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. This makes them appear "disorderly". It is not yet clear how best to deal with LOG_CONT emergency messages. 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
