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| author | Peter Zijlstra <peterz@infradead.org> | 2020-11-26 14:04:46 +0100 |
|---|---|---|
| committer | Dave Hansen <dave.hansen@linux.intel.com> | 2022-12-15 10:37:27 -0800 |
| commit | 93b3037a1482758349f3b0431406bcc457ca1cbc (patch) | |
| tree | f0b65bbda3a866f5ae46725cc9737f7b56be020c /include | |
| parent | 60463628c9e0a8060ac6bef0457b0505c7532c7c (diff) | |
| download | linux-93b3037a1482758349f3b0431406bcc457ca1cbc.tar.bz2 | |
mm: Update ptep_get_lockless()'s comment
Improve the comment.
Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20221022114424.515572025%40infradead.org
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/pgtable.h | 15 |
1 files changed, 6 insertions, 9 deletions
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index a108b60a6962..c0b29000c3c0 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -300,15 +300,12 @@ static inline pte_t ptep_get(pte_t *ptep) #ifdef CONFIG_GUP_GET_PTE_LOW_HIGH /* - * WARNING: only to be used in the get_user_pages_fast() implementation. - * - * With get_user_pages_fast(), we walk down the pagetables without taking any - * locks. For this we would like to load the pointers atomically, but sometimes - * that is not possible (e.g. without expensive cmpxchg8b on x86_32 PAE). What - * we do have is the guarantee that a PTE will only either go from not present - * to present, or present to not present or both -- it will not switch to a - * completely different present page without a TLB flush in between; something - * that we are blocking by holding interrupts off. + * For walking the pagetables without holding any locks. Some architectures + * (eg x86-32 PAE) cannot load the entries atomically without using expensive + * instructions. We are guaranteed that a PTE will only either go from not + * present to present, or present to not present -- it will not switch to a + * completely different present page without a TLB flush inbetween; which we + * are blocking by holding interrupts off. * * Setting ptes from not present to present goes: * |