syscalls: waitpid

kernel-src/sys/syscalls/waitpid.c

@@ -0,0 +1,77 @@
+#include <kernel/syscalls.h>
+#include <kernel/abi.h>
+#include <arch/cpu.h>
+#include <errno.h>
+#include <logging.h>
+
+syscallret_t syscall_waitpid(context_t *context, pid_t pid, int *status, int options) {
+	syscallret_t ret = {
+		.ret = -1
+	};
+
+	// TODO address check
+	// TODO implement these
+	__assert(options == 0);
+	__assert(pid == -1 || pid > 0);
+
+	thread_t *thread = _cpu()->thread;
+	proc_t *proc = thread->proc;
+	spinlock_acquire(&proc->lock);
+
+	proc_t *prev = NULL;
+	proc_t *iterator = proc->child;
+	proc_t *desired = NULL;
+
+	for (;;) {
+		if (iterator == NULL) {
+			if (pid > 0 && desired == NULL) {
+				ret.errno = ECHILD;
+				spinlock_release(&proc->lock);
+				return ret;
+			}
+			spinlock_release(&proc->lock);
+			if (semaphore_wait(&proc->waitsem, true)) {
+				ret.errno = EINTR;
+				return ret;
+			}
+			spinlock_acquire(&proc->lock);
+			prev = NULL;
+			iterator = proc->child;
+			desired = NULL; // set as null to be certain another thread didn't get it
+			continue;
+		}
+
+		if (pid > 0 && iterator->pid == pid)
+			desired = iterator;
+
+		if (iterator->state == SCHED_PROC_STATE_ZOMBIE)
+			break;
+
+		prev = iterator;
+		iterator = iterator->sibling;
+	}
+
+	// iterator has the zombie child
+
+	if (prev)
+		prev->sibling = iterator->sibling;
+	else
+		proc->child = iterator->sibling;
+
+	spinlock_release(&proc->lock);
+
+	// TODO memory safe operation
+	if (status)
+		*status = iterator->status;
+
+	for (int i = 0; i < iterator->threadtablesize; ++i) {
+		if (iterator->threads[i] == NULL)
+			continue;
+		sched_destroythread(iterator->threads[i]);
+	}
+
+	ret.ret = iterator->pid;
+	ret.errno = 0;
+	sched_destroyproc(iterator);
+	return ret;
+}