From 84734e5c8d2797f876b3b5617fbbfd812970d4b4 Mon Sep 17 00:00:00 2001
From: Florian Fischer <florian.fl.fischer@fau.de>
Date: Tue, 16 Feb 2021 18:16:08 +0100
Subject: [PATCH] [IO] replace the std::mutex.try_lock with our own std::atomic
implementation
---
emper/io/IoContext.cpp | 4 ++--
emper/io/IoContext.hpp | 7 +++----
emper/lib/adt/AtomicTryLock.hpp | 25 +++++++++++++++++++++++++
3 files changed, 30 insertions(+), 6 deletions(-)
create mode 100644 emper/lib/adt/AtomicTryLock.hpp
diff --git a/emper/io/IoContext.cpp b/emper/io/IoContext.cpp
index 6768524f..90a59923 100644
--- a/emper/io/IoContext.cpp
+++ b/emper/io/IoContext.cpp
@@ -179,7 +179,7 @@ template void IoContext::submit<CallerEnvironment::ANYWHERE>(Future &future);
template <CallerEnvironment callerEnvironment>
void IoContext::reapCompletions() {
// Someone else is currently reaping completions
- if (unlikely(!cq_mutex.try_lock())) {
+ if (unlikely(!cq_lock.try_lock())) {
return;
}
@@ -254,7 +254,7 @@ void IoContext::reapCompletions() {
}
unlock:
- cq_mutex.unlock();
+ cq_lock.unlock();
}
// Show the compiler our template incarnations
diff --git a/emper/io/IoContext.hpp b/emper/io/IoContext.hpp
index 37081f41..4031c963 100644
--- a/emper/io/IoContext.hpp
+++ b/emper/io/IoContext.hpp
@@ -11,13 +11,13 @@
#include <cstdint> // for uint64_t
#include <functional> // for less
#include <memory> // for allocator
-#include <mutex> // for mutex
#include "CallerEnvironment.hpp" // for CallerEnvironment, EMPER
#include "Debug.hpp" // for LogSubsystem, LogSubsystem::IO, Logger
#include "Runtime.hpp" // for Runtime
#include "emper-config.h" // for EMPER_IO_WORKER_URING_ENTRIES
#include "io/Stats.hpp" // for Stats
+#include "lib/adt/AtomicTryLock.hpp"
#include "lib/adt/LockedSet.hpp" // for LockedSet
namespace emper::io {
@@ -44,9 +44,8 @@ class IoContext : public Logger<LogSubsystem::IO> {
// to the global IoContext
static void startGlobalCompleter(IoContext &globalIo);
- // Mutex protecting the completion queue of ring.
- // It is used with try_lock() in reapCompletions.
- std::mutex cq_mutex;
+ // TryLock protecting the completion queue of ring.
+ lib::adt::AtomicTryLock cq_lock;
struct io_uring ring;
// eventfd registered with ring.
diff --git a/emper/lib/adt/AtomicTryLock.hpp b/emper/lib/adt/AtomicTryLock.hpp
new file mode 100644
index 00000000..222d80e7
--- /dev/null
+++ b/emper/lib/adt/AtomicTryLock.hpp
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// Copyright © 2020 Florian Fischer
+#pragma once
+
+#include <atomic>
+
+#include "Common.hpp"
+
+namespace emper::lib::adt {
+
+class ALIGN_TO_CACHE_LINE AtomicTryLock {
+ private:
+ std::atomic<bool> locked;
+
+ public:
+ AtomicTryLock(bool locked = false) : locked(locked) {}
+
+ auto try_lock() -> bool {
+ bool previously_locked = locked.exchange(true, std::memory_order_acquire);
+ return !previously_locked;
+ }
+
+ void unlock() { locked.store(false, std::memory_order_release); }
+};
+} // namespace emper::lib::adt
--
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