core/process.c

@@ -191,3 +191,39 @@ pid_t processGetId(struct process *proc){
 pid_t processGetNextTid(struct process *proc){
     return proc->nextTid++;
 }
+
+//Should be called with IRQ disabled
+struct thread *processGetThread(struct process *proc, pid_t tid)
+{
+    int count;
+    struct thread *th;
+    struct thread *thFound = NULL;
+
+    list_foreach_named(proc->thList, th, count, prevInProcess, nextInProcess)
+    {
+        if (th->tid == tid) {
+            thFound = th;
+            break;
+        }
+    }
+    return thFound;
+}
+
+int processJoinThread(struct process *proc, pid_t tid)
+{
+    uint32_t flags;
+    struct thread *th;
+    int ret = -1;
+
+    disable_IRQs(flags);
+
+    th = processGetThread(proc, tid);
+    if (th && th->wqExit) {
+        wait(th->wqExit);
+        ret = 0;
+    }
+
+    restore_IRQs(flags);
+
+    return ret;
+}

core/process.h

@@ -22,3 +22,4 @@ struct uAddrSpace *processGetAddrSpace(struct process *proc);
 int processInitHeap(struct process *proc, uaddr_t lastUserAddr);
 pid_t processGetId(struct process *proc);
 pid_t processGetNextTid(struct process *proc);
+int processJoinThread(struct process *proc, pid_t tid);

core/syscall.c

@@ -172,11 +172,20 @@ int syscallExecute(int syscallId, const struct cpu_state *userCtx)
             break;
         }
         case SYSCALL_ID_GETPID: {
-            ret        = processGetId(getCurrentThread()->process);
+            ret = processGetId(getCurrentThread()->process);
             break;
         }
         case SYSCALL_ID_GETTID: {
-            ret        = threadGetId(getCurrentThread());
+            ret = threadGetId(getCurrentThread());
+            break;
+        }
+        case SYSCALL_ID_THREAD_JOIN: {
+            thread_id_t tid;
+
+            ret = syscallGet1arg(userCtx, (unsigned int *)&tid);
+            if (ret)
+                break;
+            ret = processJoinThread(getCurrentThread()->process, tid); 
             break;
         }
         default:

core/syscall.h

@@ -15,6 +15,7 @@
 #define SYSCALL_ID_USLEEP 10
 #define SYSCALL_ID_GETPID 11
 #define SYSCALL_ID_GETTID 12
+#define SYSCALL_ID_THREAD_JOIN 13
 
 #ifdef __KERNEL__
 int syscallExecute(int syscallId, const struct cpu_state *user_ctx);

core/thread.c

@@ -89,8 +89,9 @@ struct thread *threadCreate(const char *name, cpu_kstate_function_arg1_t func, v
                         (cpu_kstate_function_arg1_t *)threadExit, 0))
         goto free_mem;
 
-    thread->state = READY;
-    thread->tid = nextTid++;
+    thread->state  = READY;
+    thread->tid    = nextTid++;
+    thread->wqExit = NULL;
     uint32_t flags;
     disable_IRQs(flags);
     list_add_tail(currentThread, thread);
@@ -117,6 +118,14 @@ struct thread *threadCreateUser(const char *name, struct process *proc, uaddr_t
     }
     thread->stackSize = THREAD_DEFAULT_STACK_SIZE;
 
+    thread->wqExit = (struct wait_queue * )malloc(sizeof(struct wait_queue));
+    if (!thread->wqExit) {
+        free((void *)thread->stackAddr);
+        free(thread);
+        return NULL;
+    }
+    waitQueueInit(thread->wqExit);
+
     if (name)
         strzcpy(thread->name, name, THREAD_NAME_MAX_LENGTH);
     else
@@ -151,6 +160,10 @@ void threadDelete(struct thread *thread)
     restore_IRQs(flags);
     assert(thread->state == EXITING);
 
+    if (thread->wqExit) {
+        waitUp(thread->wqExit);
+    }
+
     if (thread->squattedContext) {
         threadChangeCurrentContext(NULL);
     }

core/thread.h

@@ -4,6 +4,7 @@ struct thread;
 #include "cpu_context.h"
 #include "mem.h"
 #include "process.h"
+#include "wait.h"
 
 #define THREAD_NAME_MAX_LENGTH 32
 #define THREAD_DEFAULT_STACK_SIZE PAGE_SIZE
@@ -35,6 +36,7 @@ struct thread {
     // For User thread only
     struct thread *nextInProcess, *prevInProcess;
     struct process *process;
+    struct wait_queue *wqExit; // This will be signaled at thread exit (user only)
 
   /**
    * Address space currently "squatted" by the thread, or used to be

userspace/kernel/syscall.h

@@ -15,6 +15,7 @@
 #define SYSCALL_ID_USLEEP 10
 #define SYSCALL_ID_GETPID 11
 #define SYSCALL_ID_GETTID 12
+#define SYSCALL_ID_THREAD_JOIN 13
 
 #ifdef __KERNEL__
 int syscallExecute(int syscallId, const struct cpu_state *user_ctx);

userspace/libc.c

@@ -807,6 +807,12 @@ int thread_create(pthread_t *thread, start_routine *func, void *arg, size_t stac
                     (unsigned int)arg, stackSize);
 }
 
+int thread_join(pthread_t thread, void **retval){
+    (void)retval;
+    return syscall1(SYSCALL_ID_THREAD_JOIN, (unsigned int)thread);
+}
+
+
 int usleep(useconds_t usec) {
     return syscall1(SYSCALL_ID_USLEEP, (unsigned int)usec);
 }

userspace/main_user.c

@@ -124,14 +124,15 @@ int func_munmap()
 static void *print_hello(void *arg) {
         (void)arg;
         printf("Hello World from thread %lu\n", gettid());
-        usleep(100);
 
         return NULL;
 }
 
 int func_thread() {
         pthread_t id;
+        void *retval;
         thread_create(&id, print_hello, NULL, 4096);
+        thread_join(id, &retval);
 
         return 0;
 }
@@ -163,7 +164,10 @@ int main(int argc, char *argv[]) {
                         continue;
                 }
                 if (strcmp(buf, "tiny") == 0) {
-                        func_tiny();
+                        pthread_t id;
+                        void *retval;
+                        thread_create(&id, func_tiny, NULL, 4096);
+                        thread_join(id, &retval);
                         continue;
                 }
                 if (strcmp(buf, "mmap") == 0) {

userspace/thread.h

@@ -4,3 +4,5 @@
 typedef unsigned long int pthread_t;
 typedef void *(start_routine)(void *);
 int thread_create(pthread_t *thread, start_routine *func, void *arg, size_t stackSize);
+/* retval is ignored ATM */
+int thread_join(pthread_t thread, void **retval);

userspace/tiny.c

@@ -282,8 +282,9 @@ void run()
 
 /* Main program. */
 
-int func_tiny()
+void * func_tiny(void *args)
 {
+  (void)args;
     printf("Enter your program then ESC\n\n");
     printf("TinyC grammar\n");
     printf("<program> ::= <statement>\n");

userspace/tiny.h

@@ -1,4 +1,4 @@
 #pragma once
 
 
-int func_tiny();
+void * func_tiny(void *args);