[PATCH 1/3 v3] powerpc/32: Always order writes to halves of 64-bit PTEs

Kumar Gala galak at kernel.crashing.org
Tue Aug 18 10:00:22 EST 2009

On Aug 17, 2009, at 6:00 PM, Paul Mackerras wrote:

> On 32-bit systems with 64-bit PTEs, the PTEs have to be written in two
> 32-bit halves.  On SMP we write the higher-order half and then the
> lower-order half, with a write barrier between the two halves, but on
> UP there was no particular ordering of the writes to the two halves.
> This extends the ordering that we already do on SMP to the UP case as
> well.  The reason is that with the perf_counter subsystem potentially
> accessing user memory at interrupt time to get stack traces, we have
> to be careful not to create an incorrect but apparently valid PTE even
> on UP.
> Signed-off-by: Paul Mackerras <paulus at samba.org>
> ---
> arch/powerpc/include/asm/pgtable.h |    6 +++---
> 1 files changed, 3 insertions(+), 3 deletions(-)

Just out of interest did you end up hitting this in testing?

- k

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