SERVER-28421 Implement ClockSource::waitForConditionUntil()

1 files changed, 87 insertions, 0 deletions

diff --git a/src/mongo/util/clock_source.cpp b/src/mongo/util/clock_source.cpp
new file mode 100644
index 00000000000..c8e70537dbc
--- /dev/null
+++ b/src/mongo/util/clock_source.cpp
@@ -0,0 +1,87 @@
+/**
+ *    Copyright (C) 2017 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/stdx/thread.h"
+#include "mongo/util/clock_source.h"
+
+namespace mongo {
+stdx::cv_status ClockSource::waitForConditionUntil(stdx::condition_variable& cv,
+                                                   stdx::unique_lock<stdx::mutex>& m,
+                                                   Date_t deadline) {
+    if (_tracksSystemClock) {
+        return cv.wait_until(m, deadline.toSystemTimePoint());
+    }
+
+    // The rest of this function only runs during testing, when the clock source is virtualized and
+    // does not track the system clock.
+
+    if (deadline <= now()) {
+        return stdx::cv_status::timeout;
+    }
+
+    struct AlarmInfo {
+        stdx::mutex controlMutex;
+        stdx::mutex* waitMutex;
+        stdx::condition_variable* waitCV;
+        stdx::cv_status cvWaitResult = stdx::cv_status::no_timeout;
+    };
+    auto alarmInfo = std::make_shared<AlarmInfo>();
+    alarmInfo->waitCV = &cv;
+    alarmInfo->waitMutex = m.mutex();
+    const auto waiterThreadId = stdx::this_thread::get_id();
+    bool invokedAlarmInline = false;
+    invariantOK(setAlarm(deadline, [alarmInfo, waiterThreadId, &invokedAlarmInline] {
+        stdx::lock_guard<stdx::mutex> controlLk(alarmInfo->controlMutex);
+        alarmInfo->cvWaitResult = stdx::cv_status::timeout;
+        if (!alarmInfo->waitMutex) {
+            return;
+        }
+        if (stdx::this_thread::get_id() == waiterThreadId) {
+            // In NetworkInterfaceMock, setAlarm may invoke its callback immediately if the deadline
+            // has expired, so we detect that case and avoid self-deadlock by returning early, here.
+            // It is safe to set invokedAlarmInline without synchronization in this case, because it
+            // is exactly the case where the same thread is writing and consulting the value.
+            invokedAlarmInline = true;
+            return;
+        }
+        stdx::lock_guard<stdx::mutex> waitLk(*alarmInfo->waitMutex);
+        alarmInfo->waitCV->notify_all();
+    }));
+    if (!invokedAlarmInline) {
+        cv.wait(m);
+    }
+    m.unlock();
+    stdx::lock_guard<stdx::mutex> controlLk(alarmInfo->controlMutex);
+    m.lock();
+    alarmInfo->waitMutex = nullptr;
+    alarmInfo->waitCV = nullptr;
+    return alarmInfo->cvWaitResult;
+}
+}  // namespace mongo