ETS: Fix valgrind PossiblyLost in ETS hash tables

Add an extra pointer to start of segment with the active segment table
to get rid of PossiblyLost errors without the need of a too general
suppression that may hide real memory leaks in ETS.

2 files changed, 19 insertions, 5 deletions

diff --git a/erts/emulator/beam/erl_db_hash.c b/erts/emulator/beam/erl_db_hash.c
index e3380a57b2..2428ba655a 100644
--- a/erts/emulator/beam/erl_db_hash.c
+++ b/erts/emulator/beam/erl_db_hash.c
@@ -314,13 +314,23 @@ struct ext_segment {
 #define SIZEOF_EXTSEG(NSEGS) \
     (sizeof(struct ext_segment) - sizeof(struct segment*) + sizeof(struct segment*)*(NSEGS))
 
-#ifdef DEBUG
+#if defined(DEBUG) || defined(VALGRIND)
 #  include <stddef.h> /* offsetof */
 #  define EXTSEG(SEGTAB_PTR) \
     ((struct ext_segment*) (((char*)(SEGTAB_PTR)) - offsetof(struct ext_segment,segtab)))
 #endif
 
 
+static ERTS_INLINE void SET_SEGTAB(DbTableHash* tb,
+				   struct segment** segtab)
+{
+    erts_smp_atomic_set_wb(&tb->segtab, (erts_aint_t) segtab);
+#ifdef VALGRIND
+    tb->top_ptr_to_segment_with_active_segtab = EXTSEG(segtab);
+#endif
+}
+
+
 /* How the table segments relate to each other:
 
     ext_segment:                      ext_segment:              "plain" segment
@@ -649,7 +659,8 @@ int db_create_hash(Process *p, DbTable *tbl)
     erts_smp_atomic_init_nob(&tb->szm, SEGSZ_MASK);
     erts_smp_atomic_init_nob(&tb->nactive, SEGSZ);
     erts_smp_atomic_init_nob(&tb->fixdel, (erts_aint_t)NULL);
-    erts_smp_atomic_init_nob(&tb->segtab, (erts_aint_t) alloc_ext_seg(tb,0,NULL)->segtab);
+    erts_smp_atomic_init_nob(&tb->segtab, (erts_aint_t)NULL);
+    SET_SEGTAB(tb, alloc_ext_seg(tb,0,NULL)->segtab);
     tb->nsegs = NSEG_1;
     tb->nslots = SEGSZ;
 
@@ -2357,7 +2368,7 @@ static int alloc_seg(DbTableHash *tb)
 	    struct ext_segment* eseg;
 	    eseg = (struct ext_segment*) SEGTAB(tb)[seg_ix-1];
 	    MY_ASSERT(eseg!=NULL && eseg->s.is_ext_segment);
-	    erts_smp_atomic_set_wb(&tb->segtab, (erts_aint_t) eseg->segtab);
+	    SET_SEGTAB(tb, eseg->segtab);	    
 	    tb->nsegs = eseg->nsegs;
 	}
 	ASSERT(seg_ix < tb->nsegs);
@@ -2429,7 +2440,7 @@ static int free_seg(DbTableHash *tb, int free_records)
 	    MY_ASSERT(newtop->s.is_ext_segment);
 	    if (newtop->prev_segtab != NULL) {
 		/* Time to use a smaller segtab */
-		erts_smp_atomic_set_wb(&tb->segtab, (erts_aint_t)newtop->prev_segtab);
+		SET_SEGTAB(tb, newtop->prev_segtab);
 		tb->nsegs = seg_ix;
 		ASSERT(tb->nsegs == EXTSEG(SEGTAB(tb))->nsegs);
 	    }
@@ -2446,7 +2457,7 @@ static int free_seg(DbTableHash *tb, int free_records)
     if (seg_ix > 0) {
 	if (seg_ix < tb->nsegs) SEGTAB(tb)[seg_ix] = NULL;
     } else {
-	erts_smp_atomic_set_wb(&tb->segtab, (erts_aint_t)NULL);
+	SET_SEGTAB(tb, NULL);
     }
 #endif
     tb->nslots -= SEGSZ;
diff --git a/erts/emulator/beam/erl_db_hash.h b/erts/emulator/beam/erl_db_hash.h
index e0285fa5ed..23ac493118 100644
--- a/erts/emulator/beam/erl_db_hash.h
+++ b/erts/emulator/beam/erl_db_hash.h
@@ -58,6 +58,9 @@ typedef struct db_table_hash {
 #ifdef ERTS_SMP
     DbTableHashFineLocks* locks;
 #endif
+#ifdef VALGRIND
+    struct ext_segment* top_ptr_to_segment_with_active_segtab;
+#endif
 } DbTableHash;