Merge branch 'master' of github.com:grpc/grpc into grpclb_pick_from_shutdown_rr

1 files changed, 101 insertions, 0 deletions

diff --git a/src/core/lib/iomgr/is_epollexclusive_available.cc b/src/core/lib/iomgr/is_epollexclusive_available.cc
new file mode 100644
index 0000000000..d08844c0df
--- /dev/null
+++ b/src/core/lib/iomgr/is_epollexclusive_available.cc
@@ -0,0 +1,101 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/iomgr/port.h"
+
+#include "src/core/lib/iomgr/is_epollexclusive_available.h"
+
+#ifdef GRPC_LINUX_EPOLL
+
+#include <grpc/support/log.h>
+
+#include <errno.h>
+#include <sys/eventfd.h>
+#include <unistd.h>
+
+#include "src/core/lib/iomgr/sys_epoll_wrapper.h"
+
+/* This polling engine is only relevant on linux kernels supporting epoll() */
+bool grpc_is_epollexclusive_available(void) {
+  static bool logged_why_not = false;
+
+  int fd = epoll_create1(EPOLL_CLOEXEC);
+  if (fd < 0) {
+    if (!logged_why_not) {
+      gpr_log(GPR_ERROR,
+              "epoll_create1 failed with error: %d. Not using epollex polling "
+              "engine.",
+              fd);
+      logged_why_not = true;
+    }
+    return false;
+  }
+  int evfd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
+  if (evfd < 0) {
+    if (!logged_why_not) {
+      gpr_log(GPR_ERROR,
+              "eventfd failed with error: %d. Not using epollex polling "
+              "engine.",
+              fd);
+      logged_why_not = true;
+    }
+    close(fd);
+    return false;
+  }
+  struct epoll_event ev;
+  /* choose events that should cause an error on
+     EPOLLEXCLUSIVE enabled kernels - specifically the combination of
+     EPOLLONESHOT and EPOLLEXCLUSIVE */
+  ev.events = (uint32_t)(EPOLLET | EPOLLIN | EPOLLEXCLUSIVE | EPOLLONESHOT);
+  ev.data.ptr = NULL;
+  if (epoll_ctl(fd, EPOLL_CTL_ADD, evfd, &ev) != 0) {
+    if (errno != EINVAL) {
+      if (!logged_why_not) {
+        gpr_log(
+            GPR_ERROR,
+            "epoll_ctl with EPOLLEXCLUSIVE | EPOLLONESHOT failed with error: "
+            "%d. Not using epollex polling engine.",
+            errno);
+        logged_why_not = true;
+      }
+      close(fd);
+      close(evfd);
+      return false;
+    }
+  } else {
+    if (!logged_why_not) {
+      gpr_log(GPR_ERROR,
+              "epoll_ctl with EPOLLEXCLUSIVE | EPOLLONESHOT succeeded. This is "
+              "evidence of no EPOLLEXCLUSIVE support. Not using "
+              "epollex polling engine.");
+      logged_why_not = true;
+    }
+    close(fd);
+    close(evfd);
+    return false;
+  }
+  close(evfd);
+  close(fd);
+  return true;
+}
+
+#else
+
+bool grpc_is_epollexclusive_available(void) { return false; }
+
+#endif