Handle pollsets and fds witn no polling islands and fix locking bug in pollset_add_fd

src/core/lib/iomgr/ev_epoll_linux.c

@@ -701,12 +701,14 @@ static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
      - Decrement the ref count on the polling island and det fd->polling_island
        to NULL */
   gpr_mu_lock(&fd->pi_mu);
-
-  fd->polling_island = polling_island_update_and_lock(fd->polling_island, 1, 0);
-  polling_island_remove_fd_locked(fd->polling_island, fd, !fd->released, true);
+  if (fd->polling_island != NULL) {
+    fd->polling_island =
+        polling_island_update_and_lock(fd->polling_island, 1, 0);
+    polling_island_remove_fd_locked(fd->polling_island, fd, !fd->released,
+                                    true);
     polling_island_unref_and_unlock(fd->polling_island, 1);
     fd->polling_island = NULL;
-
+  }
   gpr_mu_unlock(&fd->pi_mu);
 
   grpc_exec_ctx_enqueue(exec_ctx, fd->on_done_closure, true, NULL);
@@ -926,13 +928,12 @@ static void fd_become_writable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
   set_ready(exec_ctx, fd, &fd->write_closure);
 }
 
-/* TODO(klempner): We probably want to turn this down a bit */
 #define GRPC_EPOLL_MAX_EVENTS 1000
 static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
                                     grpc_pollset *pollset, int timeout_ms,
                                     sigset_t *sig_mask) {
   struct epoll_event ep_ev[GRPC_EPOLL_MAX_EVENTS];
-  int epoll_fd;
+  int epoll_fd = -1;
   int ep_rv;
   GPR_TIMER_BEGIN("pollset_work_and_unlock", 0);
 
@@ -943,16 +944,19 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
      - pollset->pi_mu
      - pollset->polling_island->mu */
   gpr_mu_lock(&pollset->pi_mu);
+
+  if (pollset->polling_island != NULL) {
     pollset->polling_island =
         polling_island_update_and_lock(pollset->polling_island, 1, 0);
-
     epoll_fd = pollset->polling_island->epoll_fd;
+    gpr_mu_unlock(&pollset->polling_island->mu);
+  }
 
-  /* Release the locks */
-  polling_island_unref_and_unlock(pollset->polling_island, 0); /* Keep the ref*/
   gpr_mu_unlock(&pollset->pi_mu);
   gpr_mu_unlock(&pollset->mu);
 
+  /* If epoll_fd == -1, this is a blank pollset and does not have any fds yet */
+  if (epoll_fd != -1) {
     do {
       ep_rv = epoll_pwait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, timeout_ms,
                           sig_mask);
@@ -982,6 +986,7 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
         }
       }
     } while (ep_rv == GRPC_EPOLL_MAX_EVENTS);
+  }
 
   GPR_TIMER_END("pollset_work_and_unlock", 0);
 }
@@ -1141,8 +1146,10 @@ static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
     }
   } else if (fd->polling_island == NULL) {
     pi_new = polling_island_update_and_lock(pollset->polling_island, 1, 1);
+    gpr_mu_unlock(&pi_new->mu);
   } else if (pollset->polling_island == NULL) {
     pi_new = polling_island_update_and_lock(fd->polling_island, 1, 1);
+    gpr_mu_unlock(&pi_new->mu);
   } else {
     pi_new = polling_island_merge(fd->polling_island, pollset->polling_island);
   }