linux: handle EPOLLHUP without EPOLLIN/EPOLLOUT

Work around an epoll quirk where it sometimes reports just the EPOLLERR
or EPOLLHUP event.  In order to force the event loop to move forward,
we merge in the read/write events that the watcher is interested in;
uv__read() and uv__write() will then deal with the error or hangup in
the usual fashion.

Fixes #982.

Makefile.am

@@ -118,6 +118,7 @@ test_run_tests_SOURCES = test/blackhole-server.c \
                          test/test-barrier.c \
                          test/test-callback-order.c \
                          test/test-callback-stack.c \
+                         test/test-close-fd.c \
                          test/test-close-order.c \
                          test/test-condvar.c \
                          test/test-connection-fail.c \

src/unix/linux-core.c

@@ -113,7 +113,6 @@ void uv__io_poll(uv_loop_t* loop, int timeout) {
   uv__io_t* w;
   uint64_t base;
   uint64_t diff;
-  unsigned int masked_events;
   int nevents;
   int count;
   int nfds;
@@ -217,16 +216,35 @@ void uv__io_poll(uv_loop_t* loop, int timeout) {
         continue;
       }
 
-      /*
-       * Give users only events they're interested in. Prevents spurious
+      /* Give users only events they're interested in. Prevents spurious
        * callbacks when previous callback invocation in this loop has stopped
        * the current watcher. Also, filters out events that users has not
        * requested us to watch.
        */
-      masked_events = pe->events & w->pevents;
-      if (masked_events != 0)
-        w->cb(loop, w, masked_events);
-      nevents++;
+      pe->events &= w->pevents | UV__POLLERR | UV__POLLHUP;
+
+      /* Work around an epoll quirk where it sometimes reports just the
+       * EPOLLERR or EPOLLHUP event.  In order to force the event loop to
+       * move forward, we merge in the read/write events that the watcher
+       * is interested in; uv__read() and uv__write() will then deal with
+       * the error or hangup in the usual fashion.
+       *
+       * Note to self: happens when epoll reports EPOLLIN|EPOLLHUP, the user
+       * reads the available data, calls uv_read_stop(), then sometime later
+       * calls uv_read_start() again.  By then, libuv has forgotten about the
+       * hangup and the kernel won't report EPOLLIN again because there's
+       * nothing left to read.  If anything, libuv is to blame here.  The
+       * current hack is just a quick bandaid; to properly fix it, libuv
+       * needs to remember the error/hangup event.  We should get that for
+       * free when we switch over to edge-triggered I/O.
+       */
+      if (pe->events == UV__EPOLLERR || pe->events == UV__EPOLLHUP)
+        pe->events |= w->pevents & (UV__EPOLLIN | UV__EPOLLOUT);
+
+      if (pe->events != 0) {
+        w->cb(loop, w, pe->events);
+        nevents++;
+      }
     }
 
     if (nevents != 0) {

test/test-close-fd.c

@@ -0,0 +1,77 @@
+/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#if !defined(_WIN32)
+
+#include "uv.h"
+#include "task.h"
+#include <fcntl.h>
+#include <unistd.h>
+
+static unsigned int read_cb_called;
+
+static void alloc_cb(uv_handle_t *handle, size_t size, uv_buf_t *buf) {
+  static char slab[1];
+  buf->base = slab;
+  buf->len = sizeof(slab);
+}
+
+static void read_cb(uv_stream_t *handle, ssize_t nread, const uv_buf_t *buf) {
+  switch (++read_cb_called) {
+  case 1:
+    ASSERT(nread == 1);
+    uv_read_stop(handle);
+    break;
+  case 2:
+    ASSERT(nread == UV_EOF);
+    uv_close((uv_handle_t *) handle, NULL);
+    break;
+  default:
+    ASSERT(!"read_cb_called > 2");
+  }
+}
+
+TEST_IMPL(close_fd) {
+  uv_pipe_t pipe_handle;
+  int fd[2];
+
+  ASSERT(0 == pipe(fd));
+  ASSERT(0 == fcntl(fd[0], F_SETFL, O_NONBLOCK));
+  ASSERT(0 == uv_pipe_init(uv_default_loop(), &pipe_handle, 0));
+  ASSERT(0 == uv_pipe_open(&pipe_handle, fd[0]));
+  fd[0] = -1;  /* uv_pipe_open() takes ownership of the file descriptor. */
+  ASSERT(1 == write(fd[1], "", 1));
+  ASSERT(0 == close(fd[1]));
+  fd[1] = -1;
+  ASSERT(0 == uv_read_start((uv_stream_t *) &pipe_handle, alloc_cb, read_cb));
+  ASSERT(0 == uv_run(uv_default_loop(), UV_RUN_DEFAULT));
+  ASSERT(1 == read_cb_called);
+  ASSERT(0 == uv_is_active((const uv_handle_t *) &pipe_handle));
+  ASSERT(0 == uv_read_start((uv_stream_t *) &pipe_handle, alloc_cb, read_cb));
+  ASSERT(0 == uv_run(uv_default_loop(), UV_RUN_DEFAULT));
+  ASSERT(2 == read_cb_called);
+  ASSERT(0 != uv_is_closing((const uv_handle_t *) &pipe_handle));
+
+  MAKE_VALGRIND_HAPPY();
+  return 0;
+}
+
+#endif  /* !defined(_WIN32) */

test/test-list.h

@@ -223,6 +223,7 @@ TEST_DECLARE   (listen_with_simultaneous_accepts)
 TEST_DECLARE   (listen_no_simultaneous_accepts)
 TEST_DECLARE   (fs_stat_root)
 #else
+TEST_DECLARE   (close_fd)
 TEST_DECLARE   (spawn_setuid_setgid)
 TEST_DECLARE   (we_get_signal)
 TEST_DECLARE   (we_get_signals)
@@ -453,6 +454,7 @@ TASK_LIST_START
   TEST_ENTRY  (listen_no_simultaneous_accepts)
   TEST_ENTRY  (fs_stat_root)
 #else
+  TEST_ENTRY  (close_fd)
   TEST_ENTRY  (spawn_setuid_setgid)
   TEST_ENTRY  (we_get_signal)
   TEST_ENTRY  (we_get_signals)

uv.gyp

@@ -302,6 +302,7 @@
         'test/test-async-null-cb.c',
         'test/test-callback-stack.c',
         'test/test-callback-order.c',
+        'test/test-close-fd.c',
         'test/test-close-order.c',
         'test/test-connection-fail.c',
         'test/test-cwd-and-chdir.c',