Bug fixes in lock code.

[tlwilmar]

Summary

(Parts of this change were already applied to LLVM code base.)

This change set fixes two bugs in the lock code.

1. Misplaced switch target in the __kmp_get_user_lock_owner function found by LLVM user
2. Use of incorrect time-stamp counter in the __kmp_spin_backoff function for non-Intel architecture, found by Jim

A new utility function kmp_now_nsec() was added for the second item,
and code for handling wrap-around counters (provided by Jim) was also
added for the kmp_spin_backoff function.

Patch by Hansang Bae

runtime/src/kmp_lock.cpp

 __kmp_set_drdpa_lock_flags( kmp_drdpa_lock_t *lck, kmp_lock_flags_t flags )
 {
     lck->lk.flags = flags;
 }
 
 // Time stamp counter
 #if KMP_ARCH_X86 || KMP_ARCH_X86_64
 # define __kmp_tsc() __kmp_hardware_timestamp()
-// Runtime's default backoff parameters
-kmp_backoff_t __kmp_spin_backoff_params = { 1, 4096, 100 };
-#else
+#elif KMP_OS_LINUX
   // Use nanoseconds for other platforms
   extern kmp_uint64 __kmp_now_nsec();
-kmp_backoff_t __kmp_spin_backoff_params = { 1, 256, 100 };
 # define __kmp_tsc() __kmp_now_nsec()
+#else
+# error time stamp counter is not supported
 #endif
 
 // A useful predicate for dealing with timestamps that may wrap.
 // Is a before b?
 // Since the timestamps may wrap, this is asking whether it's
 // shorter to go clockwise from a to b around the clock-face, or anti-clockwise.
 // Times where going clockwise is less distance than going anti-clockwise
 // are in the future, others are in the past.
 // e.g.) a = MAX-1, b = MAX+1 (=0), then a > b (true) does not mean a reached b
 //       whereas signed(a) = -2, signed(b) = 0 captures the actual difference
 static inline bool before(kmp_uint64 a, kmp_uint64 b)
 {
     return ((kmp_int64)b - (kmp_int64)a) > 0;
 }
 
+// Runtime's default backoff parameters
+kmp_backoff_t __kmp_spin_backoff_params = { 1, 4096, 100 };
+
 // Truncated binary exponential backoff function
 void
 __kmp_spin_backoff(kmp_backoff_t *boff)
 {
     // We could flatten this loop, but making it a nested loop gives better result.
     kmp_uint32 i;
     for (i = boff->step; i > 0; i--) {
         kmp_uint64 goal = __kmp_tsc() + boff->min_tick;

runtime/src/z_Linux_util.c

 
 /* Calculate the elapsed wall clock tick for the user */
 void
 __kmp_elapsed_tick( double *t )
 {
     *t = 1 / (double) CLOCKS_PER_SEC;
 }
 
+#if KMP_OS_LINUX
 /* Return the current time stamp in nsec */
 kmp_uint64
 __kmp_now_nsec()
 {
-    struct timeval t;
-    gettimeofday(&t, NULL);
-    return KMP_NSEC_PER_SEC*t.tv_sec + 1000*t.tv_usec;
+    struct timespec t;
+    clock_gettime(CLOCK_MONOTONIC, &t);
+    return 1e9*t.tv_sec + t.tv_nsec;
 }
+#endif
 
 /*
     Determine whether the given address is mapped into the current address space.
 */
 
 int
 __kmp_is_address_mapped( void * addr ) {