From 471fdef61e39650a40faa0b4ee16ee8a3ea4f8cb Mon Sep 17 00:00:00 2001
From: Thomas Preud'homme <robotux@celest.fr>
Date: Fri, 12 Jun 2009 00:34:33 +0200
Subject: [PATCH] Bug in communication techniques bench

* producers can finish before consumer and thus free the thread-local
  storage they have which could lead to sigsegv from consumer
---
 communication_techniques/src/main.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/communication_techniques/src/main.c b/communication_techniques/src/main.c
index bceb4a1..3c0ba16 100644
--- a/communication_techniques/src/main.c
+++ b/communication_techniques/src/main.c
@@ -20,6 +20,10 @@ static long nb_prod = 0;
 static long size_buf = 1;
 static char *calculation_lib = NULL;
 static int shared = 0;
+pthread_cond_t cond_cons_has_finished = PTHREAD_COND_INITIALIZER;
+pthread_mutex_t mutex_cons_has_finished = PTHREAD_MUTEX_INITIALIZER;
+static int consumer_has_finished = 0;
+static int producers_ended = 0;
 
 void usage(char *argv[])
 {
@@ -141,10 +145,12 @@ int analyse_options(int argc, char *argv[])
 	return 0;
 }
 
-void *producer(void *unused)
+void *producer(void *cont_ptr_void)
 {
 	int i, j, k;
+	volatile int *cont;
 
+	cont = *((volatile int **) cont_ptr_void);
 	if (shared)
 	{
 		pthread_t tid;
@@ -173,7 +179,16 @@ void *producer(void *unused)
 	}
 	printf("[%p] Producer finished !\n", (void*) pthread_self());
 	remove_sender();
-	/* Threads must wait the consumer because of thread-local storages */
+	/* 
+	 * When a producer end its thread-local storage vanished. Thus,
+	 * producers must finish only after consumer has stopped using them
+	 */
+	pthread_mutex_lock(&mutex_cons_has_finished);
+	if (++producers_ended == nb_prod)
+		*cont = 0;
+	if (!consumer_has_finished)
+		pthread_cond_wait(&cond_cons_has_finished, &mutex_cons_has_finished);
+	pthread_mutex_unlock(&mutex_cons_has_finished);
 	return NULL;
 }
 
@@ -199,6 +214,10 @@ void *receptor(void *a)
 		}
 	}
 	reception(onMessage);
+	pthread_mutex_lock(&mutex_cons_has_finished);
+	consumer_has_finished = 1;
+	pthread_cond_broadcast(&cond_cons_has_finished);
+	pthread_mutex_unlock(&mutex_cons_has_finished);
 	return NULL;
 }
 
@@ -214,11 +233,10 @@ int main(int argc, char *argv[])
 	tid = (pthread_t *) malloc((nb_prod + 1) * sizeof(pthread_t));
 	cont = init_comm();
 	for(i = 0; i < nb_prod; i++)
-		pthread_create(&tid[i], NULL, producer, NULL);
+		pthread_create(&tid[i], NULL, producer, &cont);
 	pthread_create(&tid[i], NULL, receptor, NULL);
 	for(i = 0; i < nb_prod; i++)
 		pthread_join(tid[i], &return_value);
-	*cont = 0;
 	pthread_join(tid[i], &return_value);
 	free(tid);
 	return EXIT_SUCCESS;