mdbx: use mdbx_jitter4testing() for race detection.

src/bits.h

@@ -815,8 +815,11 @@ int mdbx_reader_check0(MDB_env *env, int rlocked, int *dead);
   (&((MDB_metabuf *)((env)->me_map + env->me_psize))->mb_metabuf.mm_meta)
 
 static __inline MDB_meta *mdbx_meta_head(MDB_env *env) {
+  mdbx_jitter4testing(true);
   MDB_meta *a = METAPAGE_1(env);
+  mdbx_jitter4testing(true);
   MDB_meta *b = METAPAGE_2(env);
+  mdbx_jitter4testing(true);
 
   return (a->mm_txnid > b->mm_txnid) ? a : b;
 }

src/lck-windows.c

@@ -193,7 +193,7 @@ static int internal_seize_lck(HANDLE lfd) {
   assert(lfd != INVALID_HANDLE_VALUE);
 
   /* 1) now on ?-? (free), get ?-E (middle) */
-  jitter4testing();
+  mdbx_jitter4testing(false);
   if (!flock(lfd, LCK_EXCLUSIVE | LCK_WAITFOR, LCK_UPPER)) {
     rc = GetLastError() /* 2) something went wrong, give up */;
     mdbx_error("%s(%s) failed: errcode %u", mdbx_func_,
@@ -202,13 +202,13 @@ static int internal_seize_lck(HANDLE lfd) {
   }
 
   /* 3) now on ?-E (middle), try E-E (exclusive) */
-  jitter4testing();
+  mdbx_jitter4testing(false);
   if (flock(lfd, LCK_EXCLUSIVE | LCK_DONTWAIT, LCK_LOWER))
     return MDBX_RESULT_TRUE; /* 4) got E-E (exclusive), done */
 
   /* 5) still on ?-E (middle) */
   rc = GetLastError();
-  jitter4testing();
+  mdbx_jitter4testing(false);
   if (rc != ERROR_SHARING_VIOLATION && rc != ERROR_LOCK_VIOLATION) {
     /* 6) something went wrong, give up */
     if (!funlock(lfd, LCK_UPPER)) {
@@ -220,11 +220,11 @@ static int internal_seize_lck(HANDLE lfd) {
   }
 
   /* 7) still on ?-E (middle), try S-E (locked) */
-  jitter4testing();
+  mdbx_jitter4testing(false);
   rc = flock(lfd, LCK_SHARED | LCK_DONTWAIT, LCK_LOWER) ? MDBX_RESULT_FALSE
                                                         : GetLastError();
 
-  jitter4testing();
+  mdbx_jitter4testing(false);
   if (rc != MDBX_RESULT_FALSE)
     mdbx_error("%s(%s) failed: errcode %u", mdbx_func_,
                "?-E(middle) >> S-E(locked)", rc);
@@ -247,7 +247,7 @@ int mdbx_lck_seize(MDB_env *env) {
   assert(env->me_fd != INVALID_HANDLE_VALUE);
   if (env->me_lfd == INVALID_HANDLE_VALUE) {
     /* LY: without-lck mode (e.g. on read-only filesystem) */
-    jitter4testing();
+    mdbx_jitter4testing(false);
     if (!flock(env->me_fd, LCK_SHARED | LCK_DONTWAIT, LCK_WHOLE)) {
       rc = GetLastError();
       mdbx_error("%s(%s) failed: errcode %u", mdbx_func_, "without-lck", rc);
@@ -257,7 +257,7 @@ int mdbx_lck_seize(MDB_env *env) {
   }
 
   rc = internal_seize_lck(env->me_lfd);
-  jitter4testing();
+  mdbx_jitter4testing(false);
   if (rc == MDBX_RESULT_TRUE && (env->me_flags & MDB_RDONLY) == 0) {
     /* Check that another process don't operates in without-lck mode.
      * Doing such check by exclusive locking the body-part of db. Should be
@@ -269,10 +269,10 @@ int mdbx_lck_seize(MDB_env *env) {
       rc = GetLastError();
       mdbx_error("%s(%s) failed: errcode %u", mdbx_func_,
                  "lock-against-without-lck", rc);
-      jitter4testing();
+      mdbx_jitter4testing(false);
       mdbx_lck_destroy(env);
     } else {
-      jitter4testing();
+      mdbx_jitter4testing(false);
       if (!funlock(env->me_fd, LCK_BODY)) {
         rc = GetLastError();
         mdbx_panic("%s(%s) failed: errcode %u", mdbx_func_,

src/mdbx.c

@@ -1412,6 +1412,7 @@ static txnid_t mdbx_find_oldest(MDB_env *env, int *laggard) {
   const MDB_reader *const r = env->me_lck->mti_readers;
   for (reader = -1, i = env->me_lck->mti_numreaders; --i >= 0;) {
     if (r[i].mr_pid) {
+      mdbx_jitter4testing(true);
       txnid_t snap = r[i].mr_txnid;
       if (oldest > snap) {
         oldest = snap;
@@ -2187,9 +2188,13 @@ static int mdbx_txn_renew0(MDB_txn *txn, unsigned flags) {
 
     while (1) {
       MDB_meta *const meta = mdbx_meta_head(txn->mt_env);
+      mdbx_jitter4testing(false);
       const txnid_t snap = meta->mm_txnid;
+      mdbx_jitter4testing(false);
       r->mr_txnid = snap;
+      mdbx_jitter4testing(false);
       mdbx_coherent_barrier();
+      mdbx_jitter4testing(true);
 
       /* Snap the state from current meta-head */
       txn->mt_txnid = snap;
@@ -2206,21 +2211,16 @@ static int mdbx_txn_renew0(MDB_txn *txn, unsigned flags) {
     txn->mt_dbxs = env->me_dbxs; /* mostly static anyway */
   } else {
     /* Not yet touching txn == env->me_txn0, it may be active */
+    mdbx_jitter4testing(false);
     rc = mdbx_txn_lock(env);
     if (unlikely(rc))
       return rc;
 
+    mdbx_jitter4testing(false);
     MDB_meta *meta = mdbx_meta_head(env);
+    mdbx_jitter4testing(false);
     txn->mt_canary = meta->mm_canary;
     txn->mt_txnid = meta->mm_txnid + 1;
-    if (unlikely(txn->mt_txnid < meta->mm_txnid)) {
-      mdbx_debug("txnid overflow!");
-      rc = MDB_TXN_FULL;
-      goto bailout;
-    }
-
-    txn->mt_flags = flags;
-
 #if MDB_DEBUG
     if (unlikely(txn->mt_txnid == mdbx_debug_edge)) {
       if (!mdbx_debug_logger)
@@ -2230,6 +2230,13 @@ static int mdbx_txn_renew0(MDB_txn *txn, unsigned flags) {
                      "on/off edge (txn %zu)", txn->mt_txnid);
     }
 #endif
+    if (unlikely(txn->mt_txnid < meta->mm_txnid)) {
+      mdbx_debug("txnid overflow!");
+      rc = MDB_TXN_FULL;
+      goto bailout;
+    }
+
+    txn->mt_flags = flags;
     txn->mt_child = NULL;
     txn->mt_loose_pgs = NULL;
     txn->mt_loose_count = 0;
@@ -3834,6 +3841,13 @@ static int __cold mdbx_setup_lck(MDB_env *env, char *lck_pathname, int mode) {
     off_t wanna = roundup2((env->me_maxreaders - 1) * sizeof(MDB_reader) +
                                sizeof(MDBX_lockinfo),
                            env->me_os_psize);
+#ifndef NDEBUG
+    err = mdbx_ftruncate(env->me_lfd, size = 0);
+    if (unlikely(err != MDB_SUCCESS))
+      return err;
+#endif
+    mdbx_jitter4testing(false);
+
     if (size != wanna) {
       err = mdbx_ftruncate(env->me_lfd, wanna);
       if (unlikely(err != MDB_SUCCESS))