Messages in this thread Patch in this message | | | Date | Sun, 12 Jan 2003 03:31:20 +0100 (MET) | From | Mikael Pettersson <> | Subject | 2.5.55/.56 instant reboot problem on 486 |
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My '94 vintage 486 has problems booting 2.5.55 and 2.5.56. When it fails, the boot gets to loading the kernel and printing "Ok, booting the kernel.". Then there is a short pause (line a tenth of a second) and the machine reboots.
After doing a binary search with "for(;;);" statements (printk doesn't work this early) I found that the reboot occurs in arch/i386/mm/init.c:kernel_physical_mapping_init(): (start_kernel() -> setup_arch() -> paging_init() -> pagetable_init() -> kernel_physical_mapping_init())
diff -ruNp linux-2.5.55/arch/i386/mm/init.c linux-2.5.55.hack/arch/i386/mm/init.c --- linux-2.5.55/arch/i386/mm/init.c 2003-01-12 02:20:49.000000000 +0100 +++ linux-2.5.55.hack/arch/i386/mm/init.c 2003-01-12 01:44:49.000000000 +0100 @@ -134,6 +134,7 @@ static void __init kernel_physical_mappi pgd = pgd_base + pgd_ofs; pfn = 0; + //for(;;); for (; pgd_ofs < PTRS_PER_PGD; pgd++, pgd_ofs++) { pmd = one_md_table_init(pgd); if (pfn >= max_low_pfn) @@ -151,6 +152,7 @@ static void __init kernel_physical_mappi } } } + for(;;); } static inline int page_kills_ppro(unsigned long pagenr) If I uncomment the first "//for(;;);" the kernel hangs, but if I keep it commented out, the kernel reboots -- i.e. it doesn't get to the final "for(;;);" at the end of the function. The problem is apparently related to the size of the kernel. With gcc-2.95.3 and my normal config for this machine, size vmlinux is
text data bss dec hex filename 1330953 109008 125656 1565617 17e3b1 vmlinux
and the kernel reboots. If I alter the size by changing some irrelevant config option (like disabling INPUT_MOUSEDEV or enabling KALLSYMS), the reboot problem doesn't occur.
With gcc-3.2 the bug disappears, but only because gcc-3.2 generates a much larger code segment. If I remove some driver & fs config options, the vmlinux size becomes almost the same as above, and the reboot bug appears again.
The same kernel that fails on the 486 boots Ok on my newer test boxes, so the problem is either 486-specific, related to the actual memory size, or the BIOS memory size reporting method (the 486 uses int 15 0x88); here's what 2.5.54 says:
BIOS-provided physical RAM map: BIOS-88: 0000000000000000 - 000000000009f000 (usable) BIOS-88: 0000000000100000 - 0000000001c00000 (usable) The 486 has no known HW problems, and it survives memtest86.
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