1 files changed, 116 insertions, 0 deletions
diff --git a/src/core/lib/iomgr/is_epollexclusive_available.c b/src/core/lib/iomgr/is_epollexclusive_available.c
new file mode 100644
index 0000000000..34fcf313e5
--- /dev/null
+++ b/src/core/lib/iomgr/is_epollexclusive_available.c
@@ -0,0 +1,116 @@
+/*
+ *
+ * Copyright 2017, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#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 */
+      .events = (uint32_t)(EPOLLET | EPOLLIN | EPOLLEXCLUSIVE | EPOLLONESHOT),
+      .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