linux-kernel - Re: Bug report: A commit about serial8250 cause the output disorderly at the phase of startup

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Date:   Mon, 22 Apr 2019 09:12:38 +0800
From:   "Hongzhi, Song" <hongzhi.song@...driver.com>
To:     <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        <john.ogness@...utronix.de>, <bigeasy@...utronix.de>
Subject: Re: Bug report: A commit about serial8250 cause the output disorderly
 at the phase of startup

Hi all,

Anyone notice this issue?


--Hongzhi


On 4/19/19 10:24 AM, Hongzhi, Song wrote:
> 1. Issue description:
>
> Boot kernel( >= linux-rt-devel-v5.0.3 ) with qemu.
> Then qemu will print following disorderly messages.
>
> At the beginning, the messages are disorderly. But then it becomes 
> normally from printing "[    0.000000] 000: Linux version..."
>
> --------------------------------------------------
> [    0.019000] 000: tsc: Unable to calibrate against PIT
> [    0.002583] 000: 6199.83 BogoMIPS (lpj=3099918)
> [    0.521247] 000: Intel(R) Core(TM)2 Duo CPU     T7700  @ 2.40GHz
> [    0.521247] 000:  (family: 0x6, model: 0xf
> [    0.521247] 000: , stepping: 0xb)
> [    0.533126] 000: unsupported p6 CPU model 15
> [    0.533318] 000: no PMU driver, software events only.
> [    0.765082] 000: 1 ACPI AML tables successfully acquired and loaded
> [    0.765274] 000:
> [    0.785903] 000: Enabled 2 GPEs in block 00 to 0F
> [    0.786128] 000:
> [    0.835675] 000: acpi PNP0A03:00: fail to add MMCONFIG information, 
> can't access extended PCI configuration space under this bridge.
> [    0.892056] 000:  5
> [    0.892289] 000:  *10
> [    0.892416] 000:  11
> [    0.892527] 000: )
> [    0.892661] 000:
>
> /* skip some repeated contents */
>
> [    5.052149] 000: , 512kB Cache
> [    0.000000] 000: Linux version 5.0.3-yocto-preempt-rt+ 
> (hsong@...-lpggp1) (gcc version 8.3.0 (GCC)) #24 SMP PREEMPT Thu Apr 
> 18 03:29:58 EDT 2019
> [    0.000000] 000: Command line: root=/dev/vda rw highres=off 
> console=ttyS0 mem=256M ip=192.168.7.4::192.168.7.3:255.255.255.0 vga=0 
> uvesafb.mode_opti0
> [    0.000000] 000: x86/fpu: x87 FPU will use FXSAVE
> [    0.000000] 000: BIOS-provided physical RAM map:
> [    0.000000] 000: BIOS-e820: [mem 
> 0x0000000000000000-0x000000000009fbff]
> [    0.000000] 000: BIOS-e820: [mem 
> 0x000000000009fc00-0x000000000009ffff]
> [    0.000000] 000: BIOS-e820: [mem 
> 0x00000000000f0000-0x00000000000fffff]
> [    0.000000] 000: BIOS-e820: [mem 
> 0x0000000000100000-0x000000000ffdbfff]
>
> --------------------------------------------------
>
> 2. Reproduce:
> (1)build kernel: (Attachment is my .config)
> make ARCH=x86_64 
> CROSS_COMPILE=[path-to-my-cross-toolchain]/x86_64-wrs-linux-
>
> (2)boot kernel with qemu:
>
> qemu-system-x86_64 \
> -drive file=qemux86-64.rootfs.ext4,if=virtio,format=raw \
> -nographic \
> -kernel arch/x86/boot/bzImage \
> -append 'root=/dev/vda rw highres=off  console=ttyS0 mem=256M ip=dhcp'
>
> 3. Analysis:
> I find the following commit from >=linux-rt-devel-v5.0.3. cause the 
> issue.
>
> b9d460e serial: 8250: implement write_atomic
>