Use SysV semaphores to implement NamedEvent on Linux

1 files changed, 7 insertions, 100 deletions

diff --git a/zencore/thread.cpp b/zencore/thread.cpp
index 97d44e733..de8b5f515 100644
--- a/zencore/thread.cpp
+++ b/zencore/thread.cpp
@@ -27,19 +27,12 @@
 #	include <pthread.h>
 #	include <signal.h>
 #	include <sys/file.h>
+#	include <sys/sem.h>
 #	include <sys/wait.h>
 #	include <time.h>
 #	include <unistd.h>
 #endif
 
-#if ZEN_PLATFORM_LINUX
-#	include <mqueue.h>
-#endif
-
-#if ZEN_PLATFORM_MAC
-#	include <sys/sem.h>
-#endif
-
 #include <thread>
 
 ZEN_THIRD_PARTY_INCLUDES_START
@@ -249,17 +242,6 @@ Event::Wait(int TimeoutMs)
 
 //////////////////////////////////////////////////////////////////////////
 
-#if ZEN_PLATFORM_LINUX
-static bool
-IsMessageQueueEmpty(int Fd)
-{
-	// Check if there is already a message in the queue.
-	mq_attr Attributes = {O_NONBLOCK, 1, 1, 0};
-	mq_getattr(Fd, &Attributes);
-	return (Attributes.mq_curmsgs == 0);
-}
-#endif	// ZEN_PLATFORM_LINUX
-
 NamedEvent::NamedEvent(std::string_view EventName)
 {
 #if ZEN_PLATFORM_WINDOWS
@@ -270,39 +252,7 @@ NamedEvent::NamedEvent(std::string_view EventName)
 	Name << EventName;
 
 	m_EventHandle = CreateEventA(nullptr, true, false, Name.c_str());
-#elif ZEN_PLATFORM_LINUX
-	ExtendableStringBuilder<64> Name;
-	Name << "/";
-	Name << EventName;
-
-	mq_attr Attributes = {
-		0,	// flags
-		1,	// max message count
-		1,	// max message size
-		0,	// current messages
-	};
-
-	int Inner = mq_open(Name.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0644, &Attributes);
-	if (Inner < 0)
-	{
-		ThrowLastError("Failed to get message queue from mq_open()");
-	}
-
-	int LockResult = flock(Inner, LOCK_EX | LOCK_NB);
-	if (LockResult == 0)
-	{
-		// This isn't really thread safe as the message queue could be set
-		// between getting the exclusive lock and checking the queue. But for
-		// the our simple synchronising of process, this should be okay.
-		while (!IsMessageQueueEmpty(Inner))
-		{
-			char Sink;
-			mq_receive(Inner, &Sink, sizeof(Sink), nullptr);
-		}
-	}
-
-	m_EventHandle = (void*)intptr_t(Inner);
-#elif ZEN_PLATFORM_MAC
+#elif ZEN_PLATFORM_LINUX || ZEN_PLATFORM_MAC
 	// Create a file to back the semaphore
 	ExtendableStringBuilder<64> EventPath;
 	EventPath << "/tmp/" << EventName;
@@ -365,18 +315,7 @@ NamedEvent::Close()
 
 #if ZEN_PLATFORM_WINDOWS
 	CloseHandle(m_EventHandle);
-#elif ZEN_PLATFORM_LINUX
-	int Inner = int(intptr_t(m_EventHandle));
-
-	if (flock(Inner, LOCK_EX | LOCK_NB) == 0)
-	{
-		flock(Inner, LOCK_UN | LOCK_NB);
-		std::filesystem::path Name = PathFromHandle((void*)(intptr_t(Inner)));
-		mq_unlink(Name.c_str());
-	}
-
-	close(Inner);
-#elif ZEN_PLATFORM_MAC
+#elif ZEN_PLATFORM_LINUX || ZEN_PLATFORM_MAC
 	int Fd = int(intptr_t(m_EventHandle) & 0xffff'ffff);
 
 	if (flock(Fd, LOCK_EX | LOCK_NB) == 0)
@@ -400,20 +339,7 @@ NamedEvent::Set()
 {
 #if ZEN_PLATFORM_WINDOWS
 	SetEvent(m_EventHandle);
-#elif ZEN_PLATFORM_LINUX
-	int Inner = int(intptr_t(m_EventHandle));
-
-	if (!IsMessageQueueEmpty(Inner))
-	{
-		return;
-	}
-
-	char Message = 0x49;
-	if (mq_send(Inner, &Message, sizeof(Message), 0) != 0)
-	{
-		ThrowLastError("Unable to send set message to queue");
-	}
-#elif ZEN_PLATFORM_MAC
+#elif ZEN_PLATFORM_LINUX || ZEN_PLATFORM_MAC
 	int Sem = int(intptr_t(m_EventHandle) >> 32);
 	semctl(Sem, 0, SETVAL, 0);
 #endif
@@ -434,25 +360,7 @@ NamedEvent::Wait(int TimeoutMs)
 	}
 
 	return (Result == WAIT_OBJECT_0);
-#elif ZEN_PLATFORM_LINUX
-	int Inner = int(intptr_t(m_EventHandle));
-
-	if (!IsMessageQueueEmpty(Inner))
-	{
-		return true;
-	}
-
-	struct timeval TimeoutValue = {
-		.tv_sec	 = (TimeoutMs >> 10),
-		.tv_usec = (TimeoutMs & 0x3ff) << 10,
-	};
-	struct timeval* TimeoutPtr = (TimeoutMs < 0) ? nullptr : &TimeoutValue;
-
-	fd_set FdSet;
-	FD_ZERO(&FdSet);
-	FD_SET(Inner, &FdSet);
-	return select(Inner + 1, &FdSet, nullptr, nullptr, TimeoutPtr) > 0;
-#elif ZEN_PLATFORM_MAC
+#elif ZEN_PLATFORM_LINUX || ZEN_PLATFORM_MAC
 	int Sem = int(intptr_t(m_EventHandle) >> 32);
 
 	int Result;
@@ -469,8 +377,7 @@ NamedEvent::Wait(int TimeoutMs)
 		.tv_sec	 = TimeoutMs >> 10,
 		.tv_nsec = (TimeoutMs & 0x3ff) << 20,
 	};
-	int Result = semtimedop(Sem, &SemOp, 1, &TimeoutValue);
-	return Result == 0;
+	Result = semtimedop(Sem, &SemOp, 1, &TimeoutValue);
 #else
 	const int SleepTimeMs = 10;
 	SemOp.sem_flg = IPC_NOWAIT;
@@ -486,9 +393,9 @@ NamedEvent::Wait(int TimeoutMs)
 		TimeoutMs -= SleepTimeMs;
 	}
 	while (TimeoutMs > 0);
+#endif // _GNU_SOURCE
 
 	return Result == 0;
-#endif // _GNU_SOURCE
 #endif
 }