From 7a619addda2eab9c15567b62297a612b1d595f2c Mon Sep 17 00:00:00 2001
From: unknown <karl@E04.petzent.com>
Date: Mon, 29 Sep 2014 22:52:00 -0700
Subject: [PATCH] Add re-entrant WOnly queued lock, remove bt_atomicload

---
 threadskv8.c | 114 ++++++++++++++-------------------------------------
 1 file changed, 31 insertions(+), 83 deletions(-)

diff --git a/threadskv8.c b/threadskv8.c
index 6b37710..3f669b8 100644
--- a/threadskv8.c
+++ b/threadskv8.c
@@ -117,6 +117,8 @@ typedef struct {
 typedef struct {
 	ushort ticket[1];
 	ushort serving[1];
+	ushort tid;
+	ushort dup;
 } WOLock;
 
 #define PHID 0x1
@@ -411,9 +413,14 @@ uid bt_newdup (BtDb *bt)
 
 //	Write-Only Queue Lock
 
-void WriteOLock (WOLock *lock)
+void WriteOLock (WOLock *lock, ushort tid)
 {
 ushort tix;
+
+	if( lock->tid == tid ) {
+		lock->dup++;
+		return;
+	}
 #ifdef unix
 	tix = __sync_fetch_and_add (lock->ticket, 1);
 #else
@@ -427,10 +434,17 @@ ushort tix;
 #else
 		SwitchToThread ();
 #endif
+	lock->tid = tid;
 }
 
 void WriteORelease (WOLock *lock)
 {
+	if( lock->dup ) {
+		lock->dup--;
+		return;
+	}
+
+	lock->tid = 0;
 	lock->serving[0]++;
 }
 
@@ -1168,10 +1182,14 @@ void bt_lockpage(BtDb *bt, BtLock mode, BtLatchSet *latch)
 		WriteLock (latch->access);
 		break;
 	case BtLockParent:
-		WriteOLock (latch->parent);
+		WriteOLock (latch->parent, bt->thread_no);
 		break;
 	case BtLockAtomic:
-		WriteOLock (latch->atomic);
+		WriteOLock (latch->atomic, bt->thread_no);
+		break;
+	case BtLockAtomic | BtLockRead:
+		WriteOLock (latch->atomic, bt->thread_no);
+		ReadLock (latch->readwr);
 		break;
 	}
 }
@@ -1199,6 +1217,10 @@ void bt_unlockpage(BtDb *bt, BtLock mode, BtLatchSet *latch)
 	case BtLockAtomic:
 		WriteORelease (latch->atomic);
 		break;
+	case BtLockAtomic | BtLockRead:
+		WriteORelease (latch->atomic);
+		ReadRelease (latch->readwr);
+		break;
 	}
 }
 
@@ -1569,7 +1591,6 @@ BtKey *ptr;
 
 	bt_unlockpage (bt, BtLockParent, set->latch);
 	bt_unpinlatch (set->latch);
-	bt->found = 1;
 	return 0;
 }
 
@@ -1620,7 +1641,7 @@ BtVal *val;
 	  if( bt_fixfence (bt, set, lvl) )
 		return bt->err;
 	  else
-		return bt->found = found, 0;
+		return 0;
 
 	//	do we need to collapse root?
 
@@ -1628,7 +1649,7 @@ BtVal *val;
 	  if( bt_collapseroot (bt, set) )
 		return bt->err;
 	  else
-		return bt->found = found, 0;
+		return 0;
 
 	//	delete empty page
 
@@ -1638,7 +1659,7 @@ BtVal *val;
 	set->latch->dirty = 1;
 	bt_unlockpage(bt, BtLockWrite, set->latch);
 	bt_unpinlatch (set->latch);
-	return bt->found = found, 0;
+	return 0;
 }
 
 BtKey *bt_foundkey (BtDb *bt)
@@ -2273,79 +2294,6 @@ typedef struct {
 	unsigned char leafkey[BT_keyarray];
 } AtomicKey;
 
-//  find and load leaf page for given key
-//	leave page Atomic locked and Read locked.
-
-int bt_atomicload (BtDb *bt, BtPageSet *set, unsigned char *key, uint len)
-{
-BtLatchSet *prevlatch;
-uid page_no;
-uint slot;
-
-  //  find level one slot
-
-  if( !(slot = bt_loadpage (bt, set, key, len, 1, BtLockRead)) )
-	return 0;
-
-  // find next non-dead entry on this page
-  //	it will be the fence key if nothing else
-
-  while( slotptr(set->page, slot)->dead )
-	if( slot++ < set->page->cnt )
-	  continue;
-	else
-	  return bt->err = BTERR_struct, 0;
-
-  page_no = bt_getid(valptr(set->page, slot)->value);
-  prevlatch = set->latch;
-
-  while( page_no ) {
-	if( set->latch = bt_pinlatch (bt, page_no, 1) )
-	  set->page = bt_mappage (bt, set->latch);
-	else
-	  return 0;
-
- 	// obtain read lock using lock chaining with Access mode
-	//	release & unpin parent/left sibling page
-
-	bt_lockpage(bt, BtLockAccess, set->latch);
-
-	bt_unlockpage(bt, BtLockRead, prevlatch);
-	bt_unpinlatch (prevlatch);
-
-	bt_lockpage(bt, BtLockRead, set->latch);
-
-	//  find key on page at this level
-	//  and descend to requested level
-
-	if( !set->page->kill )
-	 if( !bt_getid (set->page->right) || keycmp (keyptr(set->page, set->page->cnt), key, len) >= 0 ) {
-	  bt_unlockpage(bt, BtLockRead, set->latch);
-	  bt_lockpage(bt, BtLockAtomic, set->latch);
-	  bt_lockpage(bt, BtLockRead, set->latch);
-
-	  if( !set->page->kill )
-	   if( slot = bt_findslot (set->page, key, len) ) {
-	  	bt_unlockpage(bt, BtLockAccess, set->latch);
-		return slot;
-	   }
-
-	  bt_unlockpage(bt, BtLockAtomic, set->latch);
-	  }
-
-	//  slide right into next page
-
-	bt_unlockpage(bt, BtLockAccess, set->latch);
-	page_no = bt_getid(set->page->right);
-	prevlatch = set->latch;
-  }
-
-  // return error on end of right chain
-
-  bt->err = BTERR_struct;
-  return 0;	// return error
-}
-
 //	determine actual page where key is located
 //  return slot number
 
@@ -2589,11 +2537,11 @@ int type;
 	if( samepage = src > 1 )
 	  if( samepage = !bt_getid(set->page->right) || keycmp (keyptr(set->page, set->page->cnt), key->key, key->len) >= 0 )
 		slot = bt_findslot(set->page, key->key, key->len);
-	  else // release read on previous page
+	  else
 	 	bt_unlockpage(bt, BtLockRead, set->latch); 
 
 	if( !slot )
-	  if( slot = bt_atomicload(bt, set, key->key, key->len) )
+	  if( slot = bt_loadpage(bt, set, key->key, key->len, 0, BtLockRead | BtLockAtomic) )
 		set->latch->split = 0;
 	  else
 		return -1;
@@ -2642,7 +2590,7 @@ int type;
 
   //  unlock last loadpage lock
 
-  if( source->cnt > 1 )
+  if( source->cnt )
 	bt_unlockpage(bt, BtLockRead, set->latch);
 
   //  obtain write lock for each master page
-- 
2.40.0