Subject: Re: kernel panics with crashkernel=256M while booting

From: Benjamin Herrenschmidt <[email-masked]>
Date: Wed, 07 Jan 2009 12:50:17 +1100

On Mon, 2008-12-22 at 16:14 +0530, Chandru wrote:
> On a ppc64 machine booting linux-2.6.28-rc9 with crashkernel=256M@32M boot 
> parameter caused the kernel to panic while booting.  Follwing is the console 
> message..

This is a fix to generic code. Can you resubmit it to linux-mm and/or
linux-kernel ? You can still CC linuxppc-dev but it should be handled by
one of the core mm maintainers.

Cheers,
Ben.

> =================================
> <snip>
> ...
> Calling quiesce ...
> returning from prom_init
> Reserving 256MB of memory at 32MB for crashkernel (System RAM: 4096MB)
> Phyp-dump disabled at boot time
> Using pSeries machine description
> Using 1TB segments
> Found initrd at 0xc000000000e00000:0xc0000000015ab50c
> console [udbg0] enabled
> Partition configured for 4 cpus.
> CPU maps initialized for 2 threads per core
> Starting Linux PPC64 #3 SMP Mon Dec 22 02:16:31 CST 2008
> -----------------------------------------------------
> ppc64_pft_size                = 0x1a
> physicalMemorySize            = 0x100000000
> htab_hash_mask                = 0x7ffff
> -----------------------------------------------------
> Initializing cgroup subsys cpuset
> Initializing cgroup subsys cpu
> Linux version 2.6.28-rc9-1-ppc64 (root@rulerlp10) (gcc version 4.3.2 
> [gcc-4_3-branch revision 141291] (SUSE Linux) ) #3 SMP Mon Dec 22 02:16:31 CST 
> 2008
> [boot]0012 Setup Arch
> ------------[ cut here ]------------
> kernel BUG at mm/bootmem.c:279!
> Oops: Exception in kernel mode, sig: 5 [#1]
> SMP NR_CPUS=1024 NUMA pSeries
> Modules linked in:
> NIP: c000000000747538 LR: c000000000731d1c CTR: c000000000730cf4
> REGS: c000000000993a00 TRAP: 0700   Not tainted  (2.6.28-rc9-1-ppc64)
> MSR: 8000000000021032 <ME,IR,DR>  CR: 24002082  XER: 00000001
> TASK = c0000000008dfaa0[0] 'swapper' THREAD: c000000000990000 CPU: 0
> GPR00: 0000000000000001 c000000000993c80 c00000000098a768 c0000000007664d0
> GPR04: 00000000000001f7 0000000000001001 0000000000000001 0000000000000000
> GPR08: 0000000000000000 0000000000000000 c0000000008dd6c0 0000000000000000
> GPR12: 0000000024002088 c000000000a52c00 c000000000763990 c00000000067f735
> GPR16: 00000000034638c8 0000000000000000 c000000000993d98 c000000000993d90
> GPR20: c000000000993da0 c000000000c32bc8 c000000001f78800 c000000000000000
> GPR24: 0000000000000004 0000000010087800 0000000000000000 0000000000000001
> GPR28: 00000000000001f7 0000000000001001 c000000000910cb0 c0000000007664d0
> NIP [c000000000747538] .mark_bootmem_node+0xa8/0x120
> LR [c000000000731d1c] .do_init_bootmem+0xc1c/0xd58
> Call Trace:
> [c000000000993c80] [c000000000993d20] init_thread_union+0x3d20/0x4000 
> (unreliable)
> [c000000000993d20] [c000000000731d1c] .do_init_bootmem+0xc1c/0xd58
> [c000000000993e40] [c0000000007267f0] .setup_arch+0x1a4/0x21c
> [c000000000993ee0] [c000000000720868] .start_kernel+0xdc/0x56c
> [c000000000993f90] [c0000000000083b8] .start_here_common+0x1c/0x64
> Instruction dump:
> 7ca501d2 4bda924d 60000000 e93f0000 7c09e010 7c000110 7c0000d0 0b000000
> e81f0008 7c1d0010 7c000110 7c0000d0 <0b000000> 2fbb0000 7ca9e850 7c89e050
> ---[ end trace 31fd0ba7d8756001 ]---
> Kernel panic - not syncing: Attempted to kill the idle task!
> ------------[ cut here ]------------
> Badness at kernel/smp.c:333
> NIP: c0000000000b9384 LR: c0000000000b96ac CTR: 0000000000136f8c
> REGS: c000000000992eb0 TRAP: 0700   Tainted: G      D     (2.6.28-rc9-1-ppc64)
> MSR: 8000000000021032 <ME,IR,DR>  CR: 28002084  XER: 00000001
> TASK = c0000000008dfaa0[0] 'swapper' THREAD: c000000000990000 CPU: 0
> GPR00: 0000000000000001 c000000000993130 c00000000098a768 0000000000000001
> GPR04: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> GPR12: 0000000028002082 c000000000a52c00 c000000000763990 c00000000067f735
> GPR16: 00000000034638c8 0000000000000000 c000000000993d98 c000000000993d90
> GPR20: c000000000993da0 c000000000c32bc8 c000000001f78800 0000000000000000
> GPR24: c000000000926320 0000000000000000 0000000000000000 0000000000000000
> GPR28: 0000000000000000 0000000000000000 c00000000090f4f8 c000000000af8380
> NIP [c0000000000b9384] .smp_call_function_mask+0x6c/0x2f4
> LR [c0000000000b96ac] .smp_call_function+0xa0/0xcc
> Call Trace:
> [c000000000993130] [c0000000009931d0] init_thread_union+0x31d0/0x4000 
> (unreliable)
> [c000000000993420] [c0000000000b96ac] .smp_call_function+0xa0/0xcc
> [c000000000993530] [c00000000002ce0c] .smp_send_stop+0x24/0x3c
> [c0000000009935b0] [c0000000004f0658] .panic+0x98/0x198
> [c000000000993640] [c00000000008fe18] .do_exit+0xa0/0x900
> [c000000000993730] [c000000000027984] .die+0x274/0x278
> [c0000000009937d0] [c000000000027c78] ._exception+0x88/0x20c
> [c000000000993990] [c000000000004f8c] program_check_common+0x10c/0x180
> --- Exception: 700 at .mark_bootmem_node+0xa8/0x120
>     LR = .do_init_bootmem+0xc1c/0xd58
> [c000000000993c80] [c000000000993d20] init_thread_union+0x3d20/0x4000 
> (unreliable)
> [c000000000993d20] [c000000000731d1c] .do_init_bootmem+0xc1c/0xd58
> [c000000000993e40] [c0000000007267f0] .setup_arch+0x1a4/0x21c
> [c000000000993ee0] [c000000000720868] .start_kernel+0xdc/0x56c
> [c000000000993f90] [c0000000000083b8] .start_here_common+0x1c/0x64
> Instruction dump:
> eae103a8 eb4103b6 f8810328 f8a10330 f8c10338 f8e10340 f9010348 f9210350
> f9410358 880d01da 7c000074 7800d182 <0b000000> 3b8100d8 a3ad000a e89e8028
> Rebooting in 180 seconds..                                         
> =================================
> 
> 
> 
> When booted with crashkernel=224M@32M or any memory size less than this, the 
> system boots properly. The following was the observation.. 
> The system comes up with two nodes (0-256M and 256M-4GB).  The crashkernel 
> memory reservation spans across these two nodes.  The 
> mark_reserved_regions_for_nid() in arch/powerpc/mm/numa.c resizes the reserved 
> part of the memory within it as...
> ...
> ...
>             if (end_pfn > node_ar.end_pfn)
>                 reserve_size = (node_ar.end_pfn << PAGE_SHIFT)
>                     - (start_pfn << PAGE_SHIFT);
> 
> 
> but the reserve_bootmem_node() in mm/bootmem.c raises the pfn value of end 
> 
>     end = PFN_UP(physaddr + size);
> 
> This causes end to get a value past the last page in the 0-256M node.  Again 
> when reserve_bootmem_node() returns,  mark_reserved_regions_for_nid() loops 
> around to set the rest of the crashkernel memory in the next node as reserved.  
> It references NODE_DATA(node_ar.nid) and this causes another 'Oops: kernel 
> access of bad area' problem. The following changes made the system to boot 
> with any amount of crashkernel memory size.
> 
> 
> Fix code for reserved memory spanning acroos nodes
> 
> Signed-off-by: Chandru S <[email-masked]>
> ---
> 
> --- linux-2.6.28-rc9//arch/powerpc/mm/numa.c.orig	2008-12-22 
> 04:23:24.000000000 -0600
> +++ linux-2.6.28-rc9/arch/powerpc/mm/numa.c	2008-12-22 04:24:25.000000000 -0600
> @@ -995,10 +995,11 @@ void __init do_init_bootmem(void)
>  				  start_pfn, end_pfn);
>  
>  		free_bootmem_with_active_regions(nid, end_pfn);
> +	}
> +
> +	for_each_online_node(nid) {
>  		/*
> -		 * Be very careful about moving this around.  Future
> -		 * calls to careful_allocation() depend on this getting
> -		 * done correctly.
> +		 * Be very careful about moving this around.
>  		 */
>  		mark_reserved_regions_for_nid(nid);
>  		sparse_memory_present_with_active_regions(nid);
> --- linux-2.6.28-rc9/mm/bootmem.c.orig	2008-12-19 10:49:24.000000000 -0600
> +++ linux-2.6.28-rc9/mm/bootmem.c	2008-12-19 10:49:33.000000000 -0600
> @@ -375,10 +375,14 @@ int __init reserve_bootmem_node(pg_data_
>  				 unsigned long size, int flags)
>  {
>  	unsigned long start, end;
> +	bootmem_data_t *bdata = pgdat->bdata;
>  
>  	start = PFN_DOWN(physaddr);
>  	end = PFN_UP(physaddr + size);
>  
> +	if (end > bdata->node_low_pfn)
> +		end = bdata->node_low_pfn;
> +
>  	return mark_bootmem_node(pgdat->bdata, start, end, 1, flags);
>  }
> 
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