tree 0382a5fbe462f5a88056b3f4e7b460e82f4795bb
parent e5289d4a181fb6c0b7a7607649af2ffdc491335c
author Ingo Molnar <mingo@elte.hu> 1245058501 +0200
committer Ingo Molnar <mingo@elte.hu> 1245423316 +0200

perf_counter, x86: Improve interactions with fast-gup

Improve a few details in perfcounter call-chain recording that
makes use of fast-GUP:

- Use ACCESS_ONCE() to observe the pte value. ptes are fundamentally
  racy and can be changed on another CPU, so we have to be careful
  about how we access them. The PAE branch is already careful with
  read-barriers - but the non-PAE and 64-bit side needs an
  ACCESS_ONCE() to make sure the pte value is observed only once.

- make the checks a bit stricter so that we can feed it any kind of
  cra^H^H^H user-space input ;-)

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>