Drain readable fd

1 files changed, 43 insertions, 4 deletions

diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_posix.c b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_posix.c
index 7f1f57259a..d38fe66d06 100644
--- a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_posix.c
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_posix.c
@@ -20,6 +20,7 @@
 #if GRPC_ARES == 1 && defined(GRPC_POSIX_SOCKET)
 
 #include <ares.h>
+#include <sys/ioctl.h>
 
 #include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h"
 
@@ -54,6 +55,8 @@ typedef struct fd_node {
   bool readable_registered;
   /** if the writable closure has been registered */
   bool writable_registered;
+  /** if the fd is being shut down */
+  bool shutting_down;
 } fd_node;
 
 struct grpc_ares_ev_driver {
@@ -100,7 +103,6 @@ static void fd_node_destroy(grpc_exec_ctx *exec_ctx, fd_node *fdn) {
   GPR_ASSERT(!fdn->readable_registered);
   GPR_ASSERT(!fdn->writable_registered);
   gpr_mu_destroy(&fdn->mu);
-  grpc_pollset_set_del_fd(exec_ctx, fdn->ev_driver->pollset_set, fdn->fd);
   /* c-ares library has closed the fd inside grpc_fd. This fd may be picked up
      immediately by another thread, and should not be closed by the following
      grpc_fd_orphan. */
@@ -109,6 +111,20 @@ static void fd_node_destroy(grpc_exec_ctx *exec_ctx, fd_node *fdn) {
   gpr_free(fdn);
 }
 
+static void fd_node_shutdown(grpc_exec_ctx *exec_ctx, fd_node *fdn) {
+  gpr_mu_lock(&fdn->mu);
+  fdn->shutting_down = true;
+  if (!fdn->readable_registered && !fdn->writable_registered) {
+    gpr_mu_unlock(&fdn->mu);
+    fd_node_destroy(exec_ctx, fdn);
+  } else {
+    grpc_fd_shutdown(
+        exec_ctx, fdn->fd,
+        GRPC_ERROR_CREATE_FROM_STATIC_STRING("c-ares fd shutdown"));
+    gpr_mu_unlock(&fdn->mu);
+  }
+}
+
 grpc_error *grpc_ares_ev_driver_create(grpc_ares_ev_driver **ev_driver,
                                        grpc_pollset_set *pollset_set) {
   *ev_driver = (grpc_ares_ev_driver *)gpr_malloc(sizeof(grpc_ares_ev_driver));
@@ -175,18 +191,34 @@ static fd_node *pop_fd_node(fd_node **head, int fd) {
   return NULL;
 }
 
+/* Check if \a fd is still readable */
+static bool grpc_ares_is_fd_still_readable(grpc_ares_ev_driver *ev_driver,
+                                           int fd) {
+  size_t bytes_available = 0;
+  return ioctl(fd, FIONREAD, &bytes_available) == 0 && bytes_available > 0;
+}
+
 static void on_readable_cb(grpc_exec_ctx *exec_ctx, void *arg,
                            grpc_error *error) {
   fd_node *fdn = (fd_node *)arg;
   grpc_ares_ev_driver *ev_driver = fdn->ev_driver;
   gpr_mu_lock(&fdn->mu);
   fdn->readable_registered = false;
+  if (fdn->shutting_down && !fdn->writable_registered) {
+    gpr_mu_unlock(&fdn->mu);
+    fd_node_destroy(exec_ctx, fdn);
+    grpc_ares_ev_driver_unref(ev_driver);
+    return;
+  }
   gpr_mu_unlock(&fdn->mu);
 
   gpr_log(GPR_DEBUG, "readable on %d", grpc_fd_wrapped_fd(fdn->fd));
   if (error == GRPC_ERROR_NONE) {
-    ares_process_fd(ev_driver->channel, grpc_fd_wrapped_fd(fdn->fd),
-                    ARES_SOCKET_BAD);
+    do {
+      ares_process_fd(ev_driver->channel, grpc_fd_wrapped_fd(fdn->fd),
+                      ARES_SOCKET_BAD);
+    } while (
+        grpc_ares_is_fd_still_readable(ev_driver, grpc_fd_wrapped_fd(fdn->fd)));
   } else {
     // If error is not GRPC_ERROR_NONE, it means the fd has been shutdown or
     // timed out. The pending lookups made on this ev_driver will be cancelled
@@ -208,6 +240,12 @@ static void on_writable_cb(grpc_exec_ctx *exec_ctx, void *arg,
   grpc_ares_ev_driver *ev_driver = fdn->ev_driver;
   gpr_mu_lock(&fdn->mu);
   fdn->writable_registered = false;
+  if (fdn->shutting_down && !fdn->readable_registered) {
+    gpr_mu_unlock(&fdn->mu);
+    fd_node_destroy(exec_ctx, fdn);
+    grpc_ares_ev_driver_unref(ev_driver);
+    return;
+  }
   gpr_mu_unlock(&fdn->mu);
 
   gpr_log(GPR_DEBUG, "writable on %d", grpc_fd_wrapped_fd(fdn->fd));
@@ -256,6 +294,7 @@ static void grpc_ares_notify_on_event_locked(grpc_exec_ctx *exec_ctx,
           fdn->ev_driver = ev_driver;
           fdn->readable_registered = false;
           fdn->writable_registered = false;
+          fdn->shutting_down = false;
           gpr_mu_init(&fdn->mu);
           GRPC_CLOSURE_INIT(&fdn->read_closure, on_readable_cb, fdn,
                             grpc_schedule_on_exec_ctx);
@@ -296,7 +335,7 @@ static void grpc_ares_notify_on_event_locked(grpc_exec_ctx *exec_ctx,
   while (ev_driver->fds != NULL) {
     fd_node *cur = ev_driver->fds;
     ev_driver->fds = ev_driver->fds->next;
-    fd_node_destroy(exec_ctx, cur);
+    fd_node_shutdown(exec_ctx, cur);
   }
   ev_driver->fds = new_list;
   // If the ev driver has no working fd, all the tasks are done.