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    MIPS: Build uasm-generated code only once to avoid CPU Hotplug problem · 8759934e
    Huacai Chen 提交于
    This and the next patch resolve memory corruption problems while CPU
    hotplug. Without these patches, memory corruption can triggered easily
    as below:
    
    On a quad-core MIPS platform, use "spawn" of UnixBench-5.1.3 (http://
    code.google.com/p/byte-unixbench/) and a CPU hotplug script like this
    (hotplug.sh):
    while true; do
    echo 0 >/sys/devices/system/cpu/cpu1/online
    echo 0 >/sys/devices/system/cpu/cpu2/online
    echo 0 >/sys/devices/system/cpu/cpu3/online
    sleep 1
    echo 1 >/sys/devices/system/cpu/cpu1/online
    echo 1 >/sys/devices/system/cpu/cpu2/online
    echo 1 >/sys/devices/system/cpu/cpu3/online
    sleep 1
    done
    
    Run "hotplug.sh" and then run "spawn 10000", spawn will get segfault
    after a few minutes.
    
    This patch:
    Currently, clear_page()/copy_page() are generated by Micro-assembler
    dynamically. But they are unavailable until uasm_resolve_relocs() has
    finished because jump labels are illegal before that. Since these
    functions are shared by every CPU, we only call build_clear_page()/
    build_copy_page() only once at boot time. Without this patch, programs
    will get random memory corruption (segmentation fault, bus error, etc.)
    while CPU Hotplug (e.g. one CPU is using clear_page() while another is
    generating it in cpu_cache_init()).
    
    For similar reasons we modify build_tlb_refill_handler()'s invocation.
    
    V2:
    1, Rework the code to make CPU#0 can be online/offline.
    2, Introduce cpu_has_local_ebase feature since some types of MIPS CPU
       need a per-CPU tlb_refill_handler().
    Signed-off-by: NHuacai Chen <chenhc@lemote.com>
    Signed-off-by: NHongbing Hu <huhb@lemote.com>
    Acked-by: NDavid Daney <david.daney@cavium.com>
    Patchwork: http://patchwork.linux-mips.org/patch/4994/Acked-by: NJohn Crispin <blogic@openwrt.org>
    8759934e
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