[+cc akpm, linux-mm, linux-pci] On Wed, Jun 6, 2018 at 10:44 AM Will Deacon <will.deacon@xxxxxxx> wrote: > > On Thu, May 31, 2018 at 08:14:38PM +0800, Xie XiuQi wrote: > > A numa system may return node which is not online. > > For example, a numa node: > > 1) without memory > > 2) NR_CPUS is very small, and the cpus on the node are not brought up > > > > In this situation, we use NUMA_NO_NODE to avoid oops. > > > > [ 25.732905] Unable to handle kernel NULL pointer dereference at virtual address 00001988 > > [ 25.740982] Mem abort info: > > [ 25.743762] ESR = 0x96000005 > > [ 25.746803] Exception class = DABT (current EL), IL = 32 bits > > [ 25.752711] SET = 0, FnV = 0 > > [ 25.755751] EA = 0, S1PTW = 0 > > [ 25.758878] Data abort info: > > [ 25.761745] ISV = 0, ISS = 0x00000005 > > [ 25.765568] CM = 0, WnR = 0 > > [ 25.768521] [0000000000001988] user address but active_mm is swapper > > [ 25.774861] Internal error: Oops: 96000005 [#1] SMP > > [ 25.779724] Modules linked in: > > [ 25.782768] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.17.0-rc6-mpam+ #115 > > [ 25.789714] Hardware name: Huawei D06/D06, BIOS Hisilicon D06 EC UEFI Nemo 2.0 RC0 - B305 05/28/2018 > > [ 25.798831] pstate: 80c00009 (Nzcv daif +PAN +UAO) > > [ 25.803612] pc : __alloc_pages_nodemask+0xf0/0xe70 > > [ 25.808389] lr : __alloc_pages_nodemask+0x184/0xe70 > > [ 25.813252] sp : ffff00000996f660 > > [ 25.816553] x29: ffff00000996f660 x28: 0000000000000000 > > [ 25.821852] x27: 00000000014012c0 x26: 0000000000000000 > > [ 25.827150] x25: 0000000000000003 x24: ffff000008099eac > > [ 25.832449] x23: 0000000000400000 x22: 0000000000000000 > > [ 25.837747] x21: 0000000000000001 x20: 0000000000000000 > > [ 25.843045] x19: 0000000000400000 x18: 0000000000010e00 > > [ 25.848343] x17: 000000000437f790 x16: 0000000000000020 > > [ 25.853641] x15: 0000000000000000 x14: 6549435020524541 > > [ 25.858939] x13: 20454d502067756c x12: 0000000000000000 > > [ 25.864237] x11: ffff00000996f6f0 x10: 0000000000000006 > > [ 25.869536] x9 : 00000000000012a4 x8 : ffff8023c000ff90 > > [ 25.874834] x7 : 0000000000000000 x6 : ffff000008d73c08 > > [ 25.880132] x5 : 0000000000000000 x4 : 0000000000000081 > > [ 25.885430] x3 : 0000000000000000 x2 : 0000000000000000 > > [ 25.890728] x1 : 0000000000000001 x0 : 0000000000001980 > > [ 25.896027] Process swapper/0 (pid: 1, stack limit = 0x (ptrval)) > > [ 25.902712] Call trace: > > [ 25.905146] __alloc_pages_nodemask+0xf0/0xe70 > > [ 25.909577] allocate_slab+0x94/0x590 > > [ 25.913225] new_slab+0x68/0xc8 > > [ 25.916353] ___slab_alloc+0x444/0x4f8 > > [ 25.920088] __slab_alloc+0x50/0x68 > > [ 25.923562] kmem_cache_alloc_node_trace+0xe8/0x230 > > [ 25.928426] pci_acpi_scan_root+0x94/0x278 > > [ 25.932510] acpi_pci_root_add+0x228/0x4b0 > > [ 25.936593] acpi_bus_attach+0x10c/0x218 > > [ 25.940501] acpi_bus_attach+0xac/0x218 > > [ 25.944323] acpi_bus_attach+0xac/0x218 > > [ 25.948144] acpi_bus_scan+0x5c/0xc0 > > [ 25.951708] acpi_scan_init+0xf8/0x254 > > [ 25.955443] acpi_init+0x310/0x37c > > [ 25.958831] do_one_initcall+0x54/0x208 > > [ 25.962653] kernel_init_freeable+0x244/0x340 > > [ 25.966999] kernel_init+0x18/0x118 > > [ 25.970474] ret_from_fork+0x10/0x1c > > [ 25.974036] Code: 7100047f 321902a4 1a950095 b5000602 (b9400803) > > [ 25.980162] ---[ end trace 64f0893eb21ec283 ]--- > > [ 25.984765] Kernel panic - not syncing: Fatal exception > > > > Signed-off-by: Xie XiuQi <xiexiuqi@xxxxxxxxxx> > > Tested-by: Huiqiang Wang <wanghuiqiang@xxxxxxxxxx> > > Cc: Hanjun Guo <hanjun.guo@xxxxxxxxxx> > > Cc: Tomasz Nowicki <Tomasz.Nowicki@xxxxxxxxxxxxxxxxxx> > > Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx> > > --- > > arch/arm64/kernel/pci.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c > > index 0e2ea1c..e17cc45 100644 > > --- a/arch/arm64/kernel/pci.c > > +++ b/arch/arm64/kernel/pci.c > > @@ -170,6 +170,9 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root) > > struct pci_bus *bus, *child; > > struct acpi_pci_root_ops *root_ops; > > > > + if (node != NUMA_NO_NODE && !node_online(node)) > > + node = NUMA_NO_NODE; > > + > > This really feels like a bodge, but it does appear to be what other > architectures do, so: > > Acked-by: Will Deacon <will.deacon@xxxxxxx> I agree, this doesn't feel like something we should be avoiding in the caller of kzalloc_node(). I would not expect kzalloc_node() to return memory that's offline, no matter what node we told it to allocate from. I could imagine it returning failure, or returning memory from a node that *is* online, but returning a pointer to offline memory seems broken. Are we putting memory that's offline in the free list? I don't know where to look to figure this out. Bjorn
