Hi, all, I found that the "spawn" program of UnixBench may get segfault/bus error or other memory corruptions when we do CPU hotplug on quad-core Loongson-3. We have debug this for a long time but have no solution, so I want to know whether this is not a Loongson-specific but a MIPS-specific problem. Testbed configuration: Linux kernel-3.6.11 with Loongson-3 patches (the linux-3.6 branch of http://dev.lemote.com/cgit/linux-official.git) UnixBench-5.1.3 (http://code.google.com/p/byte-unixbench/) 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 done -- Test method: 1, run "hotplug.sh" and then run "spawn 10000", spawn will get segfault after a few minutes. 2, run "hotplug.sh" and then run "taskset -c 0 spawn 10000" (spawn runs only on core-0), spawn will get segfault in half an hour. 3, run "taskset -c 0 hotplug.sh" and then run "spawn 10000" (hotplug.sh runs only on core-0), spawn will get segfault in half an hour. 4, run "taskset -c 0 hotplug.sh" and then run "taskset -c 0 spawn 10000" (both spawn and hotplug.sh run only on core-0), spawn will finish successfully after about 3 hours. This looks like the bug fixed in the below commit, but Linux-3.6 already have merged this patch: -- commit 5c200197130e307de6eba72fc335c83c9dd6a5bc Author: Maksim Rayskiy <maksim.rayskiy@xxxxxxxxx> Date: Thu Nov 10 17:59:45 2011 +0000 MIPS: ASID conflict after CPU hotplug -- BTW, we found that if we do build_clear_page()/build_copy_page() in cpu_cache_init() only on Core-0 at the first boot time (Don't do it while CPU Hotplug, and don't do it on Core-1,2,3), the possibility of segfault decreases. Any ideas? Best wishes, Huacai Chen
