• Hui Wang's avatar
    x86/topology: Use total_cpus for max logical packages calculation · aa02ef09
    Hui Wang authored
    nr_cpu_ids can be limited on the command line via nr_cpus=. This can break the
    logical package management because it results in a smaller number of packages
    while in kdump kernel.
    
    Check below case:
    There is a two sockets system, each socket has 8 cores, which has 16 logical
    cpus while HT was turn on.
    
     0  1  2  3  4  5  6  7     |    16 17 18 19 20 21 22 23
     cores on socket 0               threads on socket 0
     8  9 10 11 12 13 14 15     |    24 25 26 27 28 29 30 31
     cores on socket 1               threads on socket 1
    
    While starting the kdump kernel with command line option nr_cpus=16 panic
    was triggered on one of the cpus 24-31 eg. 26, then online cpu will be
    1-15, 26(cpu 0 was disabled in kdump), ncpus will be 16 and
    __max_logical_packages will be 1, but actually two packages were booted on.
    
    This issue can reproduced by set kdump option nr_cpus=<real physical core
    numbers>, and then trigger panic on last socket's thread, for example:
    
    taskset -c 26 echo c > /proc/sysrq-trigger
    
    Use total_cpus which will not be limited by nr_cpus command line to calculate
    the value of __max_logical_packages.
    Signed-off-by: default avatarHui Wang <john.wanghui@huawei.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: <guijianfeng@huawei.com>
    Cc: <wencongyang2@huawei.com>
    Cc: <douliyang1@huawei.com>
    Cc: <qiaonuohan@huawei.com>
    Link: https://lkml.kernel.org/r/20181107023643.22174-1-john.wanghui@huawei.com
    aa02ef09
smpboot.c 40.7 KB