Felix-Gong commented on code in PR #3355:
URL: https://github.com/apache/brpc/pull/3355#discussion_r3472545643
##########
src/bthread/task_group.cpp:
##########
@@ -85,37 +85,100 @@ BAIDU_VOLATILE_THREAD_LOCAL(void*, tls_unique_user_ptr,
NULL);
const TaskStatistics EMPTY_STAT = { 0, 0, 0 };
AtomicInteger128::Value AtomicInteger128::load() const {
-#if __x86_64__ || __ARM_NEON
- // Supress compiler warning.
- (void)_mutex;
-#endif // __x86_64__ || __ARM_NEON
-
-#if __x86_64__ || __ARM_NEON
#ifdef __x86_64__
+ (void)_mutex;
+ (void)_seq;
__m128i value = _mm_load_si128(reinterpret_cast<const __m128i*>(&_value));
-#else // __ARM_NEON
+ return {value[0], value[1]};
+#elif defined(__ARM_NEON)
+ (void)_mutex;
+ (void)_seq;
int64x2_t value = vld1q_s64(reinterpret_cast<const int64_t*>(&_value));
-#endif // __x86_64__
return {value[0], value[1]};
-#else // __x86_64__ || __ARM_NEON
- // RISC-V and other architectures use mutex fallback
+#elif defined(__riscv)
+ (void)_mutex;
+ // RISC-V: Seqlock-based atomic 128-bit load.
+ int64_t v1, v2;
+ uint64_t seq0, seq1;
+ do {
+ __asm__ volatile(
+ "ld %0, %1\n\t"
+ : "=r"(seq0)
+ : "m"(_seq)
+ : "memory"
+ );
+ if (seq0 & 1) continue;
+ __asm__ volatile("fence r, rw\n\t" ::: "memory");
+ __asm__ volatile(
+ "ld %0, %2\n\t"
+ "ld %1, %3\n\t"
+ : "=r"(v1), "=r"(v2)
+ : "m"(_value.v1), "m"(_value.v2)
+ : "memory"
+ );
+ __asm__ volatile("fence r, rw\n\t" ::: "memory");
+ __asm__ volatile(
+ "ld %0, %1\n\t"
+ : "=r"(seq1)
+ : "m"(_seq)
+ : "memory"
+ );
+ } while (seq0 != seq1);
+ return {v1, v2};
+#else
BAIDU_SCOPED_LOCK(const_cast<FastPthreadMutex&>(_mutex));
return _value;
-#endif // __x86_64__ || __ARM_NEON
+#endif
}
void AtomicInteger128::store(Value value) {
-#if __x86_64__
+#ifdef __x86_64__
+ (void)_seq;
__m128i v = _mm_load_si128(reinterpret_cast<__m128i*>(&value));
_mm_store_si128(reinterpret_cast<__m128i*>(&_value), v);
-#elif __ARM_NEON
+#elif defined(__ARM_NEON)
+ (void)_seq;
int64x2_t v = vld1q_s64(reinterpret_cast<int64_t*>(&value));
vst1q_s64(reinterpret_cast<int64_t*>(&_value), v);
+#elif defined(__riscv)
Review Comment:
Fixed. Added `&& __riscv_xlen == 64` guard for store() as well. RV32 builds
will use the mutex fallback.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
