branches/5.1: Fix for Bug# 35352. We've added a heuristic that checks

the size of the UNDO slots cache lists (insert and upate). If either of
cached lists has more than 500 entries then we add any UNDO slots that are
freed, to the common free list instead of the cache list, this is to avoid
the case where all the free slots end up in only one of the lists on startup
after a crash.

Tested with test case for 26590 and passes all mysql-test(s).

include/trx0undo.h

@@ -240,6 +240,7 @@ trx_undo_set_state_at_finish(
 /*=========================*/
 				/* out: undo log segment header page,
 				x-latched */
+	trx_rseg_t*	rseg,	/* in: rollback segment memory object */
 	trx_t*		trx,	/* in: transaction */
 	trx_undo_t*	undo,	/* in: undo log memory copy */
 	mtr_t*		mtr);	/* in: mtr */

trx/trx0trx.c

@@ -757,8 +757,8 @@ trx_commit_off_kernel(
 		mutex_enter(&(rseg->mutex));
 
 		if (trx->insert_undo != NULL) {
-			trx_undo_set_state_at_finish(trx, trx->insert_undo,
-						     &mtr);
+			trx_undo_set_state_at_finish(
+				rseg, trx, trx->insert_undo, &mtr);
 		}
 
 		undo = trx->update_undo;
@@ -774,7 +774,7 @@ trx_commit_off_kernel(
 			transaction commit for this transaction. */
 
 			update_hdr_page = trx_undo_set_state_at_finish(
-				trx, undo, &mtr);
+				rseg, trx, undo, &mtr);
 
 			/* We have to do the cleanup for the update log while
 			holding the rseg mutex because update log headers

trx/trx0undo.c

@@ -1725,6 +1725,7 @@ trx_undo_set_state_at_finish(
 /*=========================*/
 				/* out: undo log segment header page,
 				x-latched */
+	trx_rseg_t*	rseg,	/* in: rollback segment memory object */
 	trx_t*		trx __attribute__((unused)), /* in: transaction */
 	trx_undo_t*	undo,	/* in: undo log memory copy */
 	mtr_t*		mtr)	/* in: mtr */
@@ -1734,7 +1735,10 @@ trx_undo_set_state_at_finish(
 	page_t*		undo_page;
 	ulint		state;
 
-	ut_ad(trx && undo && mtr);
+	ut_ad(trx);
+	ut_ad(undo);
+	ut_ad(mtr);
+	ut_ad(mutex_own(&rseg->mutex));
 
 	if (undo->id >= TRX_RSEG_N_SLOTS) {
 		fprintf(stderr, "InnoDB: Error: undo->id is %lu\n",
@@ -1748,9 +1752,23 @@ trx_undo_set_state_at_finish(
 	seg_hdr = undo_page + TRX_UNDO_SEG_HDR;
 	page_hdr = undo_page + TRX_UNDO_PAGE_HDR;
 
-	if (undo->size == 1 && mach_read_from_2(page_hdr + TRX_UNDO_PAGE_FREE)
-	    < TRX_UNDO_PAGE_REUSE_LIMIT) {
-		state = TRX_UNDO_CACHED;
+	if (undo->size == 1
+	    && mach_read_from_2(page_hdr + TRX_UNDO_PAGE_FREE)
+	       < TRX_UNDO_PAGE_REUSE_LIMIT) {
+
+		/* This is a heuristic to avoid the problem of all UNDO
+		slots ending up in one of the UNDO lists. Previously if
+		the server crashed with all the slots in one of the lists,
+		transactions that required the slots of a different type
+		would fail for lack of slots. */
+
+		if (UT_LIST_GET_LEN(rseg->update_undo_list) < 500
+		    && UT_LIST_GET_LEN(rseg->insert_undo_list) < 500) {
+
+			state = TRX_UNDO_CACHED;
+		} else {
+			state = TRX_UNDO_TO_FREE;
+		}
 
 	} else if (undo->type == TRX_UNDO_INSERT) {