ck_backoff: Replace ck_backoff_eb with ck_backoff_gb.

The distinction between additive/exponential implementation
and geometric implementation does little but confuse users.
The terminology used in ck_backoff now reflects terminology
used in literature.

ck_backoff_gb has been removed.

include/ck_backoff.h

@@ -38,7 +38,7 @@
 typedef volatile unsigned int ck_backoff_t;
 
 /*
- * This is an exponential back-off implementation.
+ * This is a exponential back-off implementation.
  */
 CK_CC_INLINE static void
 ck_backoff_eb(volatile unsigned int *c)
@@ -50,27 +50,6 @@ ck_backoff_eb(volatile unsigned int *c)
 
 	for (i = 0; i < ceiling; i++);
 
-	ceiling *= ceiling;
-	ceiling &= CK_BACKOFF_CEILING;
-	ceiling += CK_BACKOFF_INITIALIZER;
-
-	*c = ceiling;
-	return;
-}
-
-/*
- * This is a geometric back-off implementation.
- */
-CK_CC_INLINE static void
-ck_backoff_gb(volatile unsigned int *c)
-{
-	volatile unsigned int i;
-	unsigned int ceiling;
-
-	ceiling = *c;
-
-	for (i = 0; i < ceiling; i++);
-
 	*c = ceiling <<= ceiling < CK_BACKOFF_CEILING;
 	return;
 }

regressions/ck_backoff/validate/validate.c

@@ -41,8 +41,9 @@ main(void)
 
 	for (;;) {
 		ck_backoff_t previous = backoff;
-		ck_backoff_gb(&backoff);
+		ck_backoff_eb(&backoff);
 
+		printf("EB %u\n", backoff);
 		if (previous == ceiling) {
 			if (backoff != ceiling)
 				ck_error("[C] GB: expected %u, got %u\n", ceiling, backoff);
@@ -54,19 +55,6 @@ main(void)
 		}
 	}
 
-	backoff = CK_BACKOFF_INITIALIZER;
-	for (;;) {
-		ck_backoff_t previous = backoff;
-		ck_backoff_eb(&backoff);
-
-		if (backoff = previous) {
-			if (i++ >= 3)
-				break;
-		} else if (previous * previous >= backoff) {
-			ck_error("[N] EB: expected %u (%u), got %u\n", previous * previous, previous, backoff);
-		}
-	}
-
 	return 0;
 }
 

src/ck_hp.c

@@ -316,7 +316,7 @@ ck_hp_purge(struct ck_hp_record *thread)
 	while (thread->n_pending > 0) {
 		ck_hp_reclaim(thread);
 		if (thread->n_pending > 0)
-			ck_backoff_gb(&backoff);
+			ck_backoff_eb(&backoff);
 	}
 
 	return;