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authorIngo Molnar <mingo@elte.hu>2009-06-15 05:35:01 -0400
committerIngo Molnar <mingo@elte.hu>2009-06-19 10:55:16 -0400
commit0c87197142427063e096f11603543ca874045952 (patch)
tree0382a5fbe462f5a88056b3f4e7b460e82f4795bb /arch/x86/mm/gup.c
parente5289d4a181fb6c0b7a7607649af2ffdc491335c (diff)
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>
Diffstat (limited to 'arch/x86/mm/gup.c')
-rw-r--r--arch/x86/mm/gup.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index 697d5727c119..2d1d784ad3f7 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -14,7 +14,7 @@
14static inline pte_t gup_get_pte(pte_t *ptep) 14static inline pte_t gup_get_pte(pte_t *ptep)
15{ 15{
16#ifndef CONFIG_X86_PAE 16#ifndef CONFIG_X86_PAE
17 return *ptep; 17 return ACCESS_ONCE(*ptep);
18#else 18#else
19 /* 19 /*
20 * With get_user_pages_fast, we walk down the pagetables without taking 20 * With get_user_pages_fast, we walk down the pagetables without taking