-/* -----------------------------------------------------------------------------
- * Locking/unlocking closures
- *
- * This is used primarily in the implementation of MVars.
- * -------------------------------------------------------------------------- */
-
-#define SPIN_COUNT 4000
-
-INLINE_HEADER StgInfoTable *
-lockClosure(StgClosure *p)
-{
- StgWord info;
- do {
- nat i = 0;
- do {
- info = xchg((P_)(void *)&p->header.info, (W_)&stg_WHITEHOLE_info);
- if (info != (W_)&stg_WHITEHOLE_info) return (StgInfoTable *)info;
- } while (++i < SPIN_COUNT);
- yieldThread();
- } while (1);
-}
-
-INLINE_HEADER void
-unlockClosure(StgClosure *p, StgInfoTable *info)
-{
- // This is a strictly ordered write, so we need a write_barrier():
- write_barrier();
- p->header.info = info;
-}
-
-/* -----------------------------------------------------------------------------
- * Spin locks
- *
- * These are simple spin-only locks as opposed to Mutexes which
- * probably spin for a while before blocking in the kernel. We use
- * these when we are sure that all our threads are actively running on
- * a CPU, eg. in the GC.
- *
- * TODO: measure whether we really need these, or whether Mutexes
- * would do (and be a bit safer if a CPU becomes loaded).
- * -------------------------------------------------------------------------- */
-
-#if defined(DEBUG)
-typedef struct StgSync_
-{
- StgWord32 lock;
- StgWord64 spin; // DEBUG version counts how much it spins
-} StgSync;
-#else
-typedef StgWord StgSync;
-#endif
-
-typedef lnat StgSyncCount;
-
-
-#if defined(DEBUG)
-
-// Debug versions of spin locks maintain a spin count
-
-// How to use:
-// To use the debug veriosn of the spin locks, a debug version of the program
-// can be run under a deugger with a break point on stat_exit. At exit time
-// of the program one can examine the state the spin count counts of various
-// spin locks to check for contention.
-
-// acquire spin lock
-INLINE_HEADER void acquireSpinLock(StgSync * p)
-{
- StgWord32 r = 0;
- do {
- p->spin++;
- r = cas((StgVolatilePtr)&(p->lock), 1, 0);
- } while(r == 0);
- p->spin--;
-}
-
-// release spin lock
-INLINE_HEADER void releaseSpinLock(StgSync * p)
-{
- write_barrier();
- p->lock = 1;
-}
-
-// initialise spin lock
-INLINE_HEADER void initSpinLock(StgSync * p)
-{
- write_barrier();
- p->lock = 1;
- p->spin = 0;
-}
-
-#else
-
-// acquire spin lock
-INLINE_HEADER void acquireSpinLock(StgSync * p)
-{
- StgWord32 r = 0;
- do {
- r = cas((StgVolatilePtr)p, 1, 0);
- } while(r == 0);
-}
-
-// release spin lock
-INLINE_HEADER void releaseSpinLock(StgSync * p)
-{
- write_barrier();
- (*p) = 1;
-}
-
-// init spin lock
-INLINE_HEADER void initSpinLock(StgSync * p)
-{
- write_barrier();
- (*p) = 1;
-}
-
-#endif /* DEBUG */
-