Bug 852250 - When restarting recompute the process startup timestamp instead of using the timestamp stored it in MOZ_APP_RESTART during the shutdown procedure. r=nfroyd

xpcom/ds/TimeStamp.cpp

@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Implementation of the OS-independent methods of the TimeStamp class
+ */
+
+#include "mozilla/TimeStamp.h"
+#include "prenv.h"
+
+namespace mozilla {
+
+TimeStamp TimeStamp::sFirstTimeStamp;
+TimeStamp TimeStamp::sProcessCreation;
+
+TimeStamp
+TimeStamp::ProcessCreation(bool& aIsInconsistent)
+{
+  aIsInconsistent = false;
+
+  if (sProcessCreation.IsNull()) {
+    char *mozAppRestart = PR_GetEnv("MOZ_APP_RESTART");
+    TimeStamp ts;
+
+    /* When calling PR_SetEnv() with an empty value the existing variable may
+     * be unset or set to the empty string depending on the underlying platform
+     * thus we have to check if the variable is present and not empty. */
+    if (mozAppRestart && (strcmp(mozAppRestart, "") != 0)) {
+      /* Firefox was restarted, use the first time-stamp we've taken as the new
+       * process startup time and unset MOZ_APP_RESTART. */
+      ts = sFirstTimeStamp;
+      PR_SetEnv("MOZ_APP_RESTART=");
+    } else {
+      TimeStamp now = Now();
+      uint64_t uptime = ComputeProcessUptime();
+
+      ts = now - TimeDuration::FromMicroseconds(uptime);
+
+      if ((ts > sFirstTimeStamp) || (uptime == 0)) {
+        /* If the process creation timestamp was inconsistent replace it with
+         * the first one instead and notify that a telemetry error was
+         * detected. */
+        aIsInconsistent = true;
+        ts = sFirstTimeStamp;
+      }
+    }
+
+    sProcessCreation = ts;
+  }
+
+  return sProcessCreation;
+}
+
+void
+TimeStamp::RecordProcessRestart()
+{
+  PR_SetEnv("MOZ_APP_RESTART=1");
+  sProcessCreation = TimeStamp();
+}
+
+} // namespace mozilla

xpcom/ds/TimeStamp.h

@@ -342,6 +342,16 @@ private:
 
   static TimeStamp Now(bool aHighResolution);
 
+  /**
+   * Computes the uptime of the current process in microseconds. The result
+   * is platform-dependent and needs to be checked against existing timestamps
+   * for consistency.
+   *
+   * @returns The number of microseconds since the calling process was started
+   *          or 0 if an error was encountered while computing the uptime
+   */
+  static uint64_t ComputeProcessUptime();
+
   /**
    * When built with PRIntervalTime, a value of 0 means this instance
    * is "null". Otherwise, the low 32 bits represent a PRIntervalTime,

xpcom/ds/TimeStamp_darwin.cpp

@@ -24,7 +24,6 @@
 
 #include "mozilla/TimeStamp.h"
 #include "nsCRT.h"
-#include "prenv.h"
 #include "prprf.h"
 
 // Estimate of the smallest duration of time we can measure.
@@ -83,9 +82,6 @@ ClockResolutionNs()
 
 namespace mozilla {
 
-TimeStamp TimeStamp::sFirstTimeStamp;
-TimeStamp TimeStamp::sProcessCreation;
-
 double
 TimeDuration::ToSeconds() const
 {
@@ -176,8 +172,8 @@ TimeStamp::Now(bool aHighResolution)
 // Computes and returns the process uptime in microseconds.
 // Returns 0 if an error was encountered.
 
-static uint64_t
-ComputeProcessUptime()
+uint64_t
+TimeStamp::ComputeProcessUptime()
 {
   struct timeval tv;
   int rv = gettimeofday(&tv, NULL);
@@ -212,42 +208,4 @@ ComputeProcessUptime()
   return now - startTime;
 }
 
-TimeStamp
-TimeStamp::ProcessCreation(bool& aIsInconsistent)
-{
-  aIsInconsistent = false;
-
-  if (sProcessCreation.IsNull()) {
-    char *mozAppRestart = PR_GetEnv("MOZ_APP_RESTART");
-    TimeStamp ts;
-
-    if (mozAppRestart) {
-      ts = TimeStamp(nsCRT::atoll(mozAppRestart));
-    } else {
-      TimeStamp now = TimeStamp::Now();
-      uint64_t uptime = ComputeProcessUptime();
-
-      ts = now - TimeDuration::FromMicroseconds(uptime);
-
-      if ((ts > sFirstTimeStamp) || (uptime == 0)) {
-        // If the process creation timestamp was inconsistent replace it with the
-        // first one instead and notify that a telemetry error was detected.
-        aIsInconsistent = true;
-        ts = sFirstTimeStamp;
-      }
-    }
-
-    sProcessCreation = ts;
-  }
-
-  return sProcessCreation;
-}
-
-void
-TimeStamp::RecordProcessRestart()
-{
-  PR_SetEnv(PR_smprintf("MOZ_APP_RESTART=%lld", ClockTime()));
-  sProcessCreation = TimeStamp();
-}
-
-}
+} // namespace mozilla

xpcom/ds/TimeStamp_posix.cpp

@@ -48,7 +48,6 @@
 
 #include "mozilla/TimeStamp.h"
 #include "nsCRT.h"
-#include "prenv.h"
 #include "prprf.h"
 #include "prthread.h"
 
@@ -132,9 +131,6 @@ ClockResolutionNs()
 
 namespace mozilla {
 
-TimeStamp TimeStamp::sFirstTimeStamp;
-TimeStamp TimeStamp::sProcessCreation;
-
 double
 TimeDuration::ToSeconds() const
 {
@@ -283,11 +279,11 @@ ComputeProcessUptimeThread(void *aTime)
   *uptime = ((threadJiffies - selfJiffies) * kNsPerSec) / hz;
 }
 
-// Computes and returns the process uptime in ns on Linux & its derivatives.
+// Computes and returns the process uptime in us on Linux & its derivatives.
 // Returns 0 if an error was encountered.
 
-static uint64_t
-ComputeProcessUptime()
+uint64_t
+TimeStamp::ComputeProcessUptime()
 {
   uint64_t uptime = 0;
   PRThread *thread = PR_CreateThread(PR_USER_THREAD,
@@ -300,17 +296,17 @@ ComputeProcessUptime()
 
   PR_JoinThread(thread);
 
-  return uptime;
+  return uptime / kNsPerUs;
 }
 
 #elif defined(__DragonFly__) || defined(__FreeBSD__) \
       || defined(__NetBSD__) || defined(__OpenBSD__)
 
-// Computes and returns the process uptime in ns on various BSD flavors.
+// Computes and returns the process uptime in us on various BSD flavors.
 // Returns 0 if an error was encountered.
 
-static uint64_t
-ComputeProcessUptime()
+uint64_t
+TimeStamp::ComputeProcessUptime()
 {
   struct timespec ts;
   int rv = clock_gettime(CLOCK_REALTIME, &ts);
@@ -345,55 +341,17 @@ ComputeProcessUptime()
   if (startTime > now)
     return 0;
 
-  return (now - startTime);
+  return (now - startTime) / kNsPerUs;
 }
 
 #else
 
-static uint64_t
-ComputeProcessUptime()
+uint64_t
+TimeStamp::ComputeProcessUptime()
 {
   return 0;
 }
 
 #endif
 
-TimeStamp
-TimeStamp::ProcessCreation(bool& aIsInconsistent)
-{
-  aIsInconsistent = false;
-
-  if (sProcessCreation.IsNull()) {
-    char *mozAppRestart = PR_GetEnv("MOZ_APP_RESTART");
-    TimeStamp ts;
-
-    if (mozAppRestart) {
-      ts = TimeStamp(nsCRT::atoll(mozAppRestart));
-    } else {
-      TimeStamp now = TimeStamp::Now();
-      uint64_t uptime = ComputeProcessUptime();
-
-      ts = now - TimeDuration::FromMicroseconds(uptime / 1000);
-
-      if ((ts > sFirstTimeStamp) || (uptime == 0)) {
-        // If the process creation timestamp was inconsistent replace it with the
-        // first one instead and notify that a telemetry error was detected.
-        aIsInconsistent = true;
-        ts = sFirstTimeStamp;
-      }
-    }
-
-    sProcessCreation = ts;
-  }
-
-  return sProcessCreation;
-}
-
-void
-TimeStamp::RecordProcessRestart()
-{
-  PR_SetEnv(PR_smprintf("MOZ_APP_RESTART=%lld", ClockTimeNs()));
-  sProcessCreation = TimeStamp();
-}
-
-}
+} // namespace mozilla

xpcom/ds/TimeStamp_windows.cpp

@@ -18,7 +18,6 @@
 
 #include "nsCRT.h"
 #include "prlog.h"
-#include "prenv.h"
 #include "prprf.h"
 #include <stdio.h>
 
@@ -183,9 +182,6 @@ static DWORD sLastGTCRollover = 0;
 
 namespace mozilla {
 
-TimeStamp TimeStamp::sFirstTimeStamp;
-TimeStamp TimeStamp::sProcessCreation;
-
 typedef ULONGLONG (WINAPI* GetTickCount64_t)();
 static GetTickCount64_t sGetTickCount64 = nullptr;
 
@@ -562,11 +558,11 @@ TimeStamp::Now(bool aHighResolution)
   return TimeStamp(TimeStampValue(GTC, QPC, useQPC));
 }
 
-// Computes and returns the current process uptime in microseconds.
-// Returns 0 if an error was encountered while computing the uptime.
+// Computes and returns the process uptime in microseconds.
+// Returns 0 if an error was encountered.
 
-static uint64_t
-ComputeProcessUptime()
+uint64_t
+TimeStamp::ComputeProcessUptime()
 {
   SYSTEMTIME nowSys;
   GetSystemTime(&nowSys);
@@ -595,41 +591,4 @@ ComputeProcessUptime()
   return (nowUsec.QuadPart - startUsec.QuadPart) / 10ULL;
 }
 
-TimeStamp
-TimeStamp::ProcessCreation(bool& aIsInconsistent)
-{
-  aIsInconsistent = false;
-
-  if (sProcessCreation.IsNull()) {
-    char *mozAppRestart = PR_GetEnv("MOZ_APP_RESTART");
-    TimeStamp ts;
-
-    if (mozAppRestart) {
-      ts = TimeStamp(TimeStampValue(nsCRT::atoll(mozAppRestart), 0, false));
-    } else {
-      TimeStamp now = TimeStamp::Now();
-      uint64_t uptime = ComputeProcessUptime();
-      ts = now - TimeDuration::FromMicroseconds(static_cast<double>(uptime));
-
-      if ((ts > sFirstTimeStamp) || (uptime == 0)) {
-        // If the process creation timestamp was inconsistent replace it with the
-        // first one instead and notify that a telemetry error was detected.
-        aIsInconsistent = true;
-        ts = sFirstTimeStamp;
-      }
-    }
-
-    sProcessCreation = ts;
-  }
-
-  return sProcessCreation;
-}
-
-void
-TimeStamp::RecordProcessRestart()
-{
-  PR_SetEnv(PR_smprintf("MOZ_APP_RESTART=%lld", ms2mt(sGetTickCount64())));
-  sProcessCreation = TimeStamp();
-}
-
 } // namespace mozilla

xpcom/ds/moz.build

@@ -95,6 +95,7 @@ CPP_SOURCES += [
     'nsSupportsPrimitives.cpp',
     'nsUnicharBuffer.cpp',
     'nsVariant.cpp',
+    'TimeStamp.cpp',
 ]
 
 if CONFIG['OS_ARCH'] == 'WINNT':