Re: 5.0-rc kernel hangs on early boot

[Yury Norov <yury.norov@gmail.com>]

On Wed, Feb 13, 2019 at 11:18:44AM +0000, Will Deacon wrote:
> Hi Yury,
> 
> On Wed, Feb 13, 2019 at 11:25:40AM +0300, Yury Norov wrote:
> > My kernel on qemu/arm64 setup hangs at early boot since v5.0-rc1.
> > Backtrace is not too verbose:
> > (gdb) i threads
> >   Id   Target Id         Frame
> > * 1    Thread 1 (CPU#0 [running]) 0xffff000010a49b74 in __delay (cycles=4096)
> >     at arch/arm64/lib/delay.c:49
> >   2    Thread 2 (CPU#1 [halted ]) 0x0000000000000000 in ?? ()
> >   3    Thread 3 (CPU#2 [halted ]) 0x0000000000000000 in ?? ()
> >   4    Thread 4 (CPU#3 [halted ]) 0x0000000000000000 in ?? ()
> > (gdb) bt
> > #0  0xffff000010a49b74 in __delay (cycles=4096) at arch/arm64/lib/delay.c:49
> > Backtrace stopped: previous frame identical to this frame (corrupt stack?)
> > 
> > Reverting the patch
> > 1c30844d2dfe272d58c ("mm: reclaim small amounts of memory when an external
> > fragmentation event occurs") together with following patch
> > 73444bc4d8f92e46a20 ("mm, page_alloc: do not wake kswapd with zone lock held")
> > helps me to boot normally. 
> > 
> > Some system information is below, and config is attached.
> 
> FWIW, running with your command-line and .config under KVM with earlycon
> leads to an early page allocation failure followed by a NULL dereference
> during boot if only 1G is configured (log below). For the mm folks, it's
> probably worth pointing out that you're using 64k pages.
> 
> Can you confirm that the kernel boots successfully if you pass more memory to
> qemu (e.g. 2gb)?

2G workaround works, I confirm. Also, Mel's fix provided in this thread works
as well.

Thanks,
Yury

> Will
> 
> --->8
> 
> [    0.000000] swapper: page allocation failure: order:0, mode:0x0(), nodemask=(null),cpuset=(null),mems_allowed=0-3
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc64.9.0+ #1
> [    0.000000] Hardware name: linux,dummy-virt (DT)
> [    0.000000] Call trace:
> [    0.000000]  dump_backtrace+0x0/0x178
> [    0.000000]  show_stack+0x24/0x30
> [    0.000000]  dump_stack+0x90/0xb4
> [    0.000000]  warn_alloc+0x100/0x188
> [    0.000000]  __alloc_pages_nodemask+0xd48/0xd88
> [    0.000000]  alloc_pages_current+0x8c/0xf8
> [    0.000000]  allocate_slab+0x370/0x4a8
> [    0.000000]  new_slab+0x98/0xc0
> [    0.000000]  ___slab_alloc+0x27c/0x510
> [    0.000000]  __slab_alloc+0x50/0x68
> [    0.000000]  kmem_cache_alloc+0x1d0/0x1f8
> [    0.000000]  bootstrap+0x34/0x170
> [    0.000000]  kmem_cache_init+0x9c/0x130
> [    0.000000]  start_kernel+0x240/0x464
> [    0.000000] Mem-Info:
> [    0.000000] active_anon:0 inactive_anon:0 isolated_anon:0
> [    0.000000]  active_file:0 inactive_file:0 isolated_file:0
> [    0.000000]  unevictable:0 dirty:0 writeback:0 unstable:0
> [    0.000000]  slab_reclaimable:0 slab_unreclaimable:1
> [    0.000000]  mapped:0 shmem:0 pagetables:0 bounce:0
> [    0.000000]  free:7737 free_pcp:0 free_cma:0
> [    0.000000] Node 0 active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB shmem:0kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
> [    0.000000] Node 0 DMA32 free:495168kB min:524288kB low:524288kB high:524288kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:1048576kB managed:495232kB mlocked:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
> [    0.000000] lowmem_reserve[]: 0 0 0
> [    0.000000] Node 0 DMA32: 1*64kB (U) 4*128kB (U) 2*256kB (U) 3*512kB (U) 3*1024kB (U) 1*2048kB (U) 3*4096kB (U) 2*8192kB (U) 2*16384kB (U) 3*32768kB (U) 3*65536kB (U) 1*131072kB (U) 0*262144kB 0*524288kB = 495168kB
> [    0.000000] 0 total pagecache pages
> [    0.000000] 0 pages in swap cache
> [    0.000000] Swap cache stats: add 0, delete 0, find 0/0
> [    0.000000] Free swap  = 0kB
> [    0.000000] Total swap = 0kB
> [    0.000000] 16384 pages RAM
> [    0.000000] 0 pages HighMem/MovableOnly
> [    0.000000] 8646 pages reserved
> [    0.000000] 8192 pages cma reserved
> [    0.000000] SLUB: Unable to allocate memory on node -1, gfp=0x408000(GFP_NOWAIT|__GFP_ZERO)
> [    0.000000]   cache: kmem_cache, object size: 336, buffer size: 384, default order: 0, min order: 0
> [    0.000000]   node 0: slabs: 0, objs: 0, free: 0
> [    0.000000] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> [    0.000000] Mem abort info:
> [    0.000000]   ESR = 0x96000045
> [    0.000000]   Exception class = DABT (current EL), IL = 32 bits
> [    0.000000]   SET = 0, FnV = 0
> [    0.000000]   EA = 0, S1PTW = 0
> [    0.000000] Data abort info:
> [    0.000000]   ISV = 0, ISS = 0x00000045
> [    0.000000]   CM = 0, WnR = 1
> [    0.000000] [0000000000000000] user address but active_mm is swapper
> [    0.000000] Internal error: Oops: 96000045 [#1] SMP
> [    0.000000] Modules linked in:
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc64.9.0+ #1
> [    0.000000] Hardware name: linux,dummy-virt (DT)
> [    0.000000] pstate: 20000085 (nzCv daIf -PAN -UAO)
> [    0.000000] pc : __memcpy+0x110/0x180
> [    0.000000] lr : bootstrap+0x48/0x170
> [    0.000000] sp : ffff00001104ff20
> [    0.000000] x29: ffff00001104ff20 x28: 0000000080ea0018 
> [    0.000000] x27: 0000000000000000 x26: 0000000000000000 
> [    0.000000] x25: 0000000000000000 x24: ffff000010f80008 
> [    0.000000] x23: ffff000010f92490 x22: ffff000011070000 
> [    0.000000] x21: ffff000010f92490 x20: ffff000011a1f000 
> [    0.000000] x19: 0000000000000000 x18: 0000000000000010 
> [    0.000000] x17: 0000000000000000 x16: 0000000000000000 
> [    0.000000] x15: ffffffffffffffff x14: 00000000ffffffff 
> [    0.000000] x13: 00000000000000aa x12: 000000aa000000aa 
> [    0.000000] x11: 0000000d00000000 x10: 0000015000000180 
> [    0.000000] x9 : 0000000000000005 x8 : 0000000040002000 
> [    0.000000] x7 : ffff000011030e80 x6 : 0000000000000000 
> [    0.000000] x5 : 0000000000000000 x4 : 0000000000000000 
> [    0.000000] x3 : 0000000000000000 x2 : 00000000000000d0 
> [    0.000000] x1 : ffff000010f924d0 x0 : 0000000000000000 
> [    0.000000] Process swapper (pid: 0, stack limit = 0x(____ptrval____))
> [    0.000000] Call trace:
> [    0.000000]  __memcpy+0x110/0x180
> [    0.000000]  kmem_cache_init+0x9c/0x130
> [    0.000000]  start_kernel+0x240/0x464
> [    0.000000] Code: a8c12027 a8c12829 a8c1302b a8c1382d (a88120c7) 
> [    0.000000] ---[ end trace a6053f496cb6dec0 ]---
> [    0.000000] Kernel panic - not syncing: Fatal exception
> [    0.000000] ---[ end Kernel panic - not syncing: Fatal exception ]---

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