SERVER-13792 added runtime and build-time checks for POSIX monotonic clocks. de-inlined Timer::now() implementations

6 files changed, 68 insertions, 236 deletions

diff --git a/src/mongo/util/timer-generic-inl.h b/src/mongo/util/timer-generic-inl.h
deleted file mode 100644
index c0b07c563d7..00000000000
--- a/src/mongo/util/timer-generic-inl.h
+++ /dev/null
@@ -1,49 +0,0 @@
-// @file mongo/util/timer-generic-inl.h
-
-/*    Copyright 2010 10gen 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.
- */
-
-/**
- * Inline function implementations for the "generic" implementation of the
- * Timer class.  This implementation often has pretty poor resolution, but is available
- * on all supported platforms.
- *
- * This file should only be included through timer-inl.h, which selects the
- * particular implementation based on target platform.
- */
-
-#pragma once
-
-#define MONGO_TIMER_IMPL_GENERIC
-
-#include "mongo/util/time_support.h"
-
-namespace mongo {
-
-    long long Timer::now() const { return curTimeMicros64(); }
-
-}  // namespace mongo
diff --git a/src/mongo/util/timer-inl.h b/src/mongo/util/timer-inl.h
deleted file mode 100644
index d4e037e2e96..00000000000
--- a/src/mongo/util/timer-inl.h
+++ /dev/null
@@ -1,60 +0,0 @@
-// @file mongo/util/timer-inl.h
-
-/*    Copyright 2010 10gen 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.
- */
-
-/**
- * Inline function implementations for the Timer class.  This file simply selects
- * the platform-appropriate inline functions to include.
- *
- * This file should only be included through timer-inl.h, which selects the
- * particular implementation based on target platform.
- */
-
-#pragma once
-
-#if defined(MONGO_HAVE_HEADER_UNISTD_H)
-#include <unistd.h>
-#endif
-
-#if defined(_WIN32)
-
-// On Windows, prefer the Windows-specific implementation, which employs QueryPerformanceCounter.
-#include "mongo/util/timer-win32-inl.h"
-
-#elif defined(_POSIX_TIMERS) and _POSIX_TIMERS > 0 and defined(_POSIX_MONOTONIC_CLOCK) and _POSIX_MONOTONIC_CLOCK > 0
-
-// On systems that support the POSIX clock_gettime function, and the "monotonic" clock,
-// use those.
-#include "mongo/util/timer-posixclock-inl.h"
-
-#else
-
-// If all else fails, fall back to a generic implementation.  Performance may suffer.
-#include "mongo/util/timer-generic-inl.h"
-
-#endif
diff --git a/src/mongo/util/timer-posixclock-inl.h b/src/mongo/util/timer-posixclock-inl.h
deleted file mode 100644
index a171c25ab0d..00000000000
--- a/src/mongo/util/timer-posixclock-inl.h
+++ /dev/null
@@ -1,58 +0,0 @@
-/*    Copyright 2010 10gen 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.
- */
-
-/**
- * Inline function implementations for timers on systems that support the
- * POSIX clock API and CLOCK_MONOTONIC clock.
- *
- * This file should only be included through timer-inl.h, which selects the
- * particular implementation based on target platform.
- */
-
-#define MONGO_TIMER_IMPL_POSIX_MONOTONIC_CLOCK
-
-#include <ctime>
-
-#include "mongo/util/assert_util.h"
-
-namespace mongo {
-
-    long long Timer::now() const {
-        timespec the_time;
-        long long result;
-
-        fassert(16160, !clock_gettime(CLOCK_MONOTONIC, &the_time));
-
-        // Safe for 292 years after the clock epoch, even if we switch to a signed time value.  On
-        // Linux, the monotonic clock's epoch is the UNIX epoch.
-        result = static_cast<long long>(the_time.tv_sec);
-        result *= nanosPerSecond;
-        result += static_cast<long long>(the_time.tv_nsec);
-        return result;
-    }
-
-}  // namespace mongo
diff --git a/src/mongo/util/timer-win32-inl.h b/src/mongo/util/timer-win32-inl.h
deleted file mode 100644
index dedf77ca385..00000000000
--- a/src/mongo/util/timer-win32-inl.h
+++ /dev/null
@@ -1,54 +0,0 @@
-// @file mongo/util/timer-win32-inl.h
-
-/*    Copyright 2010 10gen 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.
- */
-
-/**
- * Inline function implementations for the Windows-specific implementation of the
- * Timer class.  Windows selects the best available timer, in its estimation, for
- * measuring time at high resolution.  This may be the HPET of the TSC on x86 systems,
- * but is promised to be synchronized across processors, barring BIOS errors.
- *
- * Do not include directly.  Include "mongo/util/timer.h".
- */
-
-#pragma once
-
-#define MONGO_TIMER_IMPL_WIN32
-
-#include "mongo/platform/windows_basic.h"
-#include "mongo/util/assert_util.h"
-
-namespace mongo {
-
-    long long Timer::now() const {
-        LARGE_INTEGER i;
-        fassert(16161, QueryPerformanceCounter(&i));
-        return i.QuadPart;
-    }
-
-}  // namespace mongo
diff --git a/src/mongo/util/timer.cpp b/src/mongo/util/timer.cpp
index 597c4e15aa5..90e61b55423 100644
--- a/src/mongo/util/timer.cpp
+++ b/src/mongo/util/timer.cpp
@@ -27,14 +27,25 @@
  *    then also delete it in the license file.
  */
 
+#include "mongo/platform/basic.h"
+
 #include "mongo/util/timer.h"
 
+#include <ctime>
 #include <limits>
+#if defined(MONGO_HAVE_HEADER_UNISTD_H)
+#include <unistd.h>
+#endif
+
+#include "mongo/util/assert_util.h"
+#include "mongo/util/time_support.h"
 
 namespace mongo {
 
-    // default value of 1 so that during startup initialization if referenced no division by zero
-    long long Timer::_countsPerSecond = 1;
+    // Set default value to reflect "generic" timer implementation.
+    // Define Timer::_countsPerSecond before static initializer "atstartuputil" to ensure correct
+    // relative sequencing regardless of how _countsPerSecond is initialized (static or dynamic).
+    long long Timer::_countsPerSecond = Timer::microsPerSecond;
 
     namespace {
 
@@ -43,19 +54,66 @@ namespace mongo {
             AtStartup();
         } atstartuputil;
 
-#if defined(MONGO_TIMER_IMPL_WIN32)
+        // "Generic" implementation for Timer::now().
+        long long _timerNowGeneric() {
+            return curTimeMicros64();
+        }
+
+        // Function pointer to Timer::now() implementation.
+        // Overridden in AtStartup() with better implementation where available.
+        long long (*_timerNow)() = &_timerNowGeneric;
+
+#if defined(_WIN32)
+
+        /**
+         * Windows-specific implementation of the
+         * Timer class.  Windows selects the best available timer, in its estimation, for
+         * measuring time at high resolution.  This may be the HPET of the TSC on x86 systems,
+         * but is promised to be synchronized across processors, barring BIOS errors.
+         */
+        long long timerNowWindows() {
+            LARGE_INTEGER i;
+            fassert(16161, QueryPerformanceCounter(&i));
+            return i.QuadPart;
+        }
 
         AtStartup::AtStartup() {
             LARGE_INTEGER x;
             bool ok = QueryPerformanceFrequency(&x);
             verify(ok);
             Timer::_countsPerSecond = x.QuadPart;
+            _timerNow = &timerNowWindows;
         }
 
-#elif defined(MONGO_TIMER_IMPL_POSIX_MONOTONIC_CLOCK)
+#elif defined(MONGO_HAVE_POSIX_MONOTONIC_CLOCK)
+
+        /**
+         * Implementation for timer on systems that support the
+         * POSIX clock API and CLOCK_MONOTONIC clock.
+         */
+        long long timerNowPosixMonotonicClock() {
+            timespec the_time;
+            long long result;
+
+            fassert(16160, !clock_gettime(CLOCK_MONOTONIC, &the_time));
+
+            // Safe for 292 years after the clock epoch, even if we switch to a signed time value.
+            // On Linux, the monotonic clock's epoch is the UNIX epoch.
+            result = static_cast<long long>(the_time.tv_sec);
+            result *= Timer::nanosPerSecond;
+            result += static_cast<long long>(the_time.tv_nsec);
+            return result;
+        }
 
         AtStartup::AtStartup() {
+            // If the monotonic clock is not available at runtime (sysconf() returns 0 or -1),
+            // do not override the generic implementation or modify Timer::_countsPerSecond.
+            if (sysconf(_SC_MONOTONIC_CLOCK) <= 0) {
+                return;
+            }
+
             Timer::_countsPerSecond = Timer::nanosPerSecond;
+            _timerNow = &timerNowPosixMonotonicClock;
 
             // Make sure that the current time relative to the (unspecified) epoch isn't already too
             // big to represent as a 64-bit count of nanoseconds.
@@ -65,17 +123,14 @@ namespace mongo {
             fassert(16162, !clock_gettime(CLOCK_MONOTONIC, &the_time));
             fassert(16163, static_cast<long long>(the_time.tv_sec) < maxSecs);
         }
-
-#elif defined(MONGO_TIMER_IMPL_GENERIC)
-
-        AtStartup::AtStartup() {
-            Timer::_countsPerSecond = Timer::microsPerSecond;
-        }
-
 #else
-#error "Unknown mongo::Timer implementation"
+        AtStartup::AtStartup() { }
 #endif
 
     }  // namespace
 
+    long long Timer::now() const {
+        return _timerNow();
+    }
+
 }  // namespace mongo
diff --git a/src/mongo/util/timer.h b/src/mongo/util/timer.h
index 0d5a5e97ebc..b28db52d703 100644
--- a/src/mongo/util/timer.h
+++ b/src/mongo/util/timer.h
@@ -85,10 +85,8 @@ namespace mongo {
         static long long _countsPerSecond;
 
     private:
-        inline long long now() const;
+        long long now() const;
 
         long long _old;
     };
 }  // namespace mongo
-
-#include "mongo/util/timer-inl.h"