On Thu, 20 Dec 2012, Sasha Levin wrote: > On 12/19/2012 08:44 PM, Hugh Dickins wrote: > > The rmap walks in ksm.c are like those in rmap.c: > > they can safely be done with anon_vma_lock_read(). > > > > Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> > > --- > > Hi Hugh, > > This patch didn't fix the ksm oopses I'm seeing. I wouldn't expect it to (and should certainly have mentioned oopses in the commit message if I'd intended): this patch was merely an optimization/clarification of a commit gone in for 3.8-rc1. Understandable misunderstanding: you took my Cc too seriously, I just thought I'd better keep Petr in the loop on current changes to ksm.c, and foolishly kept you in too ;) Your oopses are on linux-next, which as of 20121220 still had Petr's nice but buggy NUMA KSM patch in: it should go away when Stephen gets a fresh mm update from Andrew, then reappear once his v6 goes into mm. To stop these oopses in get_mergeable_page (inlined in unstable_tree_search_insert) you need the patch I showed on Tuesday, which I hope he'll merge in for his v6. That doesn't fix all of the problems, but hopefully all that you'll encounter before I've devised a fix for the separate stale stable_nodes issue. Hugh > > This is with both patches applied: > > > [ 191.221082] BUG: unable to handle kernel NULL pointer dereference at 0000000000000110 > [ 191.226749] IP: [<ffffffff81185bf0>] __lock_acquire+0xb0/0xa90 > [ 191.228437] PGD 1469f067 PUD 1466a067 PMD 0 > [ 191.229185] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC > [ 191.230031] Dumping ftrace buffer: > [ 191.230031] (ftrace buffer empty) > [ 191.230031] CPU 3 > [ 191.230031] Pid: 3174, comm: ksmd Tainted: G W 3.7.0-next-20121220-sasha-00015-g5dc79b2-dirty #223 > [ 191.230031] RIP: 0010:[<ffffffff81185bf0>] [<ffffffff81185bf0>] __lock_acquire+0xb0/0xa90 > [ 191.230031] RSP: 0018:ffff8800be933b78 EFLAGS: 00010046 > [ 191.230031] RAX: 0000000000000086 RBX: 0000000000000110 RCX: 0000000000000001 > [ 191.230031] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000110 > [ 191.230031] RBP: ffff8800be933c18 R08: 0000000000000002 R09: 0000000000000000 > [ 191.230031] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000 > [ 191.230031] R13: 0000000000000002 R14: ffff8800be940000 R15: 0000000000000000 > [ 191.230031] FS: 0000000000000000(0000) GS:ffff88000fc00000(0000) knlGS:0000000000000000 > [ 191.230031] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 191.230031] CR2: 0000000000000110 CR3: 000000001469e000 CR4: 00000000000406e0 > [ 191.230031] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 191.230031] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > [ 191.230031] Process ksmd (pid: 3174, threadinfo ffff8800be932000, task ffff8800be940000) > [ 191.230031] Stack: > [ 191.230031] ffff8800be933fd8 0000000000000000 ffff8800be933bb8 ffffffff810a4ec8 > [ 191.230031] ffff8800be933bc8 ffffffff811572a8 ffff88000fdd78c0 ffff88000fdd78d0 > [ 191.230031] ffff8800be933bc8 ffffffff81077ce5 ffff8800be933bf8 ffffffff81157075 > [ 191.230031] Call Trace: > [ 191.230031] [<ffffffff810a4ec8>] ? kvm_clock_read+0x38/0x70 > [ 191.230031] [<ffffffff811572a8>] ? sched_clock_cpu+0x108/0x120 > [ 191.230031] [<ffffffff81077ce5>] ? sched_clock+0x15/0x20 > [ 191.230031] [<ffffffff81157075>] ? sched_clock_local+0x25/0x90 > [ 191.230031] [<ffffffff81188a3a>] lock_acquire+0x1ca/0x270 > [ 191.230031] [<ffffffff812599cf>] ? unstable_tree_search_insert+0x9f/0x260 > [ 191.230031] [<ffffffff83cd7f27>] down_read+0x47/0x90 > [ 191.230031] [<ffffffff812599cf>] ? unstable_tree_search_insert+0x9f/0x260 > [ 191.230031] [<ffffffff812599cf>] unstable_tree_search_insert+0x9f/0x260 > [ 191.230031] [<ffffffff8125afc7>] cmp_and_merge_page+0xe7/0x1e0 > [ 191.230031] [<ffffffff8125b125>] ksm_do_scan+0x65/0xa0 > [ 191.230031] [<ffffffff8125b1cf>] ksm_scan_thread+0x6f/0x2d0 > [ 191.230031] [<ffffffff8113deb0>] ? abort_exclusive_wait+0xb0/0xb0 > [ 191.230031] [<ffffffff8125b160>] ? ksm_do_scan+0xa0/0xa0 > [ 191.230031] [<ffffffff8113cc43>] kthread+0xe3/0xf0 > [ 191.230031] [<ffffffff8113cb60>] ? __kthread_bind+0x40/0x40 > [ 191.230031] [<ffffffff83cdba7c>] ret_from_fork+0x7c/0xb0 > [ 191.230031] [<ffffffff8113cb60>] ? __kthread_bind+0x40/0x40 > [ 191.230031] Code: 00 83 3d 33 2b b0 05 00 0f 85 d5 09 00 00 be f9 0b 00 00 48 c7 c7 24 d1 b2 84 89 55 88 e8 09 80 f8 ff 8b 55 > 88 e9 b9 09 00 00 90 <48> 81 3b 60 59 22 86 b8 01 00 00 00 44 0f 44 e8 41 83 fc 01 77 > [ 191.230031] RIP [<ffffffff81185bf0>] __lock_acquire+0xb0/0xa90 > [ 191.230031] RSP <ffff8800be933b78> > [ 191.230031] CR2: 0000000000000110 > [ 191.230031] ---[ end trace 55f664bfe0f01693 ]--- > > > Thanks, > Sasha -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>