On Fri, Jan 19, 2018 at 04:14:42PM +1300, xen@xxxxxxxxxxxxxxxxxx wrote: > > On 19/01/18 4:04 PM, Matthew Wilcox wrote: > > On Thu, Jan 18, 2018 at 02:18:20PM -0800, Laura Abbott wrote: > > > On 01/18/2018 01:55 PM, Andrew Morton wrote: > > > > > [ 24.647744] BUG: unable to handle kernel NULL pointer dereference at > > > > > 00000008 > > > > > [ 24.647801] IP: __radix_tree_lookup+0x14/0xa0 > > > > > [ 24.647811] *pdpt = 00000000253d6027 *pde = 0000000000000000 > > > > > [ 24.647828] Oops: 0000 [#1] SMP > > > > > [ 24.647842] CPU: 5 PID: 3600 Comm: java Not tainted > > > > > 4.14.13-rh10-20180115190010.xenU.i386 #1 > > > > > [ 24.647855] task: e52518c0 task.stack: e4e7a000 > > > > > [ 24.647866] EIP: __radix_tree_lookup+0x14/0xa0 > > > > > [ 24.647876] EFLAGS: 00010286 CPU: 5 > > > > > [ 24.647884] EAX: 00000004 EBX: 00000007 ECX: 00000000 EDX: 00000000 If my understanding is right, EDX contains the index we're looking up. Which is zero. So the swp_entry we got is one bit away from being NULL. Hmm. Have you run memtest86 or some other memory tester on the system recently? > PS: cannot recall seeing this issue on x86_64, just 32 bit. Laura has 64-bit instances of this. PPS: reminder > this is on a Xen VM which per https://xenbits.xen.org/docs/unstable/man/xl.cfg.5.html#PVH-Guest-Specific-Options > has "out of sync pagetables" if that is relevant (we do not set that option, > I am unsure what default is used). Laura also has non-Xen instances of this. They may not all be the same bug, of course. -- 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>
