From 84f93cf7b7768cbf522c75c4e3fe204cf6fd785c Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Mon, 5 Jan 2015 14:17:49 +0100
Subject: [SERVER] Use a thread pool for client connections

---
 src/server/threadpool.c | 108 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 src/server/threadpool.c

(limited to 'src/server/threadpool.c')

diff --git a/src/server/threadpool.c b/src/server/threadpool.c
new file mode 100644
index 0000000..04a8e86
--- /dev/null
+++ b/src/server/threadpool.c
@@ -0,0 +1,108 @@
+#include "globals.h"
+#include "helper.h"
+#include "threadpool.h"
+#include "signal.h"
+#include "locks.h"
+#include <pthread.h>
+
+
+typedef struct _entry_t {
+	struct _entry_t *next;
+	pthread_t thread;
+	int signalFd;
+	void *(*startRoutine)(void *);
+	void * volatile arg;
+} entry_t;
+
+static void *threadpool_worker(void *entryPtr);
+
+static pthread_attr_t threadAttrs;
+
+static int maxIdleThreads = -1;
+static entry_t *pool = NULL;
+static pthread_spinlock_t poolLock;
+
+bool threadpool_init(int maxIdle)
+{
+	if ( maxIdle < 0 || maxIdleThreads >= 0 ) return false;
+	maxIdleThreads = maxIdle;
+	spin_init( &poolLock, PTHREAD_PROCESS_PRIVATE );
+	pthread_attr_init( &threadAttrs );
+	pthread_attr_setdetachstate( &threadAttrs, PTHREAD_CREATE_DETACHED );
+	return true;
+}
+
+bool threadpool_run(void *(*startRoutine)(void *), void *arg)
+{
+	spin_lock( &poolLock );
+	entry_t *entry = pool;
+	if ( entry != NULL ) pool = entry->next;
+	spin_unlock( &poolLock );
+	if ( entry == NULL ) {
+		entry = (entry_t*)malloc( sizeof(entry_t) );
+		entry->signalFd = signal_new();
+		if ( entry->signalFd < 0 ) {
+			printf( "[WARNING] Could not create signalFd for new thread pool thread\n" );
+			return false;
+		}
+		if ( 0 != thread_create( &(entry->thread), &threadAttrs, threadpool_worker, (void*)entry ) ) {
+			printf( "[WARNING] Could not create new thread for thread pool\n" );
+			signal_close( entry->signalFd );
+			free( entry );
+			return false;
+		}
+		printf( "[DEBUG] Thread created!\n" );
+	}
+	entry->next = NULL;
+	entry->startRoutine = startRoutine;
+	entry->arg = arg;
+	signal_call( entry->signalFd );
+	return true;
+}
+
+/**
+ * This is a worker thread of our thread pool.
+ */
+static void *threadpool_worker(void *entryPtr)
+{
+	blockNoncriticalSignals();
+	entry_t *entry = (entry_t*)entryPtr;
+	while ( !_shutdown ) {
+		// Wait for signal from outside that we have work to do
+		int ret = signal_wait( entry->signalFd, -1 );
+		if ( ret > 0 ) {
+			if ( entry->startRoutine == NULL ) {
+				printf( "[DEBUG] Worker woke up but has no work to do!\n" );
+				continue;
+			}
+			// Start assigned work
+			(*entry->startRoutine)( entry->arg );
+			// Reset vars for safety
+			entry->startRoutine = NULL;
+			entry->arg = NULL;
+			// Put thread back into pool if there are less than maxIdleThreds threads, just die otherwise
+			int threadCount = 0;
+			spin_lock( &poolLock );
+			entry_t *ptr = pool;
+			while ( ptr != NULL ) {
+				threadCount++;
+				ptr = ptr->next;
+			}
+			if ( threadCount >= maxIdleThreads ) {
+				spin_unlock( &poolLock );
+				signal_close( entry->signalFd );
+				free( entry );
+				printf(" [DEBUG] Thread killed!\n" );
+				return NULL;
+			}
+			entry->next = pool;
+			pool = entry;
+			spin_unlock( &poolLock );
+			setThreadName( "[pool]" );
+		} else {
+			printf( "[DEBUG] Unexpected return value %d for signal_wait in threadpool worker!\n", ret );
+		}
+	}
+	return NULL;
+}
+
-- 
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