLhgd9hP3EAFf4uuo7g
Message-ID: <CAGkQfmMxame-m+Te59EnFACqmk9TU-3Mhi6BctQWDPKuy38FXg@mail.gmail.com>
Subject: Re: Warning on boot on SAMA5D2 with Linux 4.11-rc1
To: linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        David Engraf <david.engraf@sysgo.com>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2055
Lines: 46

2017-03-06 12:28 GMT+01:00 Romain Izard <romain.izard.pro@gmail.com>:
>
> While looking for another issue, I tried Linux 4.11-rc1 on a SAMA5D2 Xplained
> board. The boot log contains the following warning:
>
> [    0.100000] ------------[ cut here ]------------
> [    0.100000] WARNING: CPU: 0 PID: 1 at
> ../kernel/time/sched_clock.c:180 sched_clock_register+0x44/0x1e4
> [    0.100000] CPU: 0 PID: 1 Comm: swapper Not tainted 4.11.0-rc1+ #3
> [    0.100000] Hardware name: Atmel SAMA5
> [    0.100000] [<c010c494>] (unwind_backtrace) from [<c010a558>]
> (show_stack+0x10/0x14)
> [    0.100000] [<c010a558>] (show_stack) from [<c0115654>] (__warn+0xe0/0xf8)
> [    0.100000] [<c0115654>] (__warn) from [<c011571c>]
> (warn_slowpath_null+0x20/0x28)
> [    0.100000] [<c011571c>] (warn_slowpath_null) from [<c090b0d0>]
> (sched_clock_register+0x44/0x1e4)
> [    0.100000] [<c090b0d0>] (sched_clock_register) from [<c091fb98>]
> (tcb_clksrc_init+0x1ac/0x360)
> [    0.100000] [<c091fb98>] (tcb_clksrc_init) from [<c0900d8c>]
> (do_one_initcall+0xb4/0x15c)
> [    0.100000] [<c0900d8c>] (do_one_initcall) from [<c0900f68>]
> (kernel_init_freeable+0x134/0x1c4)
> [    0.100000] [<c0900f68>] (kernel_init_freeable) from [<c06bfc64>]
> (kernel_init+0x8/0x10c)
> [    0.100000] [<c06bfc64>] (kernel_init) from [<c0107318>]
> (ret_from_fork+0x14/0x3c)
> [    0.100000] ---[ end trace 7ce9be9d7cf6f800 ]---
> [    0.100012] sched_clock: 32 bits at 10MHz, resolution 96ns, wraps
> every 206986376143ns
>
> This is related to the following commit:
> 7b9f1d16e6d1 clocksource/drivers/tcb_clksrc: Use 32 bit tcb as sched_clock
>
> When we call sched_clock_register from tcb_clksrc_init from
> arch_initcall, we are too late as sched expects all the candidates for
> its clock to be registered before interrupts are enabled. This warning
> does not prevent the tcb clock from being used.
>

After some more use with 4.11-rc1, I also noticed that the timestamp for
printk rolls over to 0 after only 413s. Reverting the aforementioned commit
fixes it.

-- 
Romain Izard