[CCing Tejun and Peter] On Tue 24-11-15 14:50:26, Dmitry Vyukov wrote: > Hello, > > I am hitting the following WARNING on commit > 8005c49d9aea74d382f474ce11afbbc7d7130bec (Nov 15): > > > ------------[ cut here ]------------ > WARNING: CPU: 3 PID: 12661 at include/linux/memcontrol.h:412 > handle_mm_fault+0x17ec/0x3530() > Modules linked in: > CPU: 3 PID: 12661 Comm: executor Tainted: G B W 4.4.0-rc1+ #81 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > 00000000ffffffff ffff88003725fc80 ffffffff825d3336 0000000000000000 > ffff880061d95900 ffffffff84cfb6c0 ffff88003725fcc0 ffffffff81247889 > ffffffff815b68fc ffffffff84cfb6c0 000000000000019c 0000000002f68038 > Call Trace: > [<ffffffff81247ab9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:411 > [<ffffffff815b68fc>] handle_mm_fault+0x17ec/0x3530 mm/memory.c:3440 > [< inline >] access_error arch/x86/mm/fault.c:1020 > [<ffffffff81220951>] __do_page_fault+0x361/0x8b0 arch/x86/mm/fault.c:1227 > [< inline >] trace_page_fault_kernel > ./arch/x86/include/asm/trace/exceptions.h:44 > [< inline >] trace_page_fault_entries arch/x86/mm/fault.c:1314 > [<ffffffff81220f5a>] trace_do_page_fault+0x8a/0x230 arch/x86/mm/fault.c:1330 > [<ffffffff81213f14>] do_async_page_fault+0x14/0x70 > [<ffffffff84bf2b98>] async_page_fault+0x28/0x30 > ---[ end trace 179dec89fcb66e7f ]--- Sasha has reported the same thing some time ago http://www.spinics.net/lists/cgroups/msg14075.html. Tejun had a theory http://www.spinics.net/lists/cgroups/msg14078.html but we never got down to the solution. > Reproduction instructions are somewhat involved. I can provide > detailed instructions if necessary. But maybe we can debug it without > the reproducer. Just in case I've left some traces here: > https://gist.githubusercontent.com/dvyukov/451019c8fb14aa4565a4/raw/4f6d55c19fbec74c5923a1aa62acf1db81fe4e98/gistfile1.txt > > > As a blind guess, I've added the following BUG into copy_process: > > diff --git a/kernel/fork.c b/kernel/fork.c > index b4dc490..c5667e8 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1620,6 +1620,8 @@ static struct task_struct *copy_process(unsigned > long clone_flags, > trace_task_newtask(p, clone_flags); > uprobe_copy_process(p, clone_flags); > > + BUG_ON(p->memcg_may_oom); > + > return p; > > > And it fired: > > ------------[ cut here ]------------ > kernel BUG at kernel/fork.c:1623! > invalid opcode: 0000 [#1] SMP KASAN > Modules linked in: > CPU: 3 PID: 28384 Comm: executor Not tainted 4.4.0-rc1+ #83 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > task: ffff880034c542c0 ti: ffff880033140000 task.ti: ffff880033140000 > RIP: 0010:[<ffffffff81242df3>] [<ffffffff81242df3>] copy_process+0x32e3/0x5bf0 > RSP: 0018:ffff880033147c28 EFLAGS: 00010246 > RAX: ffff880034c542c0 RBX: ffff880033148000 RCX: 0000000000000001 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880060ca9a14 > RBP: ffff880033147e08 R08: ffff880060ca9808 R09: 0000000000000001 > R10: 0000000000000000 R11: 0000000000000001 R12: ffff88006269b148 > R13: 00000000003d0f00 R14: 1ffff10006628fa8 R15: ffff880060ca9640 > FS: 0000000002017880(0063) GS:ffff88006dd00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007fc73b14ae78 CR3: 000000000089a000 CR4: 00000000000006e0 > Stack: > ffffea00017e1780 1ffff10006628f8b ffff880033147c48 ffffffff81338b22 > ffff880034c54a58 ffffffff816509d0 0000000000000246 ffffffff00000001 > ffff880060ca99b8 00007fc73b14ae78 ffffea00017e1780 00000002624ab4d0 > Call Trace: > [<ffffffff81245afd>] _do_fork+0x14d/0xb40 kernel/fork.c:1729 > [< inline >] SYSC_clone kernel/fork.c:1838 > [<ffffffff812465c7>] SyS_clone+0x37/0x50 kernel/fork.c:1832 > [<ffffffff84bf0c76>] entry_SYSCALL_64_fastpath+0x16/0x7a > arch/x86/entry/entry_64.S:185 > Code: 03 0f b6 04 02 48 89 fa 83 e2 07 38 d0 7f 09 84 c0 74 05 e8 c0 > e4 3d 00 41 f6 87 d4 03 00 00 20 0f 84 d7 ce ff ff e8 ed 70 21 00 <0f> > 0b e8 e6 70 21 00 48 8b 1d 8f 39 cf 04 49 bc 00 00 00 00 00 > RIP [<ffffffff81242df3>] copy_process+0x32e3/0x5bf0 > kernel/fork.c:1623 (discriminator 1) > RSP <ffff880033147c28> > ---[ end trace 6b4b09a815461606 ]--- > > > So it seems that copy_process creates tasks with memcg_may_oom flag > set, which looks wrong. Can it be the root cause? > > > Thank you > > -- > 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> -- Michal Hocko SUSE Labs -- 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>