Limit the number of concurrently handled stroke messages.

This avoids clogging the thread pool with potentially blocking jobs.

src/libcharon/plugins/stroke/stroke_socket.c

@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2011 Tobias Brunner
  * Copyright (C) 2008 Martin Willi
  * Hochschule fuer Technik Rapperswil
  *
@@ -25,7 +26,10 @@
 
 #include <hydra.h>
 #include <daemon.h>
+#include <threading/mutex.h>
 #include <threading/thread.h>
+#include <threading/condvar.h>
+#include <utils/linked_list.h>
 #include <processing/jobs/callback_job.h>
 
 #include "stroke_config.h"
@@ -35,6 +39,12 @@
 #include "stroke_attribute.h"
 #include "stroke_list.h"
 
+/**
+ * To avoid clogging the thread pool with (blocking) jobs, we limit the number
+ * of concurrently handled stroke commands.
+ */
+#define MAX_CONCURRENT 4
+
 typedef struct stroke_job_context_t stroke_job_context_t;
 typedef struct private_stroke_socket_t private_stroke_socket_t;
 
@@ -56,7 +66,32 @@ struct private_stroke_socket_t {
 	/**
 	 * job accepting stroke messages
 	 */
-	callback_job_t *job;
+	callback_job_t *receiver;
+
+	/**
+	 * job handling stroke messages
+	 */
+	callback_job_t *handler;
+
+	/**
+	 * queued stroke commands
+	 */
+	linked_list_t *commands;
+
+	/**
+	 * lock for command list
+	 */
+	mutex_t *mutex;
+
+	/**
+	 * condvar to signal the arrival or completion of commands
+	 */
+	condvar_t *condvar;
+
+	/**
+	 * the number of currently handled commands
+	 */
+	u_int handling;
 
 	/**
 	 * configuration backend
@@ -84,7 +119,7 @@ struct private_stroke_socket_t {
 	stroke_ca_t *ca;
 
 	/**
-	 * Status information logging
+	 * status information logging
 	 */
 	stroke_list_t *list;
 };
@@ -488,6 +523,18 @@ static void stroke_job_context_destroy(stroke_job_context_t *this)
 	free(this);
 }
 
+/**
+ * called to signal the completion of a command
+ */
+static inline job_requeue_t job_processed(private_stroke_socket_t *this)
+{
+	this->mutex->lock(this->mutex);
+	this->handling--;
+	this->condvar->signal(this->condvar);
+	this->mutex->unlock(this->mutex);
+	return JOB_REQUEUE_NONE;
+}
+
 /**
  * process a stroke request from the socket pointed by "fd"
  */
@@ -506,7 +553,7 @@ static job_requeue_t process(stroke_job_context_t *ctx)
 	{
 		DBG1(DBG_CFG, "reading length of stroke message failed: %s",
 			 strerror(errno));
-		return JOB_REQUEUE_NONE;
+		return job_processed(this);
 	}
 
 	/* read message */
@@ -515,14 +562,14 @@ static job_requeue_t process(stroke_job_context_t *ctx)
 	if (bytes_read != msg_length)
 	{
 		DBG1(DBG_CFG, "reading stroke message failed: %s", strerror(errno));
-		return JOB_REQUEUE_NONE;
+		return job_processed(this);
 	}
 
 	out = fdopen(strokefd, "w+");
 	if (out == NULL)
 	{
 		DBG1(DBG_CFG, "opening stroke output channel failed: %s", strerror(errno));
-		return JOB_REQUEUE_NONE;
+		return job_processed(this);
 	}
 
 	DBG3(DBG_CFG, "stroke message %b", (void*)msg, msg_length);
@@ -599,11 +646,38 @@ static job_requeue_t process(stroke_job_context_t *ctx)
 	fclose(out);
 	/* fclose() closes underlying FD */
 	ctx->fd = 0;
-	return JOB_REQUEUE_NONE;
+	return job_processed(this);
 }
 
 /**
- * Implementation of private_stroke_socket_t.stroke_receive.
+ * Handle queued stroke commands
+ */
+static job_requeue_t handle(private_stroke_socket_t *this)
+{
+	stroke_job_context_t *ctx;
+	callback_job_t *job;
+	bool oldstate;
+
+	this->mutex->lock(this->mutex);
+	thread_cleanup_push((thread_cleanup_t)this->mutex->unlock, this->mutex);
+	oldstate = thread_cancelability(TRUE);
+	while (this->commands->get_count(this->commands) == 0 ||
+		   this->handling >= MAX_CONCURRENT)
+	{
+		this->condvar->wait(this->condvar, this->mutex);
+	}
+	thread_cancelability(oldstate);
+	this->commands->remove_first(this->commands, (void**)&ctx);
+	this->handling++;
+	thread_cleanup_pop(TRUE);
+	job = callback_job_create_with_prio((callback_job_cb_t)process, ctx,
+			(void*)stroke_job_context_destroy, this->handler, JOB_PRIO_HIGH);
+	lib->processor->queue_job(lib->processor, (job_t*)job);
+	return JOB_REQUEUE_DIRECT;
+}
+
+/**
+ * Accept stroke commands and queue them to be handled
  */
 static job_requeue_t receive(private_stroke_socket_t *this)
 {
@@ -611,7 +685,6 @@ static job_requeue_t receive(private_stroke_socket_t *this)
 	int strokeaddrlen = sizeof(strokeaddr);
 	int strokefd;
 	bool oldstate;
-	callback_job_t *job;
 	stroke_job_context_t *ctx;
 
 	oldstate = thread_cancelability(TRUE);
@@ -624,17 +697,18 @@ static job_requeue_t receive(private_stroke_socket_t *this)
 		return JOB_REQUEUE_FAIR;
 	}
 
-	ctx = malloc_thing(stroke_job_context_t);
+	INIT(ctx,
-	ctx->fd = strokefd;
+		.fd = strokefd,
-	ctx->this = this;
+		.this = this,
-	job = callback_job_create_with_prio((callback_job_cb_t)process,
+	);
-			ctx, (void*)stroke_job_context_destroy, this->job, JOB_PRIO_HIGH);
+	this->mutex->lock(this->mutex);
-	lib->processor->queue_job(lib->processor, (job_t*)job);
+	this->commands->insert_last(this->commands, ctx);
+	this->condvar->signal(this->condvar);
+	this->mutex->unlock(this->mutex);
 
 	return JOB_REQUEUE_FAIR;
 }
 
-
 /**
  * initialize and open stroke socket
  */
@@ -682,7 +756,11 @@ static bool open_socket(private_stroke_socket_t *this)
 METHOD(stroke_socket_t, destroy, void,
 	private_stroke_socket_t *this)
 {
-	this->job->cancel(this->job);
+	this->handler->cancel(this->handler);
+	this->receiver->cancel(this->receiver);
+	this->commands->destroy_function(this->commands, (void*)stroke_job_context_destroy);
+	this->condvar->destroy(this->condvar);
+	this->mutex->destroy(this->mutex);
 	lib->credmgr->remove_set(lib->credmgr, &this->ca->set);
 	lib->credmgr->remove_set(lib->credmgr, &this->cred->set);
 	charon->backends->remove_backend(charon->backends, &this->config->backend);
@@ -722,14 +800,22 @@ stroke_socket_t *stroke_socket_create()
 	this->control = stroke_control_create();
 	this->list = stroke_list_create(this->attribute);
 
+	this->mutex = mutex_create(MUTEX_TYPE_DEFAULT);
+	this->condvar = condvar_create(CONDVAR_TYPE_DEFAULT);
+	this->commands = linked_list_create();
+
 	lib->credmgr->add_set(lib->credmgr, &this->ca->set);
 	lib->credmgr->add_set(lib->credmgr, &this->cred->set);
 	charon->backends->add_backend(charon->backends, &this->config->backend);
 	hydra->attributes->add_provider(hydra->attributes, &this->attribute->provider);
 
-	this->job = callback_job_create_with_prio((callback_job_cb_t)receive,
+	this->receiver = callback_job_create_with_prio((callback_job_cb_t)receive,
 										this, NULL, NULL, JOB_PRIO_CRITICAL);
-	lib->processor->queue_job(lib->processor, (job_t*)this->job);
+	lib->processor->queue_job(lib->processor, (job_t*)this->receiver);
+
+	this->handler = callback_job_create_with_prio((callback_job_cb_t)handle,
+										this, NULL, NULL, JOB_PRIO_CRITICAL);
+	lib->processor->queue_job(lib->processor, (job_t*)this->handler);
 
 	return &this->public;
 }