Messages in this thread | | | Date | Thu, 20 Mar 2014 21:53:36 -0400 | From | Sasha Levin <> | Subject | Re: kernel BUG in munlock_vma_pages_range |
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On 12/13/2013 04:08 AM, Vlastimil Babka wrote: > On 12/13/2013 09:49 AM, Bob Liu wrote: >> On 12/13/2013 05:05 AM, Sasha Levin wrote: >>> On 12/12/2013 07:41 AM, Vlastimil Babka wrote: >>>> On 12/12/2013 06:03 AM, Bob Liu wrote: >>>>> >>>>> On 12/12/2013 11:16 AM, Sasha Levin wrote: >>>>>> On 12/11/2013 05:59 PM, Vlastimil Babka wrote: >>>>>>> On 12/09/2013 09:26 PM, Sasha Levin wrote: >>>>>>>> On 12/09/2013 12:12 PM, Vlastimil Babka wrote: >>>>>>>>> On 12/09/2013 06:05 PM, Sasha Levin wrote: >>>>>>>>>> On 12/09/2013 04:34 AM, Vlastimil Babka wrote: >>>>>>>>>>> Hello, I will look at it, thanks. >>>>>>>>>>> Do you have specific reproduction instructions? >>>>>>>>>> >>>>>>>>>> Not really, the fuzzer hit it once and I've been unable to trigger >>>>>>>>>> it again. Looking at >>>>>>>>>> the piece of code involved it might have had something to do with >>>>>>>>>> hugetlbfs, so I'll crank >>>>>>>>>> up testing on that part. >>>>>>>>> >>>>>>>>> Thanks. Do you have trinity log and the .config file? I'm currently >>>>>>>>> unable to even boot linux-next >>>>>>>>> with my config/setup due to a GPF. >>>>>>>>> Looking at code I wouldn't expect that it could encounter a tail >>>>>>>>> page, without first encountering a >>>>>>>>> head page and skipping the whole huge page. At least in THP case, as >>>>>>>>> TLB pages should be split when >>>>>>>>> a vma is split. As for hugetlbfs, it should be skipped for >>>>>>>>> mlock/munlock operations completely. One >>>>>>>>> of these assumptions is probably failing here... >>>>>>>> >>>>>>>> If it helps, I've added a dump_page() in case we hit a tail page >>>>>>>> there and got: >>>>>>>> >>>>>>>> [ 980.172299] page:ffffea003e5e8040 count:0 mapcount:1 >>>>>>>> mapping: (null) index:0 >>>>>>>> x0 >>>>>>>> [ 980.173412] page flags: 0x2fffff80008000(tail) >>>>>>>> >>>>>>>> I can also add anything else in there to get other debug output if >>>>>>>> you think of something else useful. >>>>>>> >>>>>>> Please try the following. Thanks in advance. >>>>>> >>>>>> [ 428.499889] page:ffffea003e5c0040 count:0 mapcount:4 >>>>>> mapping: (null) index:0x0 >>>>>> [ 428.499889] page flags: 0x2fffff80008000(tail) >>>>>> [ 428.499889] start=140117131923456 pfn=16347137 >>>>>> orig_start=140117130543104 page_increm >>>>>> =1 vm_start=140117130543104 vm_end=140117134688256 vm_flags=135266419 >>>>>> [ 428.499889] first_page pfn=16347136 >>>>>> [ 428.499889] page:ffffea003e5c0000 count:204 mapcount:44 >>>>>> mapping:ffff880fb5c466c1 inde >>>>>> x:0x7f6f8fe00 >>>>>> [ 428.499889] page flags: >>>>>> 0x2fffff80084068(uptodate|lru|active|head|swapbacked) >>>>> >>>>> From this print, it looks like the page is still a huge page. >>>>> One situation I guess is a huge page which isn't PageMlocked and passed >>>>> to munlock_vma_page(). I'm not sure whether this will happen. >>>> >>>> Yes that's quite likely the case. It's not illegal to happen I would say. >>>> >>>>> Please take a try this patch. >>>> >>>> I've made a simpler version that does away with the ugly page_mask >>>> thing completely. >>>> Please try that as well. Thanks. >>>> >>>> Also when working on this I think I found another potential but much >>>> rare problem >>>> when munlock_vma_page races with a THP split. That would however >>>> manifest such that >>>> part of the former tail pages would stay PageMlocked. But that still >>>> needs more thought. >>>> The bug at hand should however be fixed by this patch. >>> >>> Yup, this patch seems to fix the issue previously reported. >>> >>> However, I'll piggyback another thing that popped up now that the vm >>> could run for a while which >>> also seems to be caused by the original patch. It looks like a pretty >>> straightforward deadlock, but > > Sigh, put one down, patch it around... :) > >> Looks like put_page() in __munlock_pagevec() need to get the >> zone->lru_lock which is already held when entering __munlock_pagevec(). > > I've come to the same conclusion, however: > >> How about fix like this? > > That unfortunately removes most of the purpose of this function which was to avoid repeated locking. > > Please try this patch.
It seems that this one is back, not exactly sure why yet:
[ 2857.034927] kernel BUG at include/linux/page-flags.h:415! [ 2857.035576] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 2857.036702] Dumping ftrace buffer: [ 2857.037447] (ftrace buffer empty) [ 2857.037937] Modules linked in: [ 2857.038379] CPU: 25 PID: 21381 Comm: trinity-c61 Tainted: G W 3.14.0-rc7-next-20140320-sasha-00015-gd752393-dirty #261 [ 2857.039854] task: ffff88080f91b000 ti: ffff8807fd106000 task.ti: ffff8807fd106000 [ 2857.040328] RIP: 0010:[<ffffffff8129dc93>] [<ffffffff8129dc93>] munlock_vma_pages_range+0x93/0x1d0 [ 2857.040328] RSP: 0000:ffff8807fd107e08 EFLAGS: 00010246 [ 2857.040328] RAX: ffff88052c955360 RBX: 0000000041b36000 RCX: 000000000000009f [ 2857.040328] RDX: 0000000000000000 RSI: ffff88080f91bcf0 RDI: 0000000004fd5360 [ 2857.040328] RBP: ffff8807fd107ec8 R08: 0000000000000001 R09: 0000000000000000 [ 2857.040328] R10: 0000000000000001 R11: 0000000000000001 R12: ffffea0013f54d80 [ 2857.040328] R13: ffff88068083c200 R14: 0000000041b37000 R15: ffff8807fd107e94 [ 2857.040328] FS: 00007fcd4bd02700(0000) GS:ffff8806acc00000(0000) knlGS:0000000000000000 [ 2857.040328] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 2857.040328] CR2: 00000000027405a8 CR3: 0000000804ad4000 CR4: 00000000000006a0 [ 2857.040328] DR0: 0000000000698000 DR1: 0000000000698000 DR2: 0000000000000000 [ 2857.040328] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 [ 2857.040328] Stack: [ 2857.040328] 0000000000000000 0000000000000000 00018807fd107e38 0000000000000000 [ 2857.040328] 0000000000000000 ffff88068083c200 00000000fd107e88 0000000000000000 [ 2857.040328] 00ff8807fd107e58 ffff88052be99b20 ffff8807fd107eb8 ffff88068083c200 [ 2857.040328] Call Trace: [ 2857.040328] [<ffffffff812a1462>] do_munmap+0x1d2/0x360 [ 2857.040328] [<ffffffff844bce16>] ? down_write+0xa6/0xc0 [ 2857.040328] [<ffffffff812a1636>] ? vm_munmap+0x46/0x80 [ 2857.040328] [<ffffffff812a1644>] vm_munmap+0x54/0x80 [ 2857.040328] [<ffffffff812a169c>] SyS_munmap+0x2c/0x40 [ 2857.040328] [<ffffffff844c9210>] tracesys+0xdd/0xe2 [ 2857.040328] Code: ff 49 89 c4 48 85 c0 0f 84 f3 00 00 00 48 3d 00 f0 ff ff 0f 87 e7 00 00 00 48 8b 00 66 85 c0 79 17 31 f6 4c 89 e7 e8 fd d0 fc ff <0f> 0b 0f 1f 00 eb fe 66 0f 1f 44 00 00 49 8b 04 24 f6 c4 40 74 [ 2857.062774] RIP [<ffffffff8129dc93>] munlock_vma_pages_range+0x93/0x1d0 [ 2857.062774] RSP <ffff8807fd107e08>
Thanks, Sasha
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