diff --git a/src/core/iomgr/fd_posix.c b/src/core/iomgr/fd_posix.c
index 33d90872c30319416f4c1783b9ed074a2a6e1a4e..5bbf171c6d4f0cc776b9dee34fa0ab6dc907162b 100644
--- a/src/core/iomgr/fd_posix.c
+++ b/src/core/iomgr/fd_posix.c
@@ -302,7 +302,8 @@ void grpc_fd_shutdown(grpc_fd *fd) {
   set_ready_locked(&fd->writest, &fd->shutdown_closures[0], &ncb);
   gpr_mu_unlock(&fd->set_state_mu);
   GPR_ASSERT(ncb <= 2);
-  process_callbacks(fd->shutdown_closures[0], ncb, 0, 0);
+  process_callbacks(fd->shutdown_closures[0], ncb, 0 /* GPR_FALSE */,
+                    0 /* GPR_FALSE */);
 }
 
 void grpc_fd_notify_on_read(grpc_fd *fd, grpc_iomgr_closure *closure) {
diff --git a/src/core/iomgr/iomgr.c b/src/core/iomgr/iomgr.c
index 85867b6edfe20d68441eedeab1dba578b4db2fb2..b983a89daa87d33dc500548c051644a11448cf8d 100644
--- a/src/core/iomgr/iomgr.c
+++ b/src/core/iomgr/iomgr.c
@@ -163,7 +163,6 @@ void grpc_iomgr_closure_init(grpc_iomgr_closure *closure, grpc_iomgr_cb_func cb,
                              void *cb_arg) {
   closure->cb = cb;
   closure->cb_arg = cb_arg;
-  closure->success = -1;  /* uninitialized */
   closure->next = NULL;
 }
 
@@ -182,7 +181,7 @@ void grpc_iomgr_add_delayed_callback(grpc_iomgr_closure *closure, int success) {
 
 
 void grpc_iomgr_add_callback(grpc_iomgr_closure *closure) {
-  grpc_iomgr_add_delayed_callback(closure, 1);
+  grpc_iomgr_add_delayed_callback(closure, 1 /* GPR_TRUE */);
 }
 
 
diff --git a/src/core/iomgr/iomgr.h b/src/core/iomgr/iomgr.h
index 913f83f80e7502536ad40b817716f7b015e5b56c..a10e481e481d238bfa0103f878773d3140a8d7c2 100644
--- a/src/core/iomgr/iomgr.h
+++ b/src/core/iomgr/iomgr.h
@@ -34,29 +34,43 @@
 #ifndef GRPC_INTERNAL_CORE_IOMGR_IOMGR_H
 #define GRPC_INTERNAL_CORE_IOMGR_IOMGR_H
 
-/* gRPC Callback definition */
+/** gRPC Callback definition.
+ *
+ * \param arg Arbitrary input.
+ * \param success An indication on the state of the iomgr. On false, cleanup
+ * actions should be taken (eg, shutdown). */
 typedef void (*grpc_iomgr_cb_func)(void *arg, int success);
 
+/** A closure over a grpc_iomgr_cb_func. */
 typedef struct grpc_iomgr_closure {
+  /** Bound callback. */
   grpc_iomgr_cb_func cb;
+
+  /** Arguments to be passed to "cb". */
   void *cb_arg;
+
+  /** Internal. A boolean indication to "cb" on the state of the iomgr.
+   * For instance, closures created during a shutdown would have this field set
+   * to false. */
   int success;
-  struct grpc_iomgr_closure *next;  /** Do not touch */
+
+  /**< Internal. Do not touch */
+  struct grpc_iomgr_closure *next;
 } grpc_iomgr_closure;
 
+/** Initializes \a closure with \a cb and \a cb_arg. */
 void grpc_iomgr_closure_init(grpc_iomgr_closure *closure, grpc_iomgr_cb_func cb,
                              void *cb_arg);
 
-/* TODO(dgq): get rid of the managed_closure concept. */
-void grpc_iomgr_managed_closure_init(grpc_iomgr_closure *manager,
-                                     grpc_iomgr_cb_func managed_cb,
-                                     void *managed_cb_arg);
-
+/** Initializes the iomgr. */
 void grpc_iomgr_init(void);
+
+/** Signals the intention to shutdown the iomgr. */
 void grpc_iomgr_shutdown(void);
 
-/* This function is called from within a callback or from anywhere else
-   and causes the invocation of a callback at some point in the future */
+/** Registers a closure to be invoked at some point in the future.
+ *
+ * Can be called from within a callback or from anywhere else */
 void grpc_iomgr_add_callback(grpc_iomgr_closure *closure);
 
 #endif  /* GRPC_INTERNAL_CORE_IOMGR_IOMGR_H */
diff --git a/src/core/iomgr/pollset_windows.c b/src/core/iomgr/pollset_windows.c
index 5af0685f9d97818dee8255028af3db176155174f..b1f4c09a2cf07217b18df61f4fb11a45be854e6e 100644
--- a/src/core/iomgr/pollset_windows.c
+++ b/src/core/iomgr/pollset_windows.c
@@ -66,15 +66,15 @@ int grpc_pollset_work(grpc_pollset *pollset, gpr_timespec deadline) {
   gpr_timespec now;
   now = gpr_now();
   if (gpr_time_cmp(now, deadline) > 0) {
-    return 0;
+    return 0 /* GPR_FALSE */;
   }
-  if (grpc_maybe_call_delayed_callbacks(NULL, 1)) {
-    return 1;
+  if (grpc_maybe_call_delayed_callbacks(NULL, 1 /* GPR_TRUE */)) {
+    return 1 /* GPR_TRUE */;
   }
   if (grpc_alarm_check(NULL, now, &deadline)) {
-    return 1;
+    return 1 /* GPR_TRUE */;
   }
-  return 0;
+  return 0 /* GPR_FALSE */;
 }
 
 void grpc_pollset_kick(grpc_pollset *p) { }