From 54c80c739981ed5b327dd4860022b866a07fdf18 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?I=C3=B1aki=20Baz=20Castillo?= <ibc@aliax.net>
Date: Fri, 9 Aug 2024 13:14:22 +0200
Subject: [PATCH] DepLibUring improvements

### Details

- Be explicit. Always check if liburing is supported before calling any method in `DepLibUring`.  This is cosmetic but helps when reading the whole code.
---
 worker/include/DepLibUring.hpp | 11 +++++--
 worker/src/DepLibUring.cpp     | 56 +++++++++++++++++++---------------
 2 files changed, 41 insertions(+), 26 deletions(-)

diff --git a/worker/include/DepLibUring.hpp b/worker/include/DepLibUring.hpp
index 973acaff42..7c8f0357c3 100644
--- a/worker/include/DepLibUring.hpp
+++ b/worker/include/DepLibUring.hpp
@@ -33,9 +33,10 @@ class DepLibUring
 
 	using SendBuffer = uint8_t[SendBufferSize];
 
-	static bool IsRuntimeSupported();
 	static void ClassInit();
 	static void ClassDestroy();
+	static void CheckRuntimeSupport();
+	static bool IsRuntimeSupported();
 	static flatbuffers::Offset<FBS::LibUring::Dump> FillBuffer(flatbuffers::FlatBufferBuilder& builder);
 	static void StartPollingCQEs();
 	static void StopPollingCQEs();
@@ -51,8 +52,10 @@ class DepLibUring
 	class LibUring;
 
 	thread_local static LibUring* liburing;
+	static bool runtimeSupported{ false };
 
-public:
+private:
+	// Private singleton.
 	class LibUring
 	{
 	public:
@@ -98,6 +101,10 @@ class DepLibUring
 		}
 
 	private:
+		void SetInactive()
+		{
+			this->active = false;
+		}
 		UserData* GetUserData();
 		bool IsDataInSendBuffers(const uint8_t* data) const
 		{
diff --git a/worker/src/DepLibUring.cpp b/worker/src/DepLibUring.cpp
index 95d2b6631e..ee64880c5e 100644
--- a/worker/src/DepLibUring.cpp
+++ b/worker/src/DepLibUring.cpp
@@ -114,29 +114,6 @@ inline static void onFdEvent(uv_poll_t* handle, int status, int events)
 
 /* Static class methods */
 
-bool DepLibUring::IsRuntimeSupported()
-{
-	// clang-format off
-	struct utsname buffer{};
-	// clang-format on
-
-	auto err = uname(std::addressof(buffer));
-
-	if (err != 0)
-	{
-		MS_THROW_ERROR("uname() failed: %s", std::strerror(err));
-	}
-
-	MS_DEBUG_TAG(info, "kernel version: %s", buffer.version);
-
-	auto* kernelMayorCstr = buffer.release;
-	auto kernelMayorLong  = strtol(kernelMayorCstr, &kernelMayorCstr, 10);
-
-	// liburing `sento` capabilities are supported for kernel versions greather
-	// than or equal to 6.
-	return kernelMayorLong >= 6;
-}
-
 void DepLibUring::ClassInit()
 {
 	const auto mayor = io_uring_major_version();
@@ -144,6 +121,9 @@ void DepLibUring::ClassInit()
 
 	MS_DEBUG_TAG(info, "liburing version: \"%i.%i\"", mayor, minor);
 
+	// This must be called first.
+	DepLibUring::CheckRuntimeSupport();
+
 	if (DepLibUring::IsRuntimeSupported())
 	{
 		DepLibUring::liburing = new LibUring();
@@ -163,6 +143,34 @@ void DepLibUring::ClassDestroy()
 	delete DepLibUring::liburing;
 }
 
+void DepLibUring::CheckRuntimeSupport()
+{
+	// clang-format off
+	struct utsname buffer{};
+	// clang-format on
+
+	auto err = uname(std::addressof(buffer));
+
+	if (err != 0)
+	{
+		MS_THROW_ERROR("uname() failed: %s", std::strerror(err));
+	}
+
+	MS_DEBUG_TAG(info, "kernel version: %s", buffer.version);
+
+	auto* kernelMayorCstr = buffer.release;
+	auto kernelMayorLong  = strtol(kernelMayorCstr, &kernelMayorCstr, 10);
+
+	// liburing `sento` capabilities are supported for kernel versions greather
+	// than or equal to 6.
+	DepLibUring::runtimeSupported = kernelMayorLong >= 6;
+}
+
+bool DepLibUring::IsRuntimeSupported()
+{
+	return DepLibUring::runtimeSupported;
+}
+
 flatbuffers::Offset<FBS::LibUring::Dump> DepLibUring::FillBuffer(flatbuffers::FlatBufferBuilder& builder)
 {
 	MS_TRACE();
@@ -580,7 +588,7 @@ void DepLibUring::LibUring::Submit()
 	MS_TRACE();
 
 	// Unset active flag.
-	this->active = false;
+	SetInactive();
 
 	auto err = io_uring_submit(std::addressof(this->ring));