From 6c6615337251e0d74ac941b5d6cab3782a939ce3 Mon Sep 17 00:00:00 2001
From: Nekotekina <nekotekina@gmail.com>
Date: Tue, 3 Mar 2020 16:36:59 +0300
Subject: [PATCH] Threads: move linux m_timer to static thread_local variable

Allows lazy allocation of the timer handle.
---
 Utilities/Thread.cpp | 48 +++++++++++++++++++++++++++-----------------
 Utilities/Thread.h   |  5 -----
 2 files changed, 30 insertions(+), 23 deletions(-)

diff --git a/Utilities/Thread.cpp b/Utilities/Thread.cpp
index e4744bf655..b4da25526c 100644
--- a/Utilities/Thread.cpp
+++ b/Utilities/Thread.cpp
@@ -1800,14 +1800,6 @@ void thread_base::initialize(bool(*wait_cb)(const void*))
 	name.resize(std::min<std::size_t>(15, name.size()));
 	pthread_setname_np(pthread_self(), name.c_str());
 #endif
-
-#ifdef __linux__
-	m_timer = timerfd_create(CLOCK_MONOTONIC, 0);
-	if (m_timer == -1)
-	{
-		sig_log.error("Linux timer allocation failed, use wait_unlock() only");
-	}
-#endif
 }
 
 void thread_base::notify_abort() noexcept
@@ -1823,13 +1815,6 @@ bool thread_base::finalize(int) noexcept
 	// Report pending errors
 	error_code::error_report(0, 0, 0, 0);
 
-#ifdef __linux__
-	if (m_timer != -1)
-	{
-		close(m_timer);
-	}
-#endif
-
 #ifdef _WIN32
 	ULONG64 cycles{};
 	QueryThreadCycleTime(GetCurrentThread(), &cycles);
@@ -1892,7 +1877,34 @@ void thread_ctrl::_wait_for(u64 usec, bool alert /* true */)
 	auto _this = g_tls_this_thread;
 
 #ifdef __linux__
-	if (!alert && _this->m_timer != -1 && usec > 0 && usec <= 1000)
+	static thread_local struct linux_timer_handle_t
+	{
+		// Allocate timer only if needed (i.e. someone calls _wait_for with alert and short period)
+		const int m_timer = timerfd_create(CLOCK_MONOTONIC, 0);
+
+		linux_timer_handle_t() noexcept
+		{
+			if (m_timer == -1)
+			{
+				sig_log.error("Linux timer allocation failed, using the fallback instead.");
+			}
+		}
+
+		operator int() const
+		{
+			return m_timer;
+		}
+
+		~linux_timer_handle_t()
+		{
+			if (m_timer != -1)
+			{
+				close(m_timer);
+			}
+		}
+	} fd_timer;
+
+	if (!alert && usec > 0 && usec <= 1000 && fd_timer != -1)
 	{
 		struct itimerspec timeout;
 		u64 missed;
@@ -1902,8 +1914,8 @@ void thread_ctrl::_wait_for(u64 usec, bool alert /* true */)
 		timeout.it_value.tv_sec = nsec / 1000000000ull;
 		timeout.it_interval.tv_sec = 0;
 		timeout.it_interval.tv_nsec = 0;
-		timerfd_settime(_this->m_timer, 0, &timeout, NULL);
-		if (read(_this->m_timer, &missed, sizeof(missed)) != sizeof(missed))
+		timerfd_settime(fd_timer, 0, &timeout, NULL);
+		if (read(fd_timer, &missed, sizeof(missed)) != sizeof(missed))
 			sig_log.error("timerfd: read() failed");
 		return;
 	}
diff --git a/Utilities/Thread.h b/Utilities/Thread.h
index 2e3f4afd6a..d32a6f51c2 100644
--- a/Utilities/Thread.h
+++ b/Utilities/Thread.h
@@ -97,11 +97,6 @@ class thread_base
 	using native_entry = void*(*)(void* arg);
 #endif
 
-#ifdef __linux__
-	// Linux thread timer
-	int m_timer = -1;
-#endif
-
 	// Thread handle (platform-specific)
 	atomic_t<std::uintptr_t> m_thread{0};