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Dave Hansen 4a6186696e powerpc: Fix boot freeze on machine with empty memory node 
I got a bug report about a distro kernel not booting on a particular
machine.  It would freeze during boot:

> ...
> Could not find start_pfn for node 1
> [boot]0015 Setup Done
> Built 2 zonelists in Node order, mobility grouping on.  Total pages: 123783
> Policy zone: DMA
> Kernel command line:
> [boot]0020 XICS Init
> [boot]0021 XICS Done
> PID hash table entries: 4096 (order: 12, 32768 bytes)
> clocksource: timebase mult[7d0000] shift[22] registered
> Console: colour dummy device 80x25
> console handover: boot [udbg0] -> real [hvc0]
> Dentry cache hash table entries: 1048576 (order: 7, 8388608 bytes)
> Inode-cache hash table entries: 524288 (order: 6, 4194304 bytes)
> freeing bootmem node 0

I've reproduced this on 2.6.27.7.  It is caused by commit
8f64e1f2d1 ("powerpc: Reserve in bootmem
lmb reserved regions that cross NUMA nodes").

The problem is that Jon took a loop which was (in pseudocode):

	for_each_node(nid)
		NODE_DATA(nid) = careful_alloc(nid);
		setup_bootmem(nid);
		reserve_node_bootmem(nid);

and broke it up into:

	for_each_node(nid)
		NODE_DATA(nid) = careful_alloc(nid);
		setup_bootmem(nid);
	for_each_node(nid)
		reserve_node_bootmem(nid);

The issue comes in when the 'careful_alloc()' is called on a node with
no memory.  It falls back to using bootmem from a previously-initialized
node.  But, bootmem has not yet been reserved when Jon's patch is
applied.  It gives back bogus memory (0xc000000000000000) and pukes
later in boot.

The following patch collapses the loop back together.  It also breaks
the mark_reserved_regions_for_nid() code out into a function and adds
some comments.  I think a huge part of introducing this bug is because
for loop was too long and hard to read.

The actual bug fix here is the:

+		if (end_pfn <= node->node_start_pfn ||
+		    start_pfn >= node_end_pfn)
+			continue;

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2008-12-01 09:40:18 +11:00
..
boot powerpc/mpc832x_rdb: fix swapped ethernet ids 2008-11-19 15:12:19 -06:00
configs Merge branch 'merge' of git://git.secretlab.ca/git/linux-2.6-mpc52xx into merge 2008-11-24 11:53:44 +11:00
include/asm powerpc: Update QE/CPM2 usb_ctlr structures for USB support 2008-11-08 12:39:02 -06:00
kernel powerpc: Fix IRQ assignment for some PCIe devices 2008-12-01 09:40:18 +11:00
kvm KVM: switch to get_user_pages_fast 2008-10-15 14:25:06 +02:00
lib powerpc: Fix DMA offset for non-coherent DMA 2008-10-14 10:35:26 +11:00
math-emu powerpc/math-emu: Use kernel generic math-emu code 2008-10-01 08:40:07 -05:00
mm powerpc: Fix boot freeze on machine with empty memory node 2008-12-01 09:40:18 +11:00
oprofile powerpc/cell/OProfile: Fix on-stack array size in activate spu profiling function 2008-10-31 16:13:51 +11:00
platforms Merge branch 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/jk/spufs into merge 2008-11-24 11:54:08 +11:00
sysdev powerpc/virtex: fix various format/casting printk mismatches 2008-11-14 09:59:48 -07:00
xmon powerpc: Fix compile errors with CONFIG_BUG=n 2008-10-31 21:34:09 +11:00
Kconfig Merge commit 'v2.6.28-rc2' into tracing/urgent 2008-10-27 10:50:54 +01:00
Kconfig.debug powerpc: Split-out common MSI bitmap logic into msi_bitmap.c 2008-08-20 16:34:57 +10:00
Makefile ftrace: rename FTRACE to FUNCTION_TRACER 2008-10-20 18:27:03 +02:00