First atomicity bug example from chapter

threads-bugs/Makefile

@@ -0,0 +1,25 @@
+CC     := gcc
+CFLAGS := -Wall -Werror -I../include -pthread
+
+OS     := $(shell uname -s)
+LIBS   := 
+ifeq ($(OS),Linux)
+	LIBS += -pthread
+endif
+
+SRCS   := atomicity.c 
+
+OBJS   := ${SRCS:c=o}
+PROGS  := ${SRCS:.c=}
+
+.PHONY: all
+all: ${PROGS}
+
+${PROGS} : % : %.o Makefile
+	${CC} $< -o $@ ${LIBS}
+
+clean:
+	rm -f ${PROGS} ${OBJS}
+
+%.o: %.c Makefile
+	${CC} ${CFLAGS} -c $<

threads-bugs/atomicity.c

@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <unistd.h>
+
+#include "common.h"
+#include "common_threads.h"
+
+typedef struct {
+    int pid;
+} proc_t;
+
+typedef struct {
+    proc_t *proc_info;
+} thread_info_t; 
+
+proc_t p;
+thread_info_t th;
+thread_info_t *thd;
+
+void *thread1(void *arg) {
+    printf("t1: before check\n");
+    if (thd->proc_info) {
+	printf("t1: after check\n");
+	sleep(2);
+	printf("t1: use!\n");
+	printf("%d\n", thd->proc_info->pid);
+    }
+    return NULL;
+}
+
+void *thread2(void *arg) {
+    printf("                 t2: begin\n");
+    sleep(1); // change to 5 to make the code "work"...
+    printf("                 t2: set to NULL\n");
+    thd->proc_info = NULL;
+    return NULL;
+}
+
+int main(int argc, char *argv[]) {                    
+    if (argc != 1) {
+	fprintf(stderr, "usage: main\n");
+	exit(1);
+    }
+    thread_info_t t;
+    p.pid = 100;
+    t.proc_info = &p;
+    thd = &t;
+
+    pthread_t p1, p2;
+    printf("main: begin\n");
+    Pthread_create(&p1, NULL, thread1, NULL); 
+    Pthread_create(&p2, NULL, thread2, NULL);
+    // join waits for the threads to finish
+    Pthread_join(p1, NULL); 
+    Pthread_join(p2, NULL); 
+    printf("main: end\n");
+    return 0;
+}
+