From 5eb3b77efe4a596631da7bda3f3a947caee64f26 Mon Sep 17 00:00:00 2001
From: Leonid Yuriev <leo@yuriev.ru>
Date: Sun, 25 Aug 2019 15:56:43 +0300
Subject: [PATCH] mdbx-posix: rework LCK seize/destroy.

---
 src/lck-posix.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/lck-posix.c b/src/lck-posix.c
index afb3e79a..3b931579 100644
--- a/src/lck-posix.c
+++ b/src/lck-posix.c
@@ -152,7 +152,8 @@ int __cold mdbx_lck_seize(MDBX_env *env) {
                        (env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK, 0,
                        OFF_T_MAX);
   if (rc == 0) {
-    /* got dxb-exclusive, try lck-exclusive */
+  continue_exclusive:
+    /* got dxb-exclusive, continue lck-exclusive */
     rc = mdbx_lck_op(env->me_lfd, OP_SETLKW, F_WRLCK, 0, OFF_T_MAX);
     if (rc == 0) {
       /* got both exclusive */
@@ -169,7 +170,14 @@ int __cold mdbx_lck_seize(MDBX_env *env) {
                      (env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK,
                      env->me_pid, 1);
     if (rc == 0) {
-      /* got dxb-shared, try lck-shared */
+      /* got dxb-shared, try again dxb-exclusive */
+      rc = mdbx_lck_op(env->me_fd, OP_SETLK,
+                       (env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK, 0,
+                       OFF_T_MAX);
+      if (rc == 0)
+        goto continue_exclusive;
+
+      /* continue lck-shared */
       rc = mdbx_lck_op(env->me_lfd, OP_SETLKW, F_RDLCK, 0, 1);
       if (rc == 0) {
         /* got both dxb and lck shared lock */
@@ -266,6 +274,9 @@ void __cold mdbx_lck_destroy(MDBX_env *env) {
   if (env->me_lfd != INVALID_HANDLE_VALUE) {
     /* try get exclusive access */
     if (env->me_lck &&
+        mdbx_lck_op(env->me_fd, OP_SETLK,
+                    (env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK, 0,
+                    OFF_T_MAX) == 0 &&
         mdbx_lck_op(env->me_lfd, OP_SETLK, F_WRLCK, 0, OFF_T_MAX) == 0) {
       mdbx_info("%s: got exclusive, drown mutexes", mdbx_func_);
       int rc = pthread_mutex_destroy(&env->me_lck->mti_rmutex);
@@ -273,6 +284,7 @@ void __cold mdbx_lck_destroy(MDBX_env *env) {
         rc = pthread_mutex_destroy(&env->me_lck->mti_wmutex);
       assert(rc == 0);
       (void)rc;
+      msync(env->me_lck, env->me_os_psize, MS_ASYNC);
     }
     (void)mdbx_lck_op(env->me_lfd, OP_SETLK, F_UNLCK, 0, OFF_T_MAX);
   }