race condition in mm/page_alloc.c regarding page->lru?
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From: TAO HU on 2 Apr 2010 03:10 Hi, kamezawa hiroyu Thanks for the hint! Hi, Minchan Kim Sorry. Not exactly sure your idea about <grep "page handling">. Below is a result of $ grep -n -r "list_del(&page->lru)" * in our src tree arch/s390/mm/pgtable.c:83: list_del(&page->lru); arch/s390/mm/pgtable.c:226: list_del(&page->lru); arch/x86/mm/pgtable.c:60: list_del(&page->lru); drivers/xen/balloon.c:154: list_del(&page->lru); drivers/virtio/virtio_balloon.c:143: list_del(&page->lru); fs/cifs/file.c:1780: list_del(&page->lru); fs/btrfs/extent_io.c:2584: list_del(&page->lru); fs/mpage.c:388: list_del(&page->lru); include/linux/mm_inline.h:37: list_del(&page->lru); include/linux/mm_inline.h:47: list_del(&page->lru); kernel/kexec.c:391: list_del(&page->lru); kernel/kexec.c:711: list_del(&page->lru); mm/migrate.c:69: list_del(&page->lru); mm/migrate.c:695: list_del(&page->lru); mm/hugetlb.c:467: list_del(&page->lru); mm/hugetlb.c:509: list_del(&page->lru); mm/hugetlb.c:836: list_del(&page->lru); mm/hugetlb.c:844: list_del(&page->lru); mm/hugetlb.c:900: list_del(&page->lru); mm/hugetlb.c:1130: list_del(&page->lru); mm/hugetlb.c:1809: list_del(&page->lru); mm/vmscan.c:597: list_del(&page->lru); mm/vmscan.c:1148: list_del(&page->lru); mm/vmscan.c:1246: list_del(&page->lru); mm/slub.c:827: list_del(&page->lru); mm/slub.c:1249: list_del(&page->lru); mm/slub.c:1263: list_del(&page->lru); mm/slub.c:2419: list_del(&page->lru); mm/slub.c:2809: list_del(&page->lru); mm/readahead.c:65: list_del(&page->lru); mm/readahead.c:100: list_del(&page->lru); mm/page_alloc.c:532: list_del(&page->lru); mm/page_alloc.c:679: list_del(&page->lru); mm/page_alloc.c:741: list_del(&page->lru); mm/page_alloc.c:820: list_del(&page->lru); mm/page_alloc.c:1107: list_del(&page->lru); mm/page_alloc.c:4784: list_del(&page->lru); On Fri, Apr 2, 2010 at 1:15 PM, Minchan Kim <minchan.kim(a)gmail.com> wrote: > On Fri, Apr 2, 2010 at 2:04 PM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu(a)jp.fujitsu.com> wrote: >> On Fri, 2 Apr 2010 11:51:33 +0800 >> TAO HU <tghk48(a)motorola.com> wrote: >> >>> 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 don't think there are relationship between patches and your panic. >> >> BTW, there is other case about the backlog rather than race in alloc_pages() >> itself. If someone list_del(&page->lru) and the page is already freed, >> you'll see the same backlog later. >> Then, I doubt use-after-free case rather than complicated races. > > It does make sense. > Please, grep "page handling" by out-of-mainline code. > If you found out, Please, post it. > > -- > Kind regards, > Minchan Kim > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Minchan Kim on 2 Apr 2010 03:30 On Fri, Apr 2, 2010 at 4:00 PM, TAO HU <tghk48(a)motorola.com> wrote: > Hi, kamezawa hiroyu > > Thanks for the hint! > > Hi, Minchan Kim > > Sorry. Not exactly sure your idea about <grep "page handling">. > Below is a result of $ grep -n -r "list_del(&page->lru)" * in our src tree It's not enough. Maybe you have to review your's patches based on mainline. > > arch/s390/mm/pgtable.c:83: list_del(&page->lru); > arch/s390/mm/pgtable.c:226: list_del(&page->lru); > arch/x86/mm/pgtable.c:60: list_del(&page->lru); > drivers/xen/balloon.c:154: list_del(&page->lru); > drivers/virtio/virtio_balloon.c:143: list_del(&page->lru); > fs/cifs/file.c:1780: list_del(&page->lru); > fs/btrfs/extent_io.c:2584: list_del(&page->lru); > fs/mpage.c:388: list_del(&page->lru); > include/linux/mm_inline.h:37: list_del(&page->lru); > include/linux/mm_inline.h:47: list_del(&page->lru); > kernel/kexec.c:391: list_del(&page->lru); > kernel/kexec.c:711: list_del(&page->lru); > mm/migrate.c:69: list_del(&page->lru); > mm/migrate.c:695: list_del(&page->lru); > mm/hugetlb.c:467: list_del(&page->lru); > mm/hugetlb.c:509: list_del(&page->lru); > mm/hugetlb.c:836: list_del(&page->lru); > mm/hugetlb.c:844: list_del(&page->lru); > mm/hugetlb.c:900: list_del(&page->lru); > mm/hugetlb.c:1130: list_del(&page->lru); > mm/hugetlb.c:1809: list_del(&page->lru); > mm/vmscan.c:597: list_del(&page->lru); > mm/vmscan.c:1148: list_del(&page->lru); > mm/vmscan.c:1246: list_del(&page->lru); > mm/slub.c:827: list_del(&page->lru); > mm/slub.c:1249: list_del(&page->lru); > mm/slub.c:1263: list_del(&page->lru); > mm/slub.c:2419: list_del(&page->lru); > mm/slub.c:2809: list_del(&page->lru); > mm/readahead.c:65: list_del(&page->lru); > mm/readahead.c:100: list_del(&page->lru); > mm/page_alloc.c:532: list_del(&page->lru); > mm/page_alloc.c:679: list_del(&page->lru); > mm/page_alloc.c:741: list_del(&page->lru); > mm/page_alloc.c:820: list_del(&page->lru); > mm/page_alloc.c:1107: list_del(&page->lru); > mm/page_alloc.c:4784: list_del(&page->lru); > There are normal caller. I expected some bogus driver of out-of-mainline uses page directly without enough review. Is your kernel working well except this bug? Do you see same oops call trace(about page-allocator) whenever kernel panic happens? I mean if something not page-allocadtor breaks memory, you can see other symptoms. so we can doubt others(H/W, other subsystem). -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Arve Hjønnevåg on 2 Apr 2010 21:00 On Fri, Apr 2, 2010 at 2:48 AM, Mel Gorman <mel(a)csn.ul.ie> wrote: > On Fri, Apr 02, 2010 at 02:03:23PM +0900, KOSAKI Motohiro 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. >> > > Agreed. It's unlikely that there is a race as such in the page > allocator. In buffered_rmqueue that you initially talk about, the lists > being manipulated are per-cpu lists. About the only way to corrupt them > is if you had a NMI hander that called the page allocator. I really hope > your platform is not doing anything like that. > > A double free of page->lru is a possibility. You could try reproducing > the problem with CONFIG_DEBUG_LIST enabled to see if anything falls out. > >> "mm: Add min_free_order_shift tunable." seems makes zero sense. I don't think this patch >> need to be merge. >> > > It makes a marginal amount of sense. Basically what it does is allowing > high-order allocations to go much further below their watermarks than is > currently allowed. If the platform in question is doing a lot of high-order > allocations, this patch could be seen to "fix" the problem but you wouldn't > touch mainline with it with a barge pole. It would be more stable to fix > the drivers to not use high order allocations or use a mempool. > The high order allocation that caused problems was the first level page table for each process. Each time a new process started the kernel would empty the entire page cache to create contiguous free memory. With the reserved pageblock mostly full (fixed by the second patch) this contiguous memory would then almost immediately get used for low order allocations, so the same problem starts again when the next process starts. I agree this patch does not fix the problem, but it does improve things when the problem hits. I have not seen a device in this situation with the second patch applied, but I did not remove the first patch in case the reserved pageblock fills up. > It is inconceivable this patch is related to the problem though. > >> 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? >> > > This patch is interesting and I am surprised it is required. Is it really the > case that page blocks near the start of a zone are dominated with PageReserved > pages but the first one happen to be free? I guess it's conceivable on ARM > where memmap can be freed at boot time. I think this happens by default on arm. The kernel starts at offset 0x8000 to leave room for boot parameters, and in recent kernel versions (>~2.6.26-29) this memory is freed. > > There is a theoritical problem with the patch but it is easily resolved. > A PFN walker like this must call pfn_valid_within() before calling > pfn_to_page(). If they do not, it's possible to get complete garbage > for the page and result in a bad dereference. In this particular case, > it would be a kernel oops rather than memory corruption though. > > If that was fixed, I'd see no problem with Acking the patch. > I can fix this if you want the patch in mainline. I was not sure it was acceptable since will slow down boot on all systems, even where it is not needed. > It is also inconceivable this patch is related to the problem. > >> > >> > 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(a)motorola.com> 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 >> > > >> >> >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo(a)kvack.org. �For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: <a href=mailto:"dont(a)kvack.org"> email(a)kvack.org </a> >> > > -- > Mel Gorman > Part-time Phd Student � � � � � � � � � � � � �Linux Technology Center > University of Limerick � � � � � � � � � � � � IBM Dublin Software Lab > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo(a)vger.kernel.org > More majordomo info at �http://vger.kernel.org/majordomo-info.html > Please read the FAQ at �http://www.tux.org/lkml/ > -- Arve Hj�nnev�g -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: KOSAKI Motohiro on 4 Apr 2010 18:50 Hi > >> "mm: Add min_free_order_shift tunable." seems makes zero sense. I don't think this patch > >> need to be merge. > > > > It makes a marginal amount of sense. Basically what it does is allowing > > high-order allocations to go much further below their watermarks than is > > currently allowed. If the platform in question is doing a lot of high-order > > allocations, this patch could be seen to "fix" the problem but you wouldn't > > touch mainline with it with a barge pole. It would be more stable to fix > > the drivers to not use high order allocations or use a mempool. > > The high order allocation that caused problems was the first level > page table for each process. Each time a new process started the > kernel would empty the entire page cache to create contiguous free > memory. With the reserved pageblock mostly full (fixed by the second > patch) this contiguous memory would then almost immediately get used > for low order allocations, so the same problem starts again when the > next process starts. I agree this patch does not fix the problem, but > it does improve things when the problem hits. I have not seen a device > in this situation with the second patch applied, but I did not remove > the first patch in case the reserved pageblock fills up. I would like to merge the second patch at first. If the same problem still occur, please post bug report. (and please cc arm folks if it is arm pagetable related) > > It is inconceivable this patch is related to the problem though. > > > >> 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? > >> > > > > This patch is interesting and I am surprised it is required. Is it really the > > case that page blocks near the start of a zone are dominated with PageReserved > > pages but the first one happen to be free? I guess it's conceivable on ARM > > where memmap can be freed at boot time. > > I think this happens by default on arm. The kernel starts at offset > 0x8000 to leave room for boot parameters, and in recent kernel > versions (>~2.6.26-29) this memory is freed. > > > > > There is a theoritical problem with the patch but it is easily resolved. > > A PFN walker like this must call pfn_valid_within() before calling > > pfn_to_page(). If they do not, it's possible to get complete garbage > > for the page and result in a bad dereference. In this particular case, > > it would be a kernel oops rather than memory corruption though. > > > > If that was fixed, I'd see no problem with Acking the patch. > > > > I can fix this if you want the patch in mainline. I was not sure it > was acceptable since will slow down boot on all systems, even where it > is not needed. bootup code is not fast path. then, small slowdown is ok, I think. So, I'm looking for your new version patch. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Minchan Kim on 5 Apr 2010 06:50
Hi, Mel and Arve. On Mon, Apr 5, 2010 at 7:14 PM, Mel Gorman <mel(a)csn.ul.ie> wrote: > On Fri, Apr 02, 2010 at 05:59:00PM -0700, Arve Hj?nnev?g wrote: >> On Fri, Apr 2, 2010 at 2:48 AM, Mel Gorman <mel(a)csn.ul.ie> wrote: >> > On Fri, Apr 02, 2010 at 02:03:23PM +0900, KOSAKI Motohiro 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. >> >> >> > >> > Agreed. It's unlikely that there is a race as such in the page >> > allocator. In buffered_rmqueue that you initially talk about, the lists >> > being manipulated are per-cpu lists. About the only way to corrupt them >> > is if you had a NMI hander that called the page allocator. I really hope >> > your platform is not doing anything like that. >> > >> > A double free of page->lru is a possibility. You could try reproducing >> > the problem with CONFIG_DEBUG_LIST enabled to see if anything falls out. >> > >> >> "mm: Add min_free_order_shift tunable." seems makes zero sense. I don't think this patch >> >> need to be merge. >> >> >> > >> > It makes a marginal amount of sense. Basically what it does is allowing >> > high-order allocations to go much further below their watermarks than is >> > currently allowed. If the platform in question is doing a lot of high-order >> > allocations, this patch could be seen to "fix" the problem but you wouldn't >> > touch mainline with it with a barge pole. It would be more stable to fix >> > the drivers to not use high order allocations or use a mempool. >> > >> >> The high order allocation that caused problems was the first level >> page table for each process. > > Out of curiousity, how big is that allocation? Is it specific to > android? If it is, I guess it can be let slide but if it's common, it It is the specific on ARM. You can refer get_pgd_slow in arch/arm/mm/pgd.c. It allocates order 2 page for pgd. > would be worth thinking of an arch-hook that tells the VM that a > particular high-order is very common. For example, one possibility would > be to ask kswapd to always reclaim at a given order even if the > watermarks required are for a lower order. Just out of curiosity, too. Normally, embedded system don't have fork-bomb workload. But I think android's case is some different. That's because Dalvik(JVM) keeps many memory which are anon pages for byte codes by itself as possible as. So system always doesn't have enough memory. In addition, most of embedded system don't have swap. It makes system worse, too. So current reclaimer can't be work well. I am not sure my assumption. Arve, my guessing is right? If it is so, Dalvik have to solve this problem? For example, AFAIK, android kernel has low memory killer. If kernel signals memory pressure, Dalvik have to discard some anon pages which has byte codes for executable. It is just my guessing about android. If I misunderstood about android, please, correct me. :) > >> Each time a new process started the >> kernel would empty the entire page cache to create contiguous free >> memory. > > I ask because I'm surprised the entire page cache got chucked out Maybe it was because system has lots of anon pages but no swap. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |