[PATCH v3 1/5] arch,locking/atomic: arc: arch_cmpxchg should check data size
From: wuqiang.matt
Date: Tue Nov 21 2023 - 09:25:31 EST
arch_cmpxchg() should check data size rather than pointer size in case
CONFIG_ARC_HAS_LLSC is defined. So rename __cmpxchg to __cmpxchg_32 to
emphasize it's explicit support of 32bit data size with BUILD_BUG_ON()
added to avoid any possible misuses with unsupported data types.
In case CONFIG_ARC_HAS_LLSC is undefined, arch_cmpxchg() uses spinlock
to accomplish SMP-safety, so the BUILD_BUG_ON checking is uncecessary.
v2 -> v3:
- Patches regrouped and has the improvement for xtensa included
- Comments refined to address why these changes are needed
v1 -> v2:
- Try using native cmpxchg variants if avaialble, as Arnd advised
Signed-off-by: wuqiang.matt <wuqiang.matt@xxxxxxxxxxxxx>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
---
arch/arc/include/asm/cmpxchg.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index e138fde067de..bf46514f6f12 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -18,14 +18,16 @@
* if (*ptr == @old)
* *ptr = @new
*/
-#define __cmpxchg(ptr, old, new) \
+#define __cmpxchg_32(ptr, old, new) \
({ \
__typeof__(*(ptr)) _prev; \
\
+ BUILD_BUG_ON(sizeof(*(ptr)) != 4); \
+ \
__asm__ __volatile__( \
- "1: llock %0, [%1] \n" \
+ "1: llock %0, [%1] \n" \
" brne %0, %2, 2f \n" \
- " scond %3, [%1] \n" \
+ " scond %3, [%1] \n" \
" bnz 1b \n" \
"2: \n" \
: "=&r"(_prev) /* Early clobber prevent reg reuse */ \
@@ -47,7 +49,7 @@
\
switch(sizeof((_p_))) { \
case 4: \
- _prev_ = __cmpxchg(_p_, _o_, _n_); \
+ _prev_ = __cmpxchg_32(_p_, _o_, _n_); \
break; \
default: \
BUILD_BUG(); \
@@ -65,8 +67,6 @@
__typeof__(*(ptr)) _prev_; \
unsigned long __flags; \
\
- BUILD_BUG_ON(sizeof(_p_) != 4); \
- \
/* \
* spin lock/unlock provide the needed smp_mb() before/after \
*/ \
--
2.40.1