Re: [Question] race condition in mm/page_alloc.c regarding page->lru?
From: TAO HU
Date: Fri Apr 02 2010 - 01:19:51 EST
Hi, KOSAKI Motohiro
I'm glad to know your're considering patch "mm: Check if any ..."
though it is not my original purpose :)
cc: Arve Hjønnevåg who is the author
On Fri, Apr 2, 2010 at 1:03 PM, KOSAKI Motohiro
<kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
> Cc to Mel,
>
>> 2 patches related to page_alloc.c were applied.
>> Does anyone see a connection between the 2 patches and the panic?
>> NOTE: the full patches are attached.
>
> I think your attached two patches are perfectly unrelated your problem.
>
> "mm: Add min_free_order_shift tunable." seems makes zero sense. I don't think this patch
> need to be merge.
>
> but "mm: Check if any page in a pageblock is reserved before marking it MIGRATE_RESERVE"
> treat strange hardware correctly, I think. If Mel ack this, I hope merge it.
> Mel, Can we hear your opinion?
>
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index a596bfd..34a29e2 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -2551,6 +2551,20 @@ static inline unsigned long
>> wait_table_bits(unsigned long size)
>> #define LONG_ALIGN(x) (((x)+(sizeof(long))-1)&~((sizeof(long))-1))
>>
>> /*
>> + * Check if a pageblock contains reserved pages
>> + */
>> +static int pageblock_is_reserved(unsigned long start_pfn)
>> +{
>> + unsigned long end_pfn = start_pfn + pageblock_nr_pages;
>> + unsigned long pfn;
>> +
>> + for (pfn = start_pfn; pfn < end_pfn; pfn++)
>> + if (PageReserved(pfn_to_page(pfn)))
>> + return 1;
>> + return 0;
>> +}
>> +
>> +/*
>> * Mark a number of pageblocks as MIGRATE_RESERVE. The number
>> * of blocks reserved is based on zone->pages_min. The memory within the
>> * reserve will tend to store contiguous free pages. Setting min_free_kbytes
>> @@ -2579,7 +2593,7 @@ static void setup_zone_migrate_reserve(struct zone *zone)
>> continue;
>>
>> /* Blocks with reserved pages will never free, skip them. */
>> - if (PageReserved(page))
>> + if (pageblock_is_reserved(pfn))
>> continue;
>>
>> block_migratetype = get_pageblock_migratetype(page);
>> --
>> 1.5.4.3
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 5c44ed4..a596bfd 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -119,6 +119,7 @@ static char * const zone_names[MAX_NR_ZONES] = {
>> };
>>
>> int min_free_kbytes = 1024;
>> +int min_free_order_shift = 1;
>>
>> unsigned long __meminitdata nr_kernel_pages;
>> unsigned long __meminitdata nr_all_pages;
>> @@ -1256,7 +1257,7 @@ int zone_watermark_ok(struct zone *z, int order,
>> unsigned long mark,
>> free_pages -= z->free_area[o].nr_free << o;
>>
>> /* Require fewer higher order pages to be free */
>> - min >>= 1;
>> + min >>= min_free_order_shift;
>>
>> if (free_pages <= min)
>> return 0;
>> --
>>
>>
>> On Thu, Apr 1, 2010 at 12:05 PM, TAO HU <tghk48@xxxxxxxxxxxx> wrote:
>> > Hi, all
>> >
>> > We got a panic on our ARM (OMAP) based HW.
>> > Our code is based on 2.6.29 kernel (last commit for mm/page_alloc.c is
>> > cc2559bccc72767cb446f79b071d96c30c26439b)
>> >
>> > It appears to crash while going through pcp->list in
>> > buffered_rmqueue() of mm/page_alloc.c after checking vmlinux.
>> > "00100100" implies LIST_POISON1 that suggests a race condition between
>> > list_add() and list_del() in my personal view.
>> > However we not yet figure out locking problem regarding page.lru.
>> >
>> > Any known issues about race condition in mm/page_alloc.c?
>> > And other hints are highly appreciated.
>> >
>> > /* Find a page of the appropriate migrate type */
>> > if (cold) {
>> > ... ...
>> > } else {
>> > list_for_each_entry(page, &pcp->list, lru)
>> > if (page_private(page) == migratetype)
>> > break;
>> > }
>> >
>> > <1>[120898.805267] Unable to handle kernel paging request at virtual
>> > address 00100100
>> > <1>[120898.805633] pgd = c1560000
>> > <1>[120898.805786] [00100100] *pgd=897b3031, *pte=00000000, *ppte=00000000
>> > <4>[120898.806457] Internal error: Oops: 17 [#1] PREEMPT
>> > ... ...
>> > <4>[120898.807861] CPU: 0 Not tainted (2.6.29-omap1 #1)
>> > <4>[120898.808044] PC is at get_page_from_freelist+0x1d0/0x4b0
>> > <4>[120898.808227] LR is at get_page_from_freelist+0xc8/0x4b0
>> > <4>[120898.808563] pc : [<c00a600c>] lr : [<c00a5f04>] psr: 800000d3
>> > <4>[120898.808563] sp : c49fbd18 ip : 00000000 fp : c49fbd74
>> > <4>[120898.809020] r10: 00000000 r9 : 001000e8 r8 : 00000002
>> > <4>[120898.809204] r7 : 001200d2 r6 : 60000053 r5 : c0507c4c r4 : c49fa000
>> > <4>[120898.809509] r3 : 001000e8 r2 : 00100100 r1 : c0507c6c r0 : 00000001
>> > <4>[120898.809844] Flags: Nzcv IRQs off FIQs off Mode SVC_32 ISA
>> > ARM Segment kernel
>> > <4>[120898.810028] Control: 10c5387d Table: 82160019 DAC: 00000017
>> > <4>[120898.948425] Backtrace:
>> > <4>[120898.948760] [<c00a5e3c>] (get_page_from_freelist+0x0/0x4b0)
>> > from [<c00a6398>] (__alloc_pages_internal+0xac/0x3e8)
>> > <4>[120898.949554] [<c00a62ec>] (__alloc_pages_internal+0x0/0x3e8)
>> > from [<c00b461c>] (handle_mm_fault+0x16c/0xbac)
>> > <4>[120898.950347] [<c00b44b0>] (handle_mm_fault+0x0/0xbac) from
>> > [<c00b51d0>] (__get_user_pages+0x174/0x2b4)
>> > <4>[120898.951019] [<c00b505c>] (__get_user_pages+0x0/0x2b4) from
>> > [<c00b534c>] (get_user_pages+0x3c/0x44)
>> > <4>[120898.951812] [<c00b5310>] (get_user_pages+0x0/0x44) from
>> > [<c00caf9c>] (get_arg_page+0x50/0xa4)
>> > <4>[120898.952636] [<c00caf4c>] (get_arg_page+0x0/0xa4) from
>> > [<c00cb1ec>] (copy_strings+0x108/0x210)
>> > <4>[120898.953430] r7:beffffe4 r6:00000ffc r5:00000000 r4:00000018
>> > <4>[120898.954223] [<c00cb0e4>] (copy_strings+0x0/0x210) from
>> > [<c00cb330>] (copy_strings_kernel+0x3c/0x74)
>> > <4>[120898.955047] [<c00cb2f4>] (copy_strings_kernel+0x0/0x74) from
>> > [<c00cc778>] (do_execve+0x18c/0x2b0)
>> > <4>[120898.955841] r5:0001e240 r4:0001e224
>> > <4>[120898.956329] [<c00cc5ec>] (do_execve+0x0/0x2b0) from
>> > [<c00400e4>] (sys_execve+0x3c/0x5c)
>> > <4>[120898.957153] [<c00400a8>] (sys_execve+0x0/0x5c) from
>> > [<c003ce80>] (ret_fast_syscall+0x0/0x2c)
>> > <4>[120898.957946] r7:0000000b r6:0001e270 r5:00000000 r4:0001d580
>> > <4>[120898.958740] Code: e1530008 0a000006 e2429018 e1a03009 (e5b32018)
>> >
>> >
>> >
>> > --
>> > Best Regards
>> > Hu Tao
>> >
>
>
>
>
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