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| author | Uros Bizjak <ubizjak@gmail.com> | 2023-01-16 19:34:46 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-01-26 13:49:39 +0300 |
| commit | 50fd4d5e6914b60ea6f89c2cbff7a07799414c62 (patch) | |
| tree | 1b0fb8d3451fa4917a7b64207f0b1527eb4a8572 /arch/x86/mm | |
| parent | 1d61659ced6bd8881cf2fb5cbcb28f9541fc7430 (diff) | |
| download | linux-50fd4d5e6914b60ea6f89c2cbff7a07799414c62.tar.xz | |
x86/PAT: Use try_cmpxchg() in set_page_memtype()
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
set_page_memtype. x86 CMPXCHG instruction returns success in ZF flag,
so this change saves a compare after cmpxchg (and related move
instruction in front of cmpxchg).
Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg
fails. There is no need to re-read the value in the loop.
Note that the value from *ptr should be read using READ_ONCE to prevent
the compiler from merging, refetching or reordering the read.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230116163446.4734-1-ubizjak@gmail.com
Diffstat (limited to 'arch/x86/mm')
| -rw-r--r-- | arch/x86/mm/pat/memtype.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c index fb4b1b5e0dea..6d1ba2dda35d 100644 --- a/arch/x86/mm/pat/memtype.c +++ b/arch/x86/mm/pat/memtype.c @@ -159,10 +159,10 @@ static inline void set_page_memtype(struct page *pg, break; } + old_flags = READ_ONCE(pg->flags); do { - old_flags = pg->flags; new_flags = (old_flags & _PGMT_CLEAR_MASK) | memtype_flags; - } while (cmpxchg(&pg->flags, old_flags, new_flags) != old_flags); + } while (!try_cmpxchg(&pg->flags, &old_flags, new_flags)); } #else static inline enum page_cache_mode get_page_memtype(struct page *pg) |