1 files changed, 139 insertions, 0 deletions
diff --git a/src/lib/child-wait.c b/src/lib/child-wait.c
new file mode 100644
index 0000000..024d81d
--- /dev/null
+++ b/src/lib/child-wait.c
@@ -0,0 +1,139 @@
+/* Copyright (c) 2007-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "lib-signals.h"
+#include "hash.h"
+#include "child-wait.h"
+
+#include <sys/wait.h>
+
+struct child_wait {
+	unsigned int pid_count;
+
+	child_wait_callback_t *callback;
+	void *context;
+};
+
+static int child_wait_refcount = 0;
+
+/* pid_t => wait */
+static HASH_TABLE(void *, struct child_wait *) child_pids;
+
+static void
+sigchld_handler(const siginfo_t *si ATTR_UNUSED, void *context ATTR_UNUSED);
+
+#undef child_wait_new_with_pid
+struct child_wait *
+child_wait_new_with_pid(pid_t pid, child_wait_callback_t *callback,
+			void *context)
+{
+	struct child_wait *wait;
+
+	wait = i_new(struct child_wait, 1);
+	wait->callback = callback;
+	wait->context = context;
+
+	if (pid != (pid_t)-1)
+		child_wait_add_pid(wait, pid);
+	return wait;
+}
+
+void child_wait_free(struct child_wait **_wait)
+{
+	struct child_wait *wait = *_wait;
+	struct hash_iterate_context *iter;
+	void *key;
+	struct child_wait *value;
+
+	*_wait = NULL;
+
+	if (wait->pid_count > 0) {
+		/* this should be rare, so iterating hash is fast enough */
+		iter = hash_table_iterate_init(child_pids);
+		while (hash_table_iterate(iter, child_pids, &key, &value)) {
+			if (value == wait) {
+				hash_table_remove(child_pids, key);
+				if (--wait->pid_count == 0)
+					break;
+			}
+		}
+		hash_table_iterate_deinit(&iter);
+	}
+
+	i_free(wait);
+}
+
+void child_wait_add_pid(struct child_wait *wait, pid_t pid)
+{
+	wait->pid_count++;
+	hash_table_insert(child_pids, POINTER_CAST(pid), wait);
+
+	lib_signals_set_expected(SIGCHLD, TRUE, sigchld_handler, NULL);
+}
+
+void child_wait_remove_pid(struct child_wait *wait, pid_t pid)
+{
+	wait->pid_count--;
+	hash_table_remove(child_pids, POINTER_CAST(pid));
+
+	if (hash_table_count(child_pids) == 0)
+		lib_signals_set_expected(SIGCHLD, FALSE, sigchld_handler, NULL);
+}
+
+static void
+sigchld_handler(const siginfo_t *si ATTR_UNUSED, void *context ATTR_UNUSED)
+{
+	struct child_wait_status status;
+
+	while ((status.pid = waitpid(-1, &status.status, WNOHANG)) > 0) {
+		status.wait = hash_table_lookup(child_pids,
+						POINTER_CAST(status.pid));
+		if (status.wait != NULL) {
+			child_wait_remove_pid(status.wait, status.pid);
+			status.wait->callback(&status, status.wait->context);
+		}
+	}
+
+	if (status.pid == -1 && errno != EINTR && errno != ECHILD)
+		i_error("waitpid() failed: %m");
+}
+
+void child_wait_switch_ioloop(void)
+{
+	lib_signals_switch_ioloop(SIGCHLD, sigchld_handler, NULL);
+}
+
+void child_wait_init(void)
+{
+	if (child_wait_refcount++ > 0) {
+		child_wait_switch_ioloop();
+		return;
+	}
+
+	hash_table_create_direct(&child_pids, default_pool, 0);
+
+	lib_signals_set_handler(SIGCHLD, LIBSIG_FLAGS_SAFE,
+		sigchld_handler, NULL);
+}
+
+void child_wait_deinit(void)
+{
+	struct hash_iterate_context *iter;
+	void *key;
+	struct child_wait *value;
+
+	i_assert(child_wait_refcount > 0);
+	if (--child_wait_refcount > 0) {
+		child_wait_switch_ioloop();
+		return;
+	}
+
+	lib_signals_unset_handler(SIGCHLD, sigchld_handler, NULL);
+
+	iter = hash_table_iterate_init(child_pids);
+	while (hash_table_iterate(iter, child_pids, &key, &value))
+		i_free(value);
+	hash_table_iterate_deinit(&iter);
+
+	hash_table_destroy(&child_pids);
+}