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| author | Will Deacon <will@kernel.org> | 2020-05-11 21:59:51 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-06-05 11:02:44 +0100 |
| commit | 5872f1a2e5c783783d51e96468f0ff6aede61182 (patch) | |
| tree | 5b77d8a9917e6655f5f421221cfe6c4b38fc078b /include/linux/compiler.h | |
| parent | 10415533a9062c9e5e27c421d9c232f0cae108fd (diff) | |
| download | lwn-5872f1a2e5c783783d51e96468f0ff6aede61182.tar.gz lwn-5872f1a2e5c783783d51e96468f0ff6aede61182.zip | |
READ_ONCE: Fix comment describing 2x32-bit atomicity
READ_ONCE() permits 64-bit accesses on 32-bit architectures, since this
crops up in a few places and is generally harmless because either the
upper bits are always zero (e.g. for a virtual address or 32-bit time_t)
or the architecture provides 64-bit atomicity anyway.
Update the corresponding comment above compiletime_assert_rwonce_type(),
which incorrectly states that 32-bit x86 provides 64-bit atomicity, and
instead reference 32-bit Armv7 with LPAE.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index c363d8debc43..657e4fd38a77 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -332,9 +332,9 @@ static inline void *offset_to_ptr(const int *off) /* * Yes, this permits 64-bit accesses on 32-bit architectures. These will - * actually be atomic in many cases (namely x86), but for others we rely on - * the access being split into 2x32-bit accesses for a 32-bit quantity (e.g. - * a virtual address) and a strong prevailing wind. + * actually be atomic in some cases (namely Armv7 + LPAE), but for others we + * rely on the access being split into 2x32-bit accesses for a 32-bit quantity + * (e.g. a virtual address) and a strong prevailing wind. */ #define compiletime_assert_rwonce_type(t) \ compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ |