Final spinlock tidying-up

* Abort epicsSpinTest() if epicsSpinCreate() returns NULL
* Adjust RELEASE_NOTES that describe the implementations.

documentation/RELEASE_NOTES.html

@@ -117,12 +117,13 @@ The basic rules which device support must follow are:</p>
 <p>The new header file epicsSpin.h adds a portable spin-locks API which is
 intended for locking very short sections of code (typically one or two lines of
 C or C++) to provide a critical section that protects against race conditions.
-On Posix platforms this uses the pthread_spinlock_t type if it's available but
-falls back to a pthread_mutex_t if not; on the UP VxWorks and RTEMS platforms
-the implementations lock out the CPU interrupts; the default implementation
-(used where no better implementation is available for the platform) uses an
-epicsMutex. Spin-locks may not be taken recursively, and the code inside the
-critical section should always be short and deterministic.</p>
+On Posix platforms this uses the pthread_spinlock_t type if it's available and
+the build is not configured to use Posix thread priorities, but otherwise it
+falls back to a pthread_mutex_t. On the UP VxWorks and RTEMS platforms the
+implementations lock out CPU interrupts and disable task preemption while a
+spin-lock is held. The default implementation (used when no other implementation
+is provided) uses an epicsMutex. Spin-locks may not be taken recursively, and
+the code inside the critical section should be short and deterministic.</p>
 
 <h3>Improvements to aToIPAddr()</h3>
 

src/libCom/test/epicsSpinTest.c

@@ -94,6 +94,8 @@ void epicsSpinPerformance ()
 
     /* Initialize spinlock */
     spin = epicsSpinCreate();
+    if (!spin)
+        testAbort("epicsSpinCreate() returned NULL");
 
     /* test a single lock pair */
     epicsTimeGetCurrent(&begin);
@@ -126,7 +128,7 @@ static void verifyTryLock()
 {
     struct verifyTryLock verify;
 
-    verify.spin = epicsSpinCreate();
+    verify.spin = epicsSpinMustCreate();
     verify.done = epicsEventMustCreate(epicsEventEmpty);
 
     testOk1(epicsSpinTryLock(verify.spin) == 0);
@@ -159,6 +161,8 @@ MAIN(epicsSpinTest)
     verifyTryLock();
 
     spin = epicsSpinCreate();
+    if (!spin)
+        testAbort("epicsSpinCreate() returned NULL");
 
     id = (epicsThreadId *) calloc(nthreads, sizeof(epicsThreadId));
     name = (char **) calloc(nthreads, sizeof(char *));