On 4/23/19 2:48 PM, John Ogness wrote:
On 2019-04-22, Hongzhi, Song <hongzhi.song@xxxxxxxxxxxxx> wrote:
Anyone notice this issue?
Yes, I am aware of the issue. It is actually a feature, not a bug. ;-)
Individual LOG_CONT messages, when classified as emergency messages, are
printed immediately to the console.
Yes, this is what I have acquired from commit log and code.
The emergency mechanism is a good way.
This makes them appear
"disorderly". It is not yet clear how best to deal with LOG_CONT
emergency messages.
Extracting a part of log from my LOG_CONT message,
[ 0.761635] 000: (family: 0x6, model: 0xf
[ 0.761635] 000: , stepping: 0xb)
It obviously separates a full line. Maybe it is not related to LOG_CONT. ^_^
The counterpart source code:
1499 pr_cont(" (family: 0x%x, model: 0x%x", c->x86, c->x86_model);
1500
1501 if (c->x86_stepping || c->cpuid_level >= 0)
1502 pr_cont(", stepping: 0x%x)\n", c->x86_stepping);
1503 else
1504 pr_cont(")\n");
I don't know if the issue exists in other place except LOG_CONT.
But it indeed influences customer's judgement.
Thanks for you reply.
--Hongzhi
But I suppose we should introduce a config option to
disable atomic consoles altogether if users preferred buffered/delayed
printk output.
John Ogness
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@pek-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
