coffee/cpp-ipc
1
0
Fork 0
mirror of https://github.com/mutouyun/cpp-ipc.git synced 2025-12-06 16:56:45 +08:00
Code Issues Packages Projects Releases Wiki Activity

optimize lock_shared

Browse Source
This commit is contained in:
mutouyun 2018-12-14 11:21:46 +08:00
parent 238f769f7a
commit 7b812c3c6e
1 changed files with 9 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
include/rw_lock.h
View File

@ -36,15 +36,18 @@ public:
} }
void lock_shared() { void lock_shared() {
for (unsigned k = 0;; ++k) {
auto old = lc_.load(std::memory_order_relaxed); auto old = lc_.load(std::memory_order_relaxed);
// if w_flag set, just continue; otherwise cas lc + 1 (set r-lock) for (unsigned k = 0;; ++k) {
if (!(old & w_flag) && // if w_flag set, just continue
lc_.compare_exchange_weak(old, old + 1, std::memory_order_acquire)) { if (old & w_flag) {
yield(k);
old = lc_.load(std::memory_order_acquire);
}
// otherwise try cas lc + 1 (set r-lock)
else if (lc_.compare_exchange_weak(old, old + 1, std::memory_order_acquire)) {
break; break;
} }
yield(k); // set r-lock failed, old has been updated
std::atomic_thread_fence(std::memory_order_acquire);
} }
} }