tdb2: check PID if we are holding a lock.
[ccan] / ccan / tdb2 / lock.c
index cad6480326897e27aa5d6c2e96a602ecc3a2b236..5b04c0d243d9b29f2a5104af3f7836a5a47e8f40 100644 (file)
@@ -37,6 +37,29 @@ static enum TDB_ERROR owner_conflict(struct tdb_context *tdb, const char *call)
                          call);
 }
 
+/* If we fork, we no longer really own locks. */
+static bool check_lock_pid(struct tdb_context *tdb,
+                          const char *call, bool log)
+{
+       /* No locks?  No problem! */
+       if (tdb->file->allrecord_lock.count == 0
+           && tdb->file->num_lockrecs == 0) {
+               return true;
+       }
+
+       /* No fork?  No problem! */
+       if (tdb->file->locker == getpid()) {
+               return true;
+       }
+
+       if (log) {
+               tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
+                          "%s: fork() detected after lock acquisition!"
+                          " (%u vs %u)", call, tdb->file->locker, getpid());
+       }
+       return false;
+}
+
 static int fcntl_lock(struct tdb_context *tdb,
                      int rw, off_t off, off_t len, bool waitflag)
 {
@@ -48,6 +71,11 @@ static int fcntl_lock(struct tdb_context *tdb,
        fl.l_len = len;
        fl.l_pid = 0;
 
+       if (tdb->file->allrecord_lock.count == 0
+           && tdb->file->num_lockrecs == 0) {
+               tdb->file->locker = getpid();
+       }
+
        add_stat(tdb, lock_lowlevel, 1);
        if (waitflag)
                return fcntl(tdb->file->fd, F_SETLKW, &fl);
@@ -190,7 +218,8 @@ static enum TDB_ERROR tdb_brunlock(struct tdb_context *tdb,
                ret = fcntl_unlock(tdb, rw_type, offset, len);
        } while (ret == -1 && errno == EINTR);
 
-       if (ret == -1) {
+       /* If we fail, *then* we verify that we owned the lock.  If not, ok. */
+       if (ret == -1 && check_lock_pid(tdb, "tdb_brunlock", false)) {
                return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
                                  "tdb_brunlock failed (fd=%d) at offset %zu"
                                  " rw_type=%d len=%zu",
@@ -210,6 +239,9 @@ enum TDB_ERROR tdb_allrecord_upgrade(struct tdb_context *tdb)
 {
        int count = 1000;
 
+       if (!check_lock_pid(tdb, "tdb_transaction_prepare_commit", true))
+               return TDB_ERR_LOCK;
+
        if (tdb->file->allrecord_lock.count != 1) {
                return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
                                  "tdb_allrecord_upgrade failed:"
@@ -267,6 +299,9 @@ enum TDB_ERROR tdb_lock_and_recover(struct tdb_context *tdb)
 {
        enum TDB_ERROR ecode;
 
+       if (!check_lock_pid(tdb, "tdb_transaction_prepare_commit", true))
+               return TDB_ERR_LOCK;
+
        ecode = tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK,
                                   false);
        if (ecode != TDB_SUCCESS) {
@@ -303,6 +338,10 @@ static enum TDB_ERROR tdb_nest_lock(struct tdb_context *tdb,
        if (tdb->flags & TDB_NOLOCK)
                return TDB_SUCCESS;
 
+       if (!check_lock_pid(tdb, "tdb_nest_lock", true)) {
+               return TDB_ERR_LOCK;
+       }
+
        add_stat(tdb, locks, 1);
 
        new_lck = find_nestlock(tdb, offset, NULL);
@@ -472,6 +511,13 @@ enum TDB_ERROR tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
        enum TDB_ERROR ecode;
        tdb_bool_err berr;
 
+       if (tdb->flags & TDB_NOLOCK)
+               return TDB_SUCCESS;
+
+       if (!check_lock_pid(tdb, "tdb_allrecord_lock", true)) {
+               return TDB_ERR_LOCK;
+       }
+
        if (tdb->file->allrecord_lock.count) {
                if (tdb->file->allrecord_lock.owner != tdb) {
                        return owner_conflict(tdb, "tdb_allrecord_lock");
@@ -587,6 +633,9 @@ void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
 /* unlock entire db */
 void tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
 {
+       if (tdb->flags & TDB_NOLOCK)
+               return;
+
        if (tdb->file->allrecord_lock.count == 0) {
                tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
                           "tdb_allrecord_unlock: not locked!");
@@ -664,6 +713,9 @@ enum TDB_ERROR tdb_lock_hashes(struct tdb_context *tdb,
 
        /* a allrecord lock allows us to avoid per chain locks */
        if (tdb->file->allrecord_lock.count) {
+               if (!check_lock_pid(tdb, "tdb_lock_hashes", true))
+                       return TDB_ERR_LOCK;
+
                if (tdb->file->allrecord_lock.owner != tdb)
                        return owner_conflict(tdb, "tdb_lock_hashes");
                if (ltype == tdb->file->allrecord_lock.ltype
@@ -736,6 +788,9 @@ enum TDB_ERROR tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
 
        /* a allrecord lock allows us to avoid per chain locks */
        if (tdb->file->allrecord_lock.count) {
+               if (!check_lock_pid(tdb, "tdb_lock_free_bucket", true))
+                       return TDB_ERR_LOCK;
+
                if (tdb->file->allrecord_lock.ltype == F_WRLCK)
                        return 0;
                return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,