From 5872f1a2e5c783783d51e96468f0ff6aede61182 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Mon, 11 May 2020 21:59:51 +0100 Subject: 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 Cc: Peter Zijlstra Reported-by: Jann Horn Signed-off-by: Will Deacon --- include/linux/compiler.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'include/linux/compiler.h') 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), \ -- cgit