From 95cb81c286258e4534afc8426bba53cbdddfd787 Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Sun, 10 Mar 2019 16:34:51 -0700
Subject: [PATCH] generalTime short circuit current time

epicsTimeGetCurrent() is called frequently.
Unless more than the default provider is registered,
locking and going through the timeProvider list each
time is a waste.

Instead, short circuit to directly call the default
time current time provider unless a another has
been registered.
---
 modules/libcom/src/osi/epicsGeneralTime.c    | 16 ++++++++++++++++
 modules/libcom/src/osi/os/Darwin/osdTime.cpp |  2 +-
 modules/libcom/src/osi/os/WIN32/osdTime.cpp  |  5 +++--
 modules/libcom/src/osi/os/posix/osdTime.cpp  |  2 +-
 modules/libcom/src/osi/osiClockTime.c        |  8 ++++----
 5 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/modules/libcom/src/osi/epicsGeneralTime.c b/modules/libcom/src/osi/epicsGeneralTime.c
index d08e9c6a9..dff495ef0 100644
--- a/modules/libcom/src/osi/epicsGeneralTime.c
+++ b/modules/libcom/src/osi/epicsGeneralTime.c
@@ -78,6 +78,11 @@ static epicsThreadOnceId onceId = EPICS_THREAD_ONCE_INIT;
 
 static const char * const tsfmt = "%Y-%m-%d %H:%M:%S.%09f";
 
+/* defined in osiClockTime.c or osdTime.cpp */
+int osdTimeGetCurrent ( epicsTimeStamp *pDest );
+/* set if/when gtPvt.timeProviders contains more than the default osdTimeGetCurrent() */
+static int gtMoreThanDefault;
+
 /* Implementation */
 
 static void generalTime_InitOnce(void *dummy)
@@ -103,6 +108,9 @@ int generalTimeGetExceptPriority(epicsTimeStamp *pDest, int *pPrio, int ignore)
     gtProvider *ptp;
     int status = S_time_noProvider;
 
+    if(!gtMoreThanDefault)
+        return osdTimeGetCurrent(pDest);
+
     generalTime_Init();
 
     IFDEBUG(2)
@@ -148,6 +156,9 @@ int epicsShareAPI epicsTimeGetCurrent(epicsTimeStamp *pDest)
     int status = S_time_noProvider;
     epicsTimeStamp ts;
 
+    if(!gtMoreThanDefault)
+        return osdTimeGetCurrent(pDest);
+
     generalTime_Init();
 
     IFDEBUG(20)
@@ -370,6 +381,11 @@ static void insertProvider(gtProvider *ptp, ELLLIST *plist, epicsMutexId lock)
         ellAdd(plist, &ptp->node);
     }
 
+    /* Check to see if we have more than just the OS default time source */
+    if(plist==&gtPvt.timeProviders && (ellCount(plist)!=1 || ptp->get.Time!=&osdTimeGetCurrent)) {
+        gtMoreThanDefault = 1;
+    }
+
     epicsMutexUnlock(lock);
 }
 
diff --git a/modules/libcom/src/osi/os/Darwin/osdTime.cpp b/modules/libcom/src/osi/os/Darwin/osdTime.cpp
index 315caeb9b..09471a8e8 100644
--- a/modules/libcom/src/osi/os/Darwin/osdTime.cpp
+++ b/modules/libcom/src/osi/os/Darwin/osdTime.cpp
@@ -26,7 +26,7 @@
 static clock_serv_t host_clock;
 
 extern "C" {
-static int osdTimeGetCurrent (epicsTimeStamp *pDest)
+int osdTimeGetCurrent (epicsTimeStamp *pDest)
 {
     mach_timespec_t mts;
     struct timespec ts;
diff --git a/modules/libcom/src/osi/os/WIN32/osdTime.cpp b/modules/libcom/src/osi/os/WIN32/osdTime.cpp
index 348fe7c2f..1b1a70548 100644
--- a/modules/libcom/src/osi/os/WIN32/osdTime.cpp
+++ b/modules/libcom/src/osi/os/WIN32/osdTime.cpp
@@ -47,7 +47,8 @@
 
 extern "C" void setThreadName ( DWORD dwThreadID, LPCSTR szThreadName );
 
-static int osdTimeGetCurrent ( epicsTimeStamp *pDest );
+extern "C"
+int osdTimeGetCurrent ( epicsTimeStamp *pDest );
 
 // for mingw
 #if !defined ( MAXLONGLONG )
@@ -116,7 +117,7 @@ static int done = timeRegister();
 //
 // osdTimeGetCurrent ()
 //
-static int osdTimeGetCurrent ( epicsTimeStamp *pDest )
+int osdTimeGetCurrent ( epicsTimeStamp *pDest )
 {
     assert ( pCurrentTime );
 
diff --git a/modules/libcom/src/osi/os/posix/osdTime.cpp b/modules/libcom/src/osi/os/posix/osdTime.cpp
index 1952babd9..cc3cb1965 100644
--- a/modules/libcom/src/osi/os/posix/osdTime.cpp
+++ b/modules/libcom/src/osi/os/posix/osdTime.cpp
@@ -32,7 +32,7 @@
         LAST_RESORT_PRIORITY, osdTimeGetCurrent)
 
     extern "C" {
-    static int osdTimeGetCurrent (epicsTimeStamp *pDest)
+    int osdTimeGetCurrent (epicsTimeStamp *pDest)
     {
         struct timeval tv;
         struct timezone tz;
diff --git a/modules/libcom/src/osi/osiClockTime.c b/modules/libcom/src/osi/osiClockTime.c
index b0f4c35eb..bf29427b2 100644
--- a/modules/libcom/src/osi/osiClockTime.c
+++ b/modules/libcom/src/osi/osiClockTime.c
@@ -48,7 +48,7 @@ static epicsThreadOnceId onceId = EPICS_THREAD_ONCE_INIT;
 
 /* Forward references */
 
-static int ClockTimeGetCurrent(epicsTimeStamp *pDest);
+int osdTimeGetCurrent(epicsTimeStamp *pDest);
 
 #if defined(vxWorks) || defined(__rtems__)
 static void ClockTimeSync(void *dummy);
@@ -89,7 +89,7 @@ static void ClockTime_InitOnce(void *pfirst)
 
     /* Register as a time provider */
     generalTimeRegisterCurrentProvider("OS Clock", LAST_RESORT_PRIORITY,
-        ClockTimeGetCurrent);
+        osdTimeGetCurrent);
 }
 
 void ClockTime_Init(int synchronize)
@@ -125,7 +125,7 @@ void ClockTime_Init(int synchronize)
         else {
             /* No synchronization thread */
             if (firstTime)
-                ClockTimeGetCurrent(&ClockTimePvt.startTime);
+                osdTimeGetCurrent(&ClockTimePvt.startTime);
         }
     }
 }
@@ -191,7 +191,7 @@ static void ClockTimeSync(void *dummy)
 
 /* Time Provider Routine */
 
-static int ClockTimeGetCurrent(epicsTimeStamp *pDest)
+int osdTimeGetCurrent(epicsTimeStamp *pDest)
 {
     struct timespec clockNow;