syscalls: allow for blocking syscalls

src/include/kernel/syscalls.h

@@ -14,7 +14,7 @@
 #define MAX_SYSCALL                     12       // for now
 
 typedef struct SyscallRequest {
-    bool busy, queued;
+    bool busy, queued, unblock;
 
     uint64_t function;
     uint64_t params[4];

src/syscalls/dispatch.c

@@ -20,18 +20,22 @@ void syscallDispatchExit(SyscallRequest *req) {
 
 void syscallDispatchFork(SyscallRequest *req) {
     req->ret = fork(req->thread);
+    req->unblock = true;
 }
 
 void syscallDispatchYield(SyscallRequest *req) {
     req->ret = yield(req->thread);
+    req->unblock = true;
 }
 
 void syscallDispatchGetPID(SyscallRequest *req) {
     req->ret = req->thread->pid;
+    req->unblock = true;
 }
 
 void syscallDispatchGetTID(SyscallRequest *req) {
     req->ret = req->thread->tid;
+    req->unblock = true;
 }
 
 void syscallDispatchGetUID(SyscallRequest *req) {
@@ -42,6 +46,8 @@ void syscallDispatchGetUID(SyscallRequest *req) {
     } else {
         req->ret = p->user;
     }
+
+    req->unblock = true;
 }
 
 void syscallDispatchGetGID(SyscallRequest *req) {
@@ -52,14 +58,16 @@ void syscallDispatchGetGID(SyscallRequest *req) {
     } else {
         req->ret = p->group;
     }
+
+    req->unblock = true;
 }
 
 void syscallDispatchMSleep(SyscallRequest *req) {
     req->ret = msleep(req->thread, req->params[0]);
 }
 
 void (*syscallDispatchTable[])(SyscallRequest *) = {
-    // group 1: scheduler functions
+    /* group 1: scheduler functions */
     syscallDispatchExit,        // 0 - exit()
     syscallDispatchFork,        // 1 - fork()
     syscallDispatchYield,       // 2 - yield()

src/syscalls/queue.c

@@ -96,7 +96,7 @@ int syscallProcess() {
         platformSetContextStatus(syscall->thread->context, syscall->ret);
     }
 
-    if(syscall->thread->status == THREAD_BLOCKED) {
+    if((syscall->thread->status == THREAD_BLOCKED) && syscall->unblock) {
         // this way we prevent accidentally running threads that exit()
         syscall->thread->status = THREAD_QUEUED;
         syscall->thread->time = schedTimeslice(syscall->thread, syscall->thread->priority);