Messages in this thread | | | Date | Tue, 2 Jun 2015 14:54:27 +0800 (CST) | From | weiqi <> | Subject | PROBLEM: infinite loop do_sparc64_fault with fault_code 2 |
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Hello, Everyone Nearly, I'm working on a sparc64 machine with linux-2.6.32 (32 cores, SMP) ,64bit kernel and userspace is 32bit. when I run LTP test case with command :"./kill10 -c100 -g 1 -n 1", It will trap in an infinite page_fault loop occasionally. and one of the kill10 process will use 100% CPU . (easy to repeat, just run command again and again)
After some debug, I find :
1) the fault address is the same, and always at kill10's user-stack, for example "0xffb0b470".
2) the fault happend when kill10 handle signal at put_user() , code path: arch/sparc/kernel/signal32.c: setup_frame32() --> put_user().
3) The first fault is handled by do_wp_page() because of COW, and then do_wp_page() found PageAnon(old_page) then reuse old_page.
4) then go into infinite loop fault with fault_code 2 (D-TLB miss), and handled by handle_pte_fault() out at flush_tlb_page() which has a comment : /* * This is needed only for protection faults but the arch code * is not yet telling us if this is a protection fault or not. * This still avoids useless tlb flushes for .text page faults * with threads. */ if (flags & FAULT_FLAG_WRITE) flush_tlb_page(vma, address);
I'v also tested with linux-3.10, and almost same result. I know sparc has software tlb process, In the function do_wp_page(), it will call flush_tlb_page() and update_mmu_cache() , but It seems no effect, just D-TLB miss infinitely at same address
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