On Tue, Dec 11, 2012 at 02:49:06PM +0800, Xishi Qiu wrote: >>>> Hi Simon, > >>>> >>>> If we use "/sys/devices/system/memory/soft_offline_page" to offline a >>>> free page, the value of mce_bad_pages will be added. Then the page is marked >>>> HWPoison, but it is still managed by page buddy alocator. >>>> >>>> So if we offline it again, the value of mce_bad_pages will be added again. >>>> Assume the page is not allocated during this short time. >>>> >>>> soft_offline_page() >>>> get_any_page() >>>> "else if (is_free_buddy_page(p))" branch return 0 >>>> "goto done"; >>>> "atomic_long_add(1, &mce_bad_pages);" >>>> >>>> I think it would be better to move "if(PageHWPoison(page))" at the beginning of >>>> soft_offline_page(). However I don't know what do these words mean, >>>> "Synchronized using the page lock with memory_failure()" >> >> Hi Xishi, >> >> Unpoison will clear PG_hwpoison flag after hold page lock, memory_failure() and >> soft_offline_page() take the lock to avoid unpoison clear the flag behind them. >> >> Regards, >> Wanpeng Li >> > >Hi Wanpeng, > >As you mean, it is the necessary to get the page lock first when we check the >HWPoison flag every time, this is in order to avoid conflict, right? > Hi Xishi, Avoid race. >So why not use a globe lock here? For example lock_memory_hotplug() is used in >online_pages() and offline_pages()? Just for a single page, a global lock maybe more contend. Regards, Wanpeng Li > >Thanks, >Xishi Qiu -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>