Dear Paul I am also very interested in the topic. The Open source lab of Oregon State University has lent me a 8 core power ppc64el VM for 3 months, I guess I can try reproducing this bug in the Virtual Machine by executing qemu in non hardware accelerated mode (using -no-kvm argument). I am currently doing research on https://lore.kernel.org/rcu/20220201175023.GW4285@paulmck-ThinkPad-P17-Gen-1/T/#mc7e5f8ec99e3794bec1e38fbbb130e71172e4759, I think I can give a preliminary short report on that previous topic tomorrow. And I am very interested in doing a search on the new topic the day after tomorrow. Thank you both for providing me an opportunity to improve myself ;-) Thanks again Zhouyi On Tue, Feb 8, 2022 at 12:10 PM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: > > On Mon, Feb 07, 2022 at 05:44:47PM +0100, Paul Menzel wrote: > > Dear Linux folks, > > > > > > On the POWER8 server IBM S822LC running Ubuntu 21.10, building Linux > > 5.17-rc2+ with rcutorture tests > > > > $ tools/testing/selftests/rcutorture/bin/torture.sh --duration 10 > > > > the built init > > > > $ file tools/testing/selftests/rcutorture/initrd/init > > tools/testing/selftests/rcutorture/initrd/init: ELF 64-bit LSB > > executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), statically > > linked, BuildID[sha1]=0ded0e45649184a296f30d611f7a03cc51ecb616, for > > GNU/Linux 3.10.0, stripped > > > > segfaults in QEMU. From one of the log files > > > > > > /dev/shm/linux/tools/testing/selftests/rcutorture/res/2022.02.01-21.52.37-torture/results-rcutorture/TREE03/console.log > > > > [ 1.119803][ T1] Run /init as init process > > [ 1.122011][ T1] init[1]: segfault (11) at f0656d90 nip 10000a18 > > lr 0 code 1 in init[10000000+d0000] > > [ 1.124863][ T1] init[1]: code: 2c2903e7 f9210030 4081ff84 > > 4bffff58 00000000 01000000 00000580 3c40100f > > [ 1.128823][ T1] init[1]: code: 38427c00 7c290b78 782106e4 > > 38000000 <f821ff81> 7c0803a6 f8010000 e9028010 > > > > Executing the init, which just seems to be an endless loop, from userspace > > work: > > > > $ strace ./tools/testing/selftests/rcutorture/initrd/init > > execve("./tools/testing/selftests/rcutorture/initrd/init", > > ["./tools/testing/selftests/rcutor"...], 0x7ffffdb9e860 /* 31 vars */) = 0 > > brk(NULL) = 0x1001d940000 > > brk(0x1001d940b98) = 0x1001d940b98 > > set_tid_address(0x1001d9400d0) = 2890832 > > set_robust_list(0x1001d9400e0, 24) = 0 > > uname({sysname="Linux", > > nodename="flughafenberlinbrandenburgwillybrandt.molgen.mpg.de", ...}) = 0 > > prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, > > rlim_max=RLIM64_INFINITY}) = 0 > > readlink("/proc/self/exe", "/dev/shm/linux/tools/testing/sel"..., 4096) > > = 61 > > getrandom("\xf1\x30\x4c\x9e\x82\x8d\x26\xd7", 8, GRND_NONBLOCK) = 8 > > brk(0x1001d970b98) = 0x1001d970b98 > > brk(0x1001d980000) = 0x1001d980000 > > mprotect(0x100e0000, 65536, PROT_READ) = 0 > > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=1, tv_nsec=0}, > > 0x7ffffb22c8a8) = 0 > > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=1, tv_nsec=0}, > > 0x7ffffb22c8a8) = 0 > > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=1, tv_nsec=0}, ^C{tv_sec=0, > > tv_nsec=872674044}) = ? ERESTART_RESTARTBLOCK (Interrupted by signal) > > strace: Process 2890832 detached > > Huh. In PowerPC, is there some difference between system calls > executed in initrd and those same system calls executed in userspace? > > And just to make sure, the above strace was from exactly the same > binary "init" file that is included in initrd, correct? > > Adding Willy Tarreau for his thoughts. > > Thanx, Paul > > > Any ideas, what `mkinitrd.sh` [2] should do differently? > > > > ``` > > cat > init.c << '___EOF___' > > #ifndef NOLIBC > > #include <unistd.h> > > #include <sys/time.h> > > #endif > > > > volatile unsigned long delaycount; > > > > int main(int argc, int argv[]) > > { > > int i; > > struct timeval tv; > > struct timeval tvb; > > > > for (;;) { > > sleep(1); > > /* Need some userspace time. */ > > if (gettimeofday(&tvb, NULL)) > > continue; > > do { > > for (i = 0; i < 1000 * 100; i++) > > delaycount = i * i; > > if (gettimeofday(&tv, NULL)) > > break; > > tv.tv_sec -= tvb.tv_sec; > > if (tv.tv_sec > 1) > > break; > > tv.tv_usec += tv.tv_sec * 1000 * 1000; > > tv.tv_usec -= tvb.tv_usec; > > } while (tv.tv_usec < 1000); > > } > > return 0; > > } > > ___EOF___ > > > > # build using nolibc on supported archs (smaller executable) and fall > > # back to regular glibc on other ones. > > if echo -e "#if __x86_64__||__i386__||__i486__||__i586__||__i686__" \ > > "||__ARM_EABI__||__aarch64__\nyes\n#endif" \ > > | ${CROSS_COMPILE}gcc -E -nostdlib -xc - \ > > | grep -q '^yes'; then > > # architecture supported by nolibc > > ${CROSS_COMPILE}gcc -fno-asynchronous-unwind-tables -fno-ident \ > > -nostdlib -include ../../../../include/nolibc/nolibc.h \ > > -s -static -Os -o init init.c -lgcc > > else > > ${CROSS_COMPILE}gcc -s -static -Os -o init init.c > > fi > > ``` > > > > > > Kind regards, > > > > Paul > > > > > > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/rcutorture/doc/initrd.txt > > [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/rcutorture/bin/mkinitrd.sh
