From 8fec9d6e003da8274a9225f013ef76a39bdbd869 Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@bnl.gov>
Date: Fri, 25 Jul 2014 15:12:02 -0400
Subject: [PATCH] epicsSpin: try lock return non-blocking

Avoid cantProceed() in try lock, even for undefined behavior.
---
 src/libCom/osi/os/RTEMS/osdSpin.c   | 13 +++++++++++--
 src/libCom/osi/os/vxWorks/osdSpin.c | 12 +++++++++++-
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/libCom/osi/os/RTEMS/osdSpin.c b/src/libCom/osi/os/RTEMS/osdSpin.c
index 1d5a1d108..f2587f76d 100644
--- a/src/libCom/osi/os/RTEMS/osdSpin.c
+++ b/src/libCom/osi/os/RTEMS/osdSpin.c
@@ -59,7 +59,6 @@ void epicsSpinLock(epicsSpinId spin) {
     rtems_interrupt_level level;
     rtems_interrupt_disable (level);
     _Thread_Disable_dispatch();
-    spin->level = level;
     if(spin->locked) {
         rtems_interrupt_enable (level);
         _Thread_Enable_dispatch();
@@ -71,11 +70,21 @@ void epicsSpinLock(epicsSpinId spin) {
         }
         return;
     }
+    spin->level = level;
     spin->locked = 1;
 }
 
 int epicsSpinTryLock(epicsSpinId spin) {
-    epicsSpinLock(spin);
+    rtems_interrupt_level level;
+    rtems_interrupt_disable (level);
+    _Thread_Disable_dispatch();
+    if(spin->locked) {
+        rtems_interrupt_enable (level);
+        _Thread_Enable_dispatch();
+        return 1;
+    }
+    spin->level = level;
+    spin->locked = 1;
     return 0;
 }
 
diff --git a/src/libCom/osi/os/vxWorks/osdSpin.c b/src/libCom/osi/os/vxWorks/osdSpin.c
index 06cb73c63..97d490916 100644
--- a/src/libCom/osi/os/vxWorks/osdSpin.c
+++ b/src/libCom/osi/os/vxWorks/osdSpin.c
@@ -71,7 +71,17 @@ void epicsSpinLock(epicsSpinId spin) {
 }
 
 int epicsSpinTryLock(epicsSpinId spin) {
-    epicsSpinLock(spin);
+    int key = intLock();
+    if(!intContext())
+        taskLock();
+    if(spin->locked) {
+        intUnlock(key);
+        if(!intContext())
+            taskUnlock();
+        return 1;
+    }
+    spin->key = key;
+    spin->locked = 1;
     return 0;
 }