Messages in this thread | | | Subject | Re: [PATCH 1/3] powerpc: Allocate per-cpu areas for node IDs for SLQB to use as per-node areas | From | Daniel Walker <> | Date | Mon, 21 Sep 2009 10:17:52 -0700 |
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On Mon, 2009-09-21 at 17:10 +0100, Mel Gorman wrote: > SLQB uses DEFINE_PER_CPU to define per-node areas. An implicit > assumption is made that all valid node IDs will have matching valid CPU > ids. In memoryless configurations, it is possible to have a node ID with > no CPU having the same ID. When this happens, a per-cpu are is not > created and the value of paca[cpu].data_offset is some random value. > This is later deferenced and the system crashes after accessing some > invalid address. > > This patch hacks powerpc to allocate per-cpu areas for node IDs that > have no corresponding CPU id. This gets around the immediate problem but > it should be discussed if there is a requirement for a DEFINE_PER_NODE > and how it should be implemented. > > Signed-off-by: Mel Gorman <mel@csn.ul.ie> > --- > arch/powerpc/kernel/setup_64.c | 20 ++++++++++++++++++++ > 1 files changed, 20 insertions(+), 0 deletions(-) > > diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c > index 1f68160..a5f52d4 100644 > --- a/arch/powerpc/kernel/setup_64.c > +++ b/arch/powerpc/kernel/setup_64.c > @@ -588,6 +588,26 @@ void __init setup_per_cpu_areas(void) > paca[i].data_offset = ptr - __per_cpu_start; > memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start); > } > +#ifdef CONFIG_SLQB > + /* > + * SLQB abuses DEFINE_PER_CPU to setup a per-node area. This trick > + * assumes that ever node ID will have a CPU of that ID to match. > + * On systems with memoryless nodes, this may not hold true. Hence, > + * we take a second pass initialising a "per-cpu" area for node-ids > + * that SLQB can use > + */
Very trivial, but there's a little trailing whitespace in the first line of the comment (checkpatch warns on it.) You also spelled initializing wrong.
Daniel
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