> Hi all, > > I'm having some difficulty tracking down a bug. > > Some configurations of the powerpc kernel since somewhere in the 5.10 > merge window fail to boot on some ppc64 systems. They hang while trying > to bring up SMP. It seems to depend on the RCU_SCALE/PERF_TEST option. > (It was renamed in the 5.10 merge window.) > > I can reproduce it as follows with qemu tcg: > > make -j64 pseries_le_defconfig > scripts/config -m RCU_SCALE_TEST > scripts/config -m RCU_PERF_TEST > make -j 64 vmlinux CC="ccache gcc" > > qemu-system-ppc64 -cpu power9 -M pseries -m 1G -nographic -vga none -smp 4 -kernel vmlinux > > ... > [ 0.036284][ T0] Mount-cache hash table entries: 8192 (order: 0, 65536 bytes, linear) > [ 0.036481][ T0] Mountpoint-cache hash table entries: 8192 (order: 0, 65536 bytes, linear) > [ 0.148168][ T1] POWER9 performance monitor hardware support registered > [ 0.151118][ T1] rcu: Hierarchical SRCU implementation. > [ 0.186660][ T1] smp: Bringing up secondary CPUs ... > <hangs> > I am not sure if that is helpful but i checked it on my x86_64 system using the cross compiled for powerpc Linux kernel: <snip> urezki@pc638:~/data/coding/linux-rcu.git$ powerpc64-linux-gnu-gcc --version powerpc64-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0 Copyright (C) 2018 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. urezki@pc638:~/data/coding/linux-rcu.git$ <snip> with ARCH=powerpc make -j64 pseries_defconfig configuration. I used the 5.10.0-rc1 kernel. <snip> urezki@pc638:~/data/coding/linux-rcu.git$ qemu-system-ppc64 --version QEMU emulator version 3.1.0 (Debian 1:3.1+dfsg-8+deb10u8) Copyright (c) 2003-2018 Fabrice Bellard and the QEMU Project developers urezki@pc638:~/data/coding/linux-rcu.git$ <snip> On my setup i can run the kernel with and without the modules which are in question. So qemu-system-ppc64 -cpu power9 -M pseries -m 1G -nographic -vga none -smp 4 -kernel ./vmlinux works for both cases, with RCU_SCALE and without. Just in case, maybe this information can be useful also. -- Vlad Rezki
