intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 113 insertions, 0 deletions

diff --git a/library/cpp/threading/light_rw_lock/lightrwlock.cpp b/library/cpp/threading/light_rw_lock/lightrwlock.cpp
new file mode 100644
index 0000000000..fbb63fd47f
--- /dev/null
+++ b/library/cpp/threading/light_rw_lock/lightrwlock.cpp
@@ -0,0 +1,113 @@
+#include "lightrwlock.h"
+#include <util/system/spinlock.h>
+
+#if defined(_linux_)
+
+using namespace NS_LightRWLock;
+
+void TLightRWLock::WaitForUntrappedShared() {
+    for (;;) {
+        for (ui32 i = 0; i < SpinCount_; ++i) {
+            SpinLockPause();
+
+            if ((AtomicLoad(Counter_) & 0x7FFFFFFF) == 0)
+                return;
+        }
+
+        SequenceStore(UnshareFutex_, 1);
+        if ((AtomicLoad(Counter_) & 0x7FFFFFFF) == 0) {
+            AtomicStore(UnshareFutex_, 0);
+            return;
+        }
+        FutexWait(UnshareFutex_, 1);
+    }
+}
+
+void TLightRWLock::WaitForExclusiveAndUntrappedShared() {
+    for (;;) {
+        for (ui32 i = 0; i < SpinCount_; ++i) {
+            SpinLockPause();
+
+            if (AtomicLoad(Counter_) >= 0)
+                goto try_to_get_lock;
+            if (AtomicLoad(TrappedFutex_) == 1)
+                goto skip_store_trapped;
+        }
+
+        SequenceStore(TrappedFutex_, 1);
+    skip_store_trapped:
+
+        if (AtomicLoad(Counter_) < 0) {
+            FutexWait(TrappedFutex_, 1);
+        }
+
+    try_to_get_lock:
+        if (!AtomicSetBit(Counter_, 31))
+            break;
+    }
+
+    for (ui32 j = 0;; ++j) {
+        for (ui32 i = 0; i < SpinCount_; ++i) {
+            if ((AtomicLoad(Counter_) & 0x7FFFFFFF) == 0)
+                return;
+
+            SpinLockPause();
+        }
+
+        SequenceStore(UnshareFutex_, 1);
+
+        if ((AtomicLoad(Counter_) & 0x7FFFFFFF) == 0) {
+            AtomicStore(UnshareFutex_, 0);
+            return;
+        }
+
+        FutexWait(UnshareFutex_, 1);
+    }
+}
+
+void TLightRWLock::WaitForUntrappedAndAcquireRead() {
+    if (AtomicFetchAdd(Counter_, -1) < 0)
+        goto skip_lock_try;
+
+    for (;;) {
+    again:
+        if (Y_UNLIKELY(AtomicFetchAdd(Counter_, 1) >= 0)) {
+            return;
+        } else {
+            if (AtomicFetchAdd(Counter_, -1) >= 0)
+                goto again;
+        }
+
+    skip_lock_try:
+        if (AtomicLoad(UnshareFutex_) && (AtomicLoad(Counter_) & 0x7FFFFFFF) == 0) {
+            SequenceStore(UnshareFutex_, 0);
+            FutexWake(UnshareFutex_, 1);
+        }
+
+        for (;;) {
+            for (ui32 i = 0; i < SpinCount_; ++i) {
+                SpinLockPause();
+
+                if (AtomicLoad(Counter_) >= 0)
+                    goto again;
+                if (AtomicLoad(TrappedFutex_) == 1)
+                    goto skip_store_trapped;
+            }
+
+            SequenceStore(TrappedFutex_, 1);
+        skip_store_trapped:
+
+            if (AtomicLoad(Counter_) < 0) {
+                FutexWait(TrappedFutex_, 1);
+                if (AtomicLoad(Counter_) < 0)
+                    goto again;
+            } else if (AtomicLoad(TrappedFutex_)) {
+                SequenceStore(TrappedFutex_, 0);
+                FutexWake(TrappedFutex_, 0x7fffffff);
+            }
+            break;
+        }
+    }
+}
+
+#endif // _linux_