diff mbox series

[v1,5/5] riscv/cmpxchg: Implement xchg for variables of size 1 and 2

Message ID 20240103163203.72768-7-leobras@redhat.com (mailing list archive)
State Accepted
Commit a8ed2b7a2c13cb8a613cc9a8862688a1385b942d
Headers show
Series Rework & improve riscv cmpxchg.h and atomic.h | expand

Checks

Context Check Description
conchuod/vmtest-for-next-PR success PR summary
conchuod/patch-5-test-1 success .github/scripts/patches/tests/build_rv32_defconfig.sh
conchuod/patch-5-test-2 success .github/scripts/patches/tests/build_rv64_clang_allmodconfig.sh
conchuod/patch-5-test-3 success .github/scripts/patches/tests/build_rv64_gcc_allmodconfig.sh
conchuod/patch-5-test-4 success .github/scripts/patches/tests/build_rv64_nommu_k210_defconfig.sh
conchuod/patch-5-test-5 success .github/scripts/patches/tests/build_rv64_nommu_virt_defconfig.sh
conchuod/patch-5-test-6 success .github/scripts/patches/tests/checkpatch.sh
conchuod/patch-5-test-7 success .github/scripts/patches/tests/dtb_warn_rv64.sh
conchuod/patch-5-test-8 success .github/scripts/patches/tests/header_inline.sh
conchuod/patch-5-test-9 success .github/scripts/patches/tests/kdoc.sh
conchuod/patch-5-test-10 success .github/scripts/patches/tests/module_param.sh
conchuod/patch-5-test-11 success .github/scripts/patches/tests/verify_fixes.sh
conchuod/patch-5-test-12 success .github/scripts/patches/tests/verify_signedoff.sh

Commit Message

Leonardo Bras Jan. 3, 2024, 4:32 p.m. UTC 
xchg for variables of size 1-byte and 2-bytes is not yet available for
riscv, even though its present in other architectures such as arm64 and
x86. This could lead to not being able to implement some locking mechanisms
or requiring some rework to make it work properly.

Implement 1-byte and 2-bytes xchg in order to achieve parity with other
architectures.

Signed-off-by: Leonardo Bras <leobras@redhat.com>
Tested-by: Guo Ren <guoren@kernel.org>
---
 arch/riscv/include/asm/cmpxchg.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
diff mbox series

Patch

diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
index ac9d0eeb74e67..26cea2395aae8 100644
--- a/arch/riscv/include/asm/cmpxchg.h
+++ b/arch/riscv/include/asm/cmpxchg.h
@@ -11,6 +11,31 @@ 
 #include <asm/barrier.h>
 #include <asm/fence.h>
 
+#define __arch_xchg_masked(prepend, append, r, p, n)			\
+({									\
+	u32 *__ptr32b = (u32 *)((ulong)(p) & ~0x3);			\
+	ulong __s = ((ulong)(p) & (0x4 - sizeof(*p))) * BITS_PER_BYTE;	\
+	ulong __mask = GENMASK(((sizeof(*p)) * BITS_PER_BYTE) - 1, 0)	\
+			<< __s;						\
+	ulong __newx = (ulong)(n) << __s;				\
+	ulong __retx;							\
+	ulong __rc;							\
+									\
+	__asm__ __volatile__ (						\
+	       prepend							\
+	       "0:	lr.w %0, %2\n"					\
+	       "	and  %1, %0, %z4\n"				\
+	       "	or   %1, %1, %z3\n"				\
+	       "	sc.w %1, %1, %2\n"				\
+	       "	bnez %1, 0b\n"					\
+	       append							\
+	       : "=&r" (__retx), "=&r" (__rc), "+A" (*(__ptr32b))	\
+	       : "rJ" (__newx), "rJ" (~__mask)				\
+	       : "memory");						\
+									\
+	r = (__typeof__(*(p)))((__retx & __mask) >> __s);		\
+})
+
 #define __arch_xchg(sfx, prepend, append, r, p, n)			\
 ({									\
 	__asm__ __volatile__ (						\
@@ -27,7 +52,13 @@ 
 	__typeof__(ptr) __ptr = (ptr);					\
 	__typeof__(*(__ptr)) __new = (new);				\
 	__typeof__(*(__ptr)) __ret;					\
+									\
 	switch (sizeof(*__ptr)) {					\
+	case 1:								\
+	case 2:								\
+		__arch_xchg_masked(prepend, append,			\
+				   __ret, __ptr, __new);		\
+		break;							\
 	case 4:								\
 		__arch_xchg(".w" sfx, prepend, append,			\
 			      __ret, __ptr, __new);			\