ITS#7364 Limit mdb lock upgrade before sem_unlink.

Do not try shared lock when closing or after error.  Track file lock
state to decide.  Change meaning of *excl to reflect file lock state.

diff --git a/libraries/libmdb/mdb.c b/libraries/libmdb/mdb.c
index 9546d01f4738ef6a4f11c72f8180130da315941f..b00e0767f892c7cb9b7b5178692c6b881bf5add3 100644 (file)
--- a/libraries/libmdb/mdb.c
+++ b/libraries/libmdb/mdb.c
@@ -2775,6 +2775,9 @@ mdb_env_share_locks(MDB_env *env)
        return rc;
 }
 
+/** Try to get exlusive lock, otherwise shared.
+ *     Maintain *excl = -1: no/unknown lock, 0: shared, 1: exclusive.
+ */
 static int
 mdb_env_excl_lock(MDB_env *env, int *excl)
 {
@@ -2798,7 +2801,11 @@ mdb_env_excl_lock(MDB_env *env, int *excl)
        lock_info.l_len = 1;
        if (!fcntl(env->me_lfd, F_SETLK, &lock_info)) {
                *excl = 1;
-       } else {
+       } else
+# ifdef MDB_USE_POSIX_SEM
+       if (*excl < 0) /* always true when !MDB_USE_POSIX_SEM */
+# endif
+       {
                lock_info.l_type = F_RDLCK;
                while ((rc = fcntl(env->me_lfd, F_SETLKW, &lock_info)) &&
                                (rc = ErrCode()) == EINTR) ;
@@ -2896,7 +2903,7 @@ mdb_env_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
        int rc;
        off_t size, rsize;
 
-       *excl = 0;
+       *excl = -1;
 
 #ifdef _WIN32
        if ((env->me_lfd = CreateFile(lpath, GENERIC_READ|GENERIC_WRITE,
@@ -2934,7 +2941,7 @@ mdb_env_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
        size = lseek(env->me_lfd, 0, SEEK_END);
 #endif
        rsize = (env->me_maxreaders-1) * sizeof(MDB_reader) + sizeof(MDB_txninfo);
-       if (size < rsize && *excl) {
+       if (size < rsize && *excl > 0) {
 #ifdef _WIN32
                SetFilePointer(env->me_lfd, rsize, NULL, 0);
                if (!SetEndOfFile(env->me_lfd)) {
@@ -2978,7 +2985,7 @@ mdb_env_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
                env->me_txns = m;
 #endif
        }
-       if (*excl) {
+       if (*excl > 0) {
 #ifdef _WIN32
                BY_HANDLE_FILE_INFORMATION stbuf;
                struct {
@@ -3205,7 +3212,7 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mode_t mode)
                        goto leave;
                }
 #endif
-               if (excl) {
+               if (excl > 0) {
                        rc = mdb_env_share_locks(env);
                        if (rc)
                                goto leave;