Initial revision

lang/occam/lib/par.c

@@ -0,0 +1,92 @@
+/*	par.c - Routines to simulate parallelism */
+#include "process.h"
+
+static void search_next(), DEADLOCK();
+
+void resumenext()
+/* Stops the current process, by saving its stack,  and determines a new one
+ * to restart. In case the root of the process tree is passed more then once,
+ * without a process  having done something useful, we'll have a deadlock.
+ */
+{
+	if (group!=nil) {
+		register struct process *proc= *group->active;
+		register wordsize size;
+
+		size=top_size(group->s_brk);
+		proc->stack=alloc((unsigned) size);
+
+		if (top_save(size, proc->stack)) {
+			group->active= &proc->next;
+			search_next();
+		} else {
+			free(proc->stack);
+			load_betweens();
+		}
+	} else
+		if (++deadlock>1) DEADLOCK();
+}
+
+static void search_next()
+/* Tries to resume the active process, if this is not possible, the process
+ * tree will be searched for another process. If the process tree is fully
+ * traversed, search will restart at the root of the tree.
+ */
+{
+	while (*group->active==nil && group->up!=nil) {
+		save_between(group);
+
+		group=group->up;
+
+		group->active= &(*group->active)->next;
+	}
+
+	if (*group->active==nil) {
+		if (++deadlock>1) DEADLOCK();
+		group->active= &group->first;
+	}
+
+	highest_group=group;
+
+	while ((*group->active)->down!=nil) {
+		group=(*group->active)->down;
+		group->active= &group->first;
+	}
+	top_load((*group->active)->stack);
+}
+
+void parend()
+/* Deletes the current process from its process group and searches for a new
+ * process to run. The entire group is removed if this is the last process in
+ * the group, execution then continues with the process that set up this group
+ * in the first place.
+ */
+{
+	register struct process *junk;
+
+	junk= *group->active;
+	*group->active=junk->next;
+	free((void *) junk);
+
+	if (group->first==nil) {
+		register struct procgroup *junk;
+
+		delete_between(group);
+
+		junk=group;
+		group=group->up;
+		free((void *) junk);
+
+		if (group!=nil)
+			(*group->active)->down=nil;
+	} else {
+		deadlock=0;
+		search_next();
+	}
+}
+
+static void DEADLOCK()
+{
+	write(2, "DEADLOCK\n", 9);
+	abort();
+}