Make SysV semaphores robust. Cleanup MDB_ROBUST.

diff --git a/libraries/liblmdb/lmdb.h b/libraries/liblmdb/lmdb.h
index 9efdfb39630105634d13befd040e55142054a75b..f37d8f589710c34433fd290350fb8f9e7dc99680 100644 (file)
--- a/libraries/liblmdb/lmdb.h
+++ b/libraries/liblmdb/lmdb.h
@@ -109,7 +109,9 @@
  *       The transaction becomes "long-lived" as above until a check
  *       for stale readers is performed or the lockfile is reset,
  *       since the process may not remove it from the lockfile.
- *       Except write-transactions on Unix with MDB_ROBUST or on Windows.
+ *
+ *       This does not apply to write transactions if the system clears
+ *       stale writers, see above.
  *
  *     - If you do that anyway, do a periodic check for stale readers. Or
  *       close the environment once in a while, so the lockfile can get reset.

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 84cd8a35a0bfdcd9253f7f3cd12be23e83c782e3..f0fe6154b2a63c9e06eb829e9d395dc1908f9e77 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -208,7 +208,7 @@ union semun {
 #define MDB_DEVEL 0
 #endif
 
-#if defined(_WIN32) || (defined(EOWNERDEAD) && !defined(MDB_USE_SYSV_SEM))
+#if defined(_WIN32) || defined(MDB_USE_SYSV_SEM) || defined(EOWNERDEAD)
 #define MDB_ROBUST_SUPPORTED   1
 #endif
 
@@ -222,6 +222,16 @@ union semun {
 # define mdb_func_     "<mdb_unknown>"
 #endif
 
+/* Internal error codes, not exposed outside liblmdb */
+#define        MDB_NO_ROOT             (MDB_LAST_ERRCODE + 10)
+#ifdef _WIN32
+#define MDB_OWNERDEAD  ((int) WAIT_ABANDONED)
+#elif defined MDB_USE_SYSV_SEM
+#define MDB_OWNERDEAD  (MDB_LAST_ERRCODE + 11)
+#else
+#define MDB_OWNERDEAD  EOWNERDEAD
+#endif
+
 #ifdef _WIN32
 #define MDB_USE_HASH   1
 #define MDB_PIDLOCK    0
@@ -237,7 +247,6 @@ typedef HANDLE mdb_mutex_t;
 #define pthread_key_delete(x)  TlsFree(x)
 #define pthread_getspecific(x) TlsGetValue(x)
 #define pthread_setspecific(x,y)       (TlsSetValue(x,y) ? 0 : ErrCode())
-#define pthread_mutex_consistent(mutex) 0
 #define pthread_mutex_unlock(x)        ReleaseMutex(*x)
 #define pthread_mutex_lock(x)  WaitForSingleObject(*x, INFINITE)
 #define pthread_cond_signal(x) SetEvent(*x)
@@ -247,6 +256,7 @@ typedef HANDLE mdb_mutex_t;
 #define MDB_MUTEX(env, rw)             ((env)->me_##rw##mutex)
 #define LOCK_MUTEX0(mutex)             WaitForSingleObject(mutex, INFINITE)
 #define UNLOCK_MUTEX(mutex)            ReleaseMutex(mutex)
+#define mdb_mutex_consistent(mutex)    0
 #define getpid()       GetCurrentProcessId()
 #define        MDB_FDATASYNC(fd)       (!FlushFileBuffers(fd))
 #define        MDB_MSYNC(addr,len,flags)       (!FlushViewOfFile(addr,len))
@@ -274,6 +284,7 @@ typedef HANDLE mdb_mutex_t;
 typedef struct mdb_mutex {
        int semid;
        int semnum;
+       int *locked;
 } mdb_mutex_t;
 
 #define MDB_MUTEX(env, rw)             (&(env)->me_##rw##mutex)
@@ -281,19 +292,28 @@ typedef struct mdb_mutex {
 #define UNLOCK_MUTEX(mutex)            do { \
        struct sembuf sb = { 0, 1, SEM_UNDO }; \
        sb.sem_num = (mutex)->semnum; \
+       *(mutex)->locked = 0; \
        semop((mutex)->semid, &sb, 1); \
 } while(0)
 
 static int
 mdb_sem_wait(mdb_mutex_t *sem)
 {
-   int rc;
-   struct sembuf sb = { 0, -1, SEM_UNDO };
-   sb.sem_num = sem->semnum;
-   while ((rc = semop(sem->semid, &sb, 1)) && (rc = errno) == EINTR) ;
-   return rc;
+       int rc, *locked = sem->locked;
+       struct sembuf sb = { 0, -1, SEM_UNDO };
+       sb.sem_num = sem->semnum;
+       do {
+               if (!semop(sem->semid, &sb, 1)) {
+                       rc = *locked ? MDB_OWNERDEAD : MDB_SUCCESS;
+                       *locked = 1;
+                       break;
+               }
+       } while ((rc = errno) == EINTR);
+       return rc;
 }
 
+#define mdb_mutex_consistent(mutex)    0
+
 #else
        /** Pointer/HANDLE type of shared mutex/semaphore.
         */
@@ -308,6 +328,9 @@ typedef pthread_mutex_t mdb_mutex_t;
        /** Unlock the reader or writer mutex.
         */
 #define UNLOCK_MUTEX(mutex)    pthread_mutex_unlock(mutex)
+       /** Mark mutex-protected data as repaired, after death of previous owner.
+        */
+#define mdb_mutex_consistent(mutex)    pthread_mutex_consistent(mutex)
 #endif /* MDB_USE_SYSV_SEM */
 
        /** Get the error code for the last failed system function.
@@ -336,11 +359,17 @@ typedef pthread_mutex_t mdb_mutex_t;
 #if defined(_WIN32)
 #define MNAME_LEN      32
 #elif defined(MDB_USE_SYSV_SEM)
-#define MNAME_LEN      0
+#define MNAME_LEN      (sizeof(int))
 #else
 #define MNAME_LEN      (sizeof(pthread_mutex_t))
 #endif
 
+#ifdef MDB_USE_SYSV_SEM
+#define SYSV_SEM_FLAG  1               /**< SysV sems in lockfile format */
+#else
+#define SYSV_SEM_FLAG  0
+#endif
+
 /** @} */
 
 #ifdef MDB_ROBUST_SUPPORTED
@@ -667,6 +696,7 @@ typedef struct MDB_txbody {
        char    mtb_rmname[MNAME_LEN];
 #elif defined(MDB_USE_SYSV_SEM)
        int     mtb_semid;
+       int             mtb_rlocked;
 #else
                /** Mutex protecting access to this table.
                 *      This is the #MDB_MUTEX(env,r) reader table lock.
@@ -695,22 +725,25 @@ typedef struct MDB_txninfo {
 #define mti_rmname     mt1.mtb.mtb_rmname
 #define mti_txnid      mt1.mtb.mtb_txnid
 #define mti_numreaders mt1.mtb.mtb_numreaders
-               char pad[(sizeof(MDB_txbody)+CACHELINE-1) & ~(CACHELINE-1)];
-       } mt1;
 #ifdef MDB_USE_SYSV_SEM
 #define        mti_semid       mt1.mtb.mtb_semid
-#else
+#define        mti_rlocked     mt1.mtb.mtb_rlocked
+#endif
+               char pad[(sizeof(MDB_txbody)+CACHELINE-1) & ~(CACHELINE-1)];
+       } mt1;
        union {
 #if defined(_WIN32)
                char mt2_wmname[MNAME_LEN];
 #define        mti_wmname      mt2.mt2_wmname
+#elif defined MDB_USE_SYSV_SEM
+               int mt2_wlocked;
+#define mti_wlocked    mt2.mt2_wlocked
 #else
                pthread_mutex_t mt2_wmutex;
 #define mti_wmutex     mt2.mt2_wmutex
 #endif
                char pad[(MNAME_LEN+CACHELINE-1) & ~(CACHELINE-1)];
        } mt2;
-#endif
        MDB_reader      mti_readers[1];
 } MDB_txninfo;
 
@@ -719,7 +752,7 @@ typedef struct MDB_txninfo {
        ((uint32_t) \
         ((MDB_LOCK_VERSION) \
          /* Flags which describe functionality */ \
-         + (((MNAME_LEN) == 0)   << 18) /* MDB_USE_SYSV_SEM */ \
+         + (SYSV_SEM_FLAG << 18) \
          + (((MDB_PIDLOCK) != 0) << 16)))
 /** @} */
 
@@ -2596,17 +2629,8 @@ mdb_txn_renew0(MDB_txn *txn)
                if (ti) {
                        if (LOCK_MUTEX(rc, env, MDB_MUTEX(env, w)))
                                return rc;
-#ifdef MDB_USE_SYSV_SEM
-                       meta = env->me_metas[ mdb_env_pick_meta(env) ];
-                       txn->mt_txnid = meta->mm_txnid;
-                       /* Update mti_txnid like mdb_mutex_failed() would,
-                        * in case last writer crashed before updating it.
-                        */
-                       ti->mti_txnid = txn->mt_txnid;
-#else
                        txn->mt_txnid = ti->mti_txnid;
                        meta = env->me_metas[txn->mt_txnid & 1];
-#endif
                } else {
                        meta = env->me_metas[ mdb_env_pick_meta(env) ];
                        txn->mt_txnid = meta->mm_txnid;
@@ -4358,6 +4382,10 @@ mdb_env_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
        int fdflags;
 #      define MDB_CLOEXEC              0
 #endif
+#endif
+#ifdef MDB_USE_SYSV_SEM
+       int semid;
+       union semun semu;
 #endif
        int rc;
        off_t size, rsize;
@@ -4472,17 +4500,10 @@ mdb_env_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
                env->me_wmutex = CreateMutex(&mdb_all_sa, FALSE, env->me_txns->mti_wmname);
                if (!env->me_wmutex) goto fail_errno;
 #elif defined(MDB_USE_SYSV_SEM)
-               union semun semu;
                unsigned short vals[2] = {1, 1};
-               int semid = semget(IPC_PRIVATE, 2, mode);
+               semid = semget(IPC_PRIVATE, 2, mode);
                if (semid < 0)
                        goto fail_errno;
-
-               env->me_rmutex.semid = semid;
-               env->me_wmutex.semid = semid;
-               env->me_rmutex.semnum = 0;
-               env->me_wmutex.semnum = 1;
-
                semu.array = vals;
                if (semctl(semid, 0, SETALL, semu) < 0)
                        goto fail_errno;
@@ -4509,8 +4530,6 @@ mdb_env_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
        } else {
 #ifdef MDB_USE_SYSV_SEM
                struct semid_ds buf;
-               union semun semu;
-               int semid;
 #endif
                if (env->me_txns->mti_magic != MDB_MAGIC) {
                        DPUTS("lock region has invalid magic");
@@ -4535,20 +4554,23 @@ mdb_env_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
 #elif defined(MDB_USE_SYSV_SEM)
                semid = env->me_txns->mti_semid;
                semu.buf = &buf;
-
                /* check for read access */
                if (semctl(semid, 0, IPC_STAT, semu) < 0)
                        goto fail_errno;
                /* check for write access */
                if (semctl(semid, 0, IPC_SET, semu) < 0)
                        goto fail_errno;
-
-               env->me_rmutex.semid = semid;
-               env->me_wmutex.semid = semid;
-               env->me_rmutex.semnum = 0;
-               env->me_wmutex.semnum = 1;
 #endif
        }
+#ifdef MDB_USE_SYSV_SEM
+       env->me_rmutex.semid = semid;
+       env->me_wmutex.semid = semid;
+       env->me_rmutex.semnum = 0;
+       env->me_wmutex.semnum = 1;
+       env->me_rmutex.locked = &env->me_txns->mti_rlocked;
+       env->me_wmutex.locked = &env->me_txns->mti_wlocked;
+#endif
+
        return MDB_SUCCESS;
 
 fail_errno:
@@ -6140,7 +6162,6 @@ int
 mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
     unsigned int flags)
 {
-       enum { MDB_NO_ROOT = MDB_LAST_ERRCODE+10 }; /* internal code */
        MDB_env         *env;
        MDB_node        *leaf = NULL;
        MDB_page        *fp, *mp;
@@ -9593,7 +9614,7 @@ static int mdb_reader_check0(MDB_env *env, int rlocked, int *dead)
 
 #ifdef MDB_ROBUST_SUPPORTED
 /** Handle #LOCK_MUTEX0() failure.
- * With #MDB_ROBUST, try to repair the lock file if the mutex owner died.
+ * Try to repair the lock file if the mutex owner died.
  * @param[in] env      the environment handle
  * @param[in] mutex    LOCK_MUTEX0() mutex
  * @param[in] rc       LOCK_MUTEX0() error (nonzero)
@@ -9602,11 +9623,8 @@ static int mdb_reader_check0(MDB_env *env, int rlocked, int *dead)
 static int mdb_mutex_failed(MDB_env *env, mdb_mutex_t *mutex, int rc)
 {
        int toggle, rlocked, rc2;
-#ifndef _WIN32
-       enum { WAIT_ABANDONED = EOWNERDEAD };
-#endif
 
-       if (rc == (int) WAIT_ABANDONED) {
+       if (rc == MDB_OWNERDEAD) {
                /* We own the mutex. Clean up after dead previous owner. */
                rc = MDB_SUCCESS;
                rlocked = (mutex == MDB_MUTEX(env, r));
@@ -9627,7 +9645,7 @@ static int mdb_mutex_failed(MDB_env *env, mdb_mutex_t *mutex, int rc)
                        (rc ? "this process' env is hosed" : "recovering")));
                rc2 = mdb_reader_check0(env, rlocked, NULL);
                if (rc2 == 0)
-                       rc2 = pthread_mutex_consistent(mutex);
+                       rc2 = mdb_mutex_consistent(mutex);
                if (rc || (rc = rc2)) {
                        DPRINTF(("LOCK_MUTEX recovery failed, %s", mdb_strerror(rc)));
                        UNLOCK_MUTEX(mutex);