* Huang Ying <ying.hu...@intel.com> wrote:
> FYI, we noticed the below changes on
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/apic
> commit f5d6a52f511157c7476590532a23b5664b1ed877 ("x86/smpboot: Skip delays
> during SMP initialization similar to Xen")
>
>
> +------------------------------------------------+------------+------------+
> | | 19e3d60d49 | f5d6a52f51 |
> +------------------------------------------------+------------+------------+
> | boot_successes | 20 | 10 |
> | boot_failures | 2 | 12 |
> | IP-Config:Auto-configuration_of_network_failed | 2 | 2 |
> | BUG:kernel_boot_hang | 0 | 10 |
> +------------------------------------------------+------------+------------+
>
>
> [ 0.000000] Initializing CPU#1
> [ 1.586595] kvm-clock: cpu 1, msr 0:13fdf041, secondary cpu clock
>
> BUG: kernel boot hang
> Elapsed time: 305
> qemu-system-i386 -enable-kvm -kernel
> /pkg/linux/i386-randconfig-c0-05111038/gcc-4.9/be67584d15684730aeed88cab355c5de8b0491fe/vmlinuz-4.1.0-rc3-01147-gbe67584
> -append 'root=/dev/ram0 user=lkp
> job=/lkp/scheduled/vm-kbuild-yocto-i386-3/rand_boot-1-yocto-minimal-i386.cgz-i386-randconfig-c0-05111038-be67584d15684730aeed88cab355c5de8b0491fe-1-20150512-31766-1fzr1qi.yaml
> ARCH=i386 kconfig=i386-randconfig-c0-05111038
> branch=linux-devel/devel-cairo-smoke-201505120219
> commit=be67584d15684730aeed88cab355c5de8b0491fe
> BOOT_IMAGE=/pkg/linux/i386-randconfig-c0-05111038/gcc-4.9/be67584d15684730aeed88cab355c5de8b0491fe/vmlinuz-4.1.0-rc3-01147-gbe67584
> max_uptime=600
> RESULT_ROOT=/result/boot/1/vm-kbuild-yocto-i386/yocto-minimal-i386.cgz/i386-randconfig-c0-05111038/gcc-4.9/be67584d15684730aeed88cab355c5de8b0491fe/0
> LKP_SERVER=inn earlyprintk=ttyS0,115200 systemd.log_level=err debug
> apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 panic=-1
> softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2
> prompt_ramdisk=0 console=ttyS0,115200 console=tty0 vga=normal rw
> ip=::::vm-kbuild-yocto-i386-3::dhcp drbd.minor_count=8' -initrd
> /fs/sdc1/initrd-vm-kbuild-yocto-i386-3 -m 320 -smp 2 -device
> e1000,netdev=net0 -netdev user,id=net0 -boot order=nc -no-reboot -watchdog
> i6300esb -rtc base=localtime -drive
> file=/fs/sdc1/disk0-vm-kbuild-yocto-i386-3,media=disk,if=virtio -pidfile
> /dev/shm/kboot/pid-vm-kbuild-yocto-i386-3 -serial
> file:/dev/shm/kboot/serial-vm-kbuild-yocto-i386-3 -daemonize -display none
> -monitor null
Hm, so in hindsight the commit, contrary to the changelog, not only
changed delays, but also changed the APIC_DM_INIT logic from:
...
apic_icr_write(APIC_INT_LEVELTRIG | APIC_DM_INIT, phys_apicid);
...
to:
if (!cpu_has_x2apic) {
...
apic_icr_write(APIC_INT_LEVELTRIG | APIC_DM_INIT, phys_apicid);
...
}
i.e. in the x2apic case it not only skips the delays, but skips the
INIT IPI deassertion as well!
So I think this change was poorly tested (and the semantic change
slipped through my review as well), in a very fragile piece of
historic code, so I've reverted it.
Len's 10 msec delay optimization for modern x86 CPUs is kept intact.
Thanks,
Ingo
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