Refactor shared-spin-lock to use atomic "spinLock"
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dfd1689daa
commit
5c96151a23
2 changed files with 119 additions and 57 deletions
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@ -18,77 +18,121 @@ UDPC::SharedSpinLock::Ptr UDPC::SharedSpinLock::newInstance() {
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UDPC::SharedSpinLock::SharedSpinLock() :
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selfWeakPtr(),
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mutex(),
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spinLock(false),
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read(0),
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write(false)
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{}
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UDPC::LockObj<false> UDPC::SharedSpinLock::spin_read_lock() {
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bool expected;
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while (true) {
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std::lock_guard<std::mutex> lock(mutex);
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if (!write) {
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++read;
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return LockObj<false>(selfWeakPtr, Badge{});
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expected = false;
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if(spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (!write) {
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++read;
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spinLock.store(false, std::memory_order_release);
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return LockObj<false>(selfWeakPtr, Badge{});
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} else {
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spinLock.store(false, std::memory_order_release);
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}
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}
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}
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}
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UDPC::LockObj<false> UDPC::SharedSpinLock::try_spin_read_lock() {
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std::lock_guard<std::mutex> lock(mutex);
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if (!write) {
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++read;
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return LockObj<false>(selfWeakPtr, Badge{});
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bool expected = false;
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if (spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (!write) {
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++read;
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spinLock.store(false, std::memory_order_release);
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return LockObj<false>(selfWeakPtr, Badge{});
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} else {
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spinLock.store(false, std::memory_order_release);
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}
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}
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return LockObj<false>{};
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}
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void UDPC::SharedSpinLock::read_unlock(UDPC::Badge &&badge) {
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if (badge.isValid) {
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std::lock_guard<std::mutex> lock(mutex);
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if (read > 0) {
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--read;
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badge.isValid = false;
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bool expected;
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while (true) {
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expected = false;
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if (spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (read > 0) {
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--read;
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badge.isValid = false;
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}
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spinLock.store(false, std::memory_order_release);
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break;
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}
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}
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}
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}
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UDPC::LockObj<true> UDPC::SharedSpinLock::spin_write_lock() {
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bool expected;
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while (true) {
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std::lock_guard<std::mutex> lock(mutex);
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if (!write && read == 0) {
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write = true;
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return LockObj<true>(selfWeakPtr, Badge{});
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expected = false;
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if (spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (!write && read == 0) {
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write = true;
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spinLock.store(false, std::memory_order_release);
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return LockObj<true>(selfWeakPtr, Badge{});
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} else {
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spinLock.store(false, std::memory_order_release);
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}
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}
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}
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}
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UDPC::LockObj<true> UDPC::SharedSpinLock::try_spin_write_lock() {
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std::lock_guard<std::mutex> lock(mutex);
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if (!write && read == 0) {
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write = true;
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return LockObj<true>(selfWeakPtr, Badge{});
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bool expected = false;
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if (spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (!write && read == 0) {
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write = true;
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spinLock.store(false, std::memory_order_release);
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return LockObj<true>(selfWeakPtr, Badge{});
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} else {
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spinLock.store(false, std::memory_order_release);
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}
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}
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return LockObj<true>{};
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}
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void UDPC::SharedSpinLock::write_unlock(UDPC::Badge &&badge) {
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if (badge.isValid) {
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std::lock_guard<std::mutex> lock(mutex);
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write = false;
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badge.isValid = false;
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bool expected;
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while(true) {
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expected = false;
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if (spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (write) {
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write = false;
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badge.isValid = false;
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}
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spinLock.store(false, std::memory_order_release);
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break;
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}
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}
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}
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}
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UDPC::LockObj<false> UDPC::SharedSpinLock::trade_write_for_read_lock(UDPC::LockObj<true> &lockObj) {
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if (lockObj.isValid() && lockObj.badge.isValid) {
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bool expected;
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while (true) {
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std::lock_guard<std::mutex> lock(mutex);
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if (write && read == 0) {
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read = 1;
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write = false;
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lockObj.isLocked = false;
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lockObj.badge.isValid = false;
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return LockObj<false>(selfWeakPtr, Badge{});
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expected = false;
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if (spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (write && read == 0) {
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read = 1;
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write = false;
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lockObj.isLocked = false;
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lockObj.badge.isValid = false;
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spinLock.store(false, std::memory_order_release);
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return LockObj<false>(selfWeakPtr, Badge{});
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} else {
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spinLock.store(false, std::memory_order_release);
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}
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}
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}
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} else {
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@ -98,13 +142,18 @@ UDPC::LockObj<false> UDPC::SharedSpinLock::trade_write_for_read_lock(UDPC::LockO
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UDPC::LockObj<false> UDPC::SharedSpinLock::try_trade_write_for_read_lock(UDPC::LockObj<true> &lockObj) {
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if (lockObj.isValid() && lockObj.badge.isValid) {
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std::lock_guard<std::mutex> lock(mutex);
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if (write && read == 0) {
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read = 1;
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write = false;
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lockObj.isLocked = false;
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lockObj.badge.isValid = false;
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return LockObj<false>(selfWeakPtr, Badge{});
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bool expected = false;
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if (spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (write && read == 0) {
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read = 1;
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write = false;
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lockObj.isLocked = false;
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lockObj.badge.isValid = false;
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spinLock.store(false, std::memory_order_release);
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return LockObj<false>(selfWeakPtr, Badge{});
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} else {
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spinLock.store(false, std::memory_order_release);
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}
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}
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}
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return LockObj<false>{};
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@ -112,14 +161,20 @@ UDPC::LockObj<false> UDPC::SharedSpinLock::try_trade_write_for_read_lock(UDPC::L
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UDPC::LockObj<true> UDPC::SharedSpinLock::trade_read_for_write_lock(UDPC::LockObj<false> &lockObj) {
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if (lockObj.isValid() && lockObj.badge.isValid) {
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bool expected;
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while (true) {
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std::lock_guard<std::mutex> lock(mutex);
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if (!write && read == 1) {
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read = 0;
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write = true;
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lockObj.isLocked = false;
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lockObj.badge.isValid = false;
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return LockObj<true>(selfWeakPtr, Badge{});
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expected = false;
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if (spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (!write && read == 1) {
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read = 0;
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write = true;
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lockObj.isLocked = false;
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lockObj.badge.isValid = false;
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spinLock.store(false, std::memory_order_release);
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return LockObj<true>(selfWeakPtr, Badge{});
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} else {
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spinLock.store(false, std::memory_order_release);
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}
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}
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}
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} else {
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@ -129,13 +184,18 @@ UDPC::LockObj<true> UDPC::SharedSpinLock::trade_read_for_write_lock(UDPC::LockOb
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UDPC::LockObj<true> UDPC::SharedSpinLock::try_trade_read_for_write_lock(UDPC::LockObj<false> &lockObj) {
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if (lockObj.isValid() && lockObj.badge.isValid) {
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std::lock_guard<std::mutex> lock(mutex);
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if (!write && read == 1) {
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read = 0;
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write = true;
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lockObj.isLocked = false;
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lockObj.badge.isValid = false;
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return LockObj<true>(selfWeakPtr, Badge{});
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bool expected = false;
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if (spinLock.compare_exchange_weak(expected, true, std::memory_order_acquire, std::memory_order_relaxed)) {
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if (!write && read == 1) {
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read = 0;
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write = true;
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lockObj.isLocked = false;
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lockObj.badge.isValid = false;
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spinLock.store(false, std::memory_order_release);
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return LockObj<true>(selfWeakPtr, Badge{});
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} else {
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spinLock.store(false, std::memory_order_release);
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}
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}
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}
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return LockObj<true>{};
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@ -2,7 +2,6 @@
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#define UDPC_CXX11_SHARED_SPIN_LOCK_H_
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#include <memory>
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#include <mutex>
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#include <atomic>
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namespace UDPC {
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@ -75,9 +74,9 @@ public:
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SharedSpinLock(const SharedSpinLock&) = delete;
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SharedSpinLock& operator=(const SharedSpinLock&) = delete;
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// Allow move.
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SharedSpinLock(SharedSpinLock&&) = default;
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SharedSpinLock& operator=(SharedSpinLock&&) = default;
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// Disallow move.
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SharedSpinLock(SharedSpinLock&&) = delete;
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SharedSpinLock& operator=(SharedSpinLock&&) = delete;
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LockObj<false> spin_read_lock();
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LockObj<false> try_spin_read_lock();
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@ -97,7 +96,10 @@ private:
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SharedSpinLock();
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Weak selfWeakPtr;
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std::mutex mutex;
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/// Used to lock the read/write member variables.
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volatile std::atomic_bool spinLock;
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unsigned int read;
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bool write;
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