Messages in this thread Patch in this message | | | From | Kevin Cernekee <> | Date | Mon, 6 Sep 2010 21:03:48 -0700 | Subject | [PATCH RESEND 3/5] MIPS: pfn_valid() is broken on low memory HIGHMEM systems |
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pfn_valid() compares the PFN to max_mapnr:
__pfn >= min_low_pfn && __pfn < max_mapnr;
On HIGHMEM kernels, highend_pfn is used to set the value of max_mapnr. Unfortunately, highend_pfn is left at zero if the system does not actually have enough RAM to reach into the HIGHMEM range. This causes pfn_valid() to always return false, and when debug checks are enabled the kernel will fail catastrophically:
Memory: 22432k/32768k available (2249k kernel code, 10336k reserved, 653k data, 1352k init, 0k highmem) NR_IRQS:128 kfree_debugcheck: out of range ptr 81c02900h. Kernel bug detected[#1]: Cpu 0 $ 0 : 00000000 10008400 00000034 00000000 $ 4 : 8003e160 802a0000 8003e160 00000000 $ 8 : 00000000 0000003e 00000747 00000747 ...
On such a configuration, max_low_pfn should be used to set max_mapnr.
This was seen on 2.6.34.
Signed-off-by: Kevin Cernekee <cernekee@gmail.com> --- arch/mips/mm/init.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c index 2efcbd2..18183a4 100644 --- a/arch/mips/mm/init.c +++ b/arch/mips/mm/init.c @@ -370,7 +370,7 @@ void __init mem_init(void) #ifdef CONFIG_DISCONTIGMEM #error "CONFIG_HIGHMEM and CONFIG_DISCONTIGMEM dont work together yet" #endif - max_mapnr = highend_pfn; + max_mapnr = highend_pfn ? : max_low_pfn; #else max_mapnr = max_low_pfn; #endif -- 1.7.0.4
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