pps_fetch: introduce a helper to handle timeouts

[dragonfly.git] / sys / vfs / hammer2 / hammer2_cluster.c

/*
 * Copyright (c) 2013-2018 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@dragonflybsd.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * The cluster module collects multiple chains representing the same
 * information from different nodes into a single entity.  It allows direct
 * access to media data as long as it is not blockref array data (which
 * will obviously have to be different at each node).
 *
 * This module also handles I/O dispatch, status rollup, and various
 * mastership arrangements including quorum operations.  It effectively
 * presents one topology to the vnops layer.
 *
 * Many of the API calls mimic chain API calls but operate on clusters
 * instead of chains.  Please see hammer2_chain.c for more complete code
 * documentation of the API functions.
 *
 * WARNING! This module is *extremely* complex.  It must issue asynchronous
 *          locks and I/O, do quorum and/or master-slave processing, and
 *          it must operate properly even if some nodes are broken (which
 *          can also mean indefinite locks).
 *
 *                              CLUSTER OPERATIONS
 *
 * Cluster operations can be broken down into three pieces:
 *
 * (1) Chain locking and data retrieval.
 *
 *      - Most complex functions, quorum management on transaction ids.
 *
 *      - Locking and data accesses must be internally asynchronous.
 *
 *      - Validate and manage cache coherency primitives (cache state
 *        is stored in chain topologies but must be validated by these
 *        functions).
 *
 * (2) Lookups and Scans
 *              hammer2_cluster_lookup()
 *              hammer2_cluster_next()
 *
 *      - Depend on locking & data retrieval functions, but still complex.
 *
 *      - Must do quorum management on transaction ids.
 *
 *      - Lookup and Iteration ops Must be internally asynchronous.
 *
 * (3) Modifying Operations
 *              hammer2_cluster_create()
 *
 *      - Can usually punt on failures, operation continues unless quorum
 *        is lost.  If quorum is lost, must wait for resynchronization
 *        (depending on the management mode).
 *
 *      - Must disconnect node on failures (also not flush), remount, and
 *        resynchronize.
 *
 *      - Network links (via kdmsg) are relatively easy to issue as the
 *        complex underworkings of hammer2_chain.c don't have to messed
 *        with (the protocol is at a higher level than block-level).
 *
 *      - Multiple local disk nodes (i.e. block devices) are another matter.
 *        Chain operations have to be dispatched to per-node threads (xN)
 *        because we can't asynchronize potentially very complex chain
 *        operations in hammer2_chain.c (it would be a huge mess).
 *
 *        (these threads are also used to terminate incoming kdmsg ops from
 *        other machines).
 *
 *      - Single-node filesystems do not use threads and will simply call
 *        hammer2_chain.c functions directly.  This short-cut is handled
 *        at the base of each cluster function.
 */
#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/types.h>

#include "hammer2.h"

/*
 * Returns the bref type of the cluster's foucs.
 *
 * If the cluster is errored, returns HAMMER2_BREF_TYPE_EMPTY (0).
 * The cluster must be locked.
 */
uint8_t
hammer2_cluster_type(hammer2_cluster_t *cluster)
{
        if (cluster->error == 0) {
                KKASSERT(cluster->focus != NULL);
                return(cluster->focus->bref.type);
        }
        return 0;
}

/*
 * Returns the bref of the cluster's focus, sans any data-offset information
 * (since offset information is per-node and wouldn't be useful).
 *
 * Callers use this function to access modify_tid, mirror_tid, type,
 * key, and keybits.
 *
 * If the cluster is errored, returns an empty bref.
 * The cluster must be locked.
 */
void
hammer2_cluster_bref(hammer2_cluster_t *cluster, hammer2_blockref_t *bref)
{
        if (cluster->error == 0) {
                KKASSERT(cluster->focus != NULL);
                *bref = cluster->focus->bref;
                bref->data_off = 0;
        } else {
                bzero(bref, sizeof(*bref));
        }
}

/*
 * Create a degenerate cluster with one ref from a single locked chain.
 * The returned cluster will be focused on the chain and inherit its
 * error state.
 *
 * The chain's lock and reference are transfered to the new cluster, so
 * the caller should not try to unlock the chain separately.
 *
 * We fake the flags.
 */
void
hammer2_dummy_xop_from_chain(hammer2_xop_head_t *xop, hammer2_chain_t *chain)
{
        hammer2_cluster_t *cluster;

        bzero(xop, sizeof(*xop));

        cluster = &xop->cluster;
        cluster->array[0].chain = chain;
        cluster->array[0].flags = HAMMER2_CITEM_FEMOD;
        cluster->nchains = 1;
        cluster->focus = chain;
        cluster->focus_index = 0;
        cluster->pmp = chain->pmp;
        cluster->refs = 1;
        cluster->error = chain->error;
        cluster->flags = HAMMER2_CLUSTER_LOCKED |
                         HAMMER2_CLUSTER_WRHARD |
                         HAMMER2_CLUSTER_RDHARD |
                         HAMMER2_CLUSTER_MSYNCED |
                         HAMMER2_CLUSTER_SSYNCED;
}

/*
 * Add a reference to a cluster and its underlying chains.
 *
 * We must also ref the underlying chains in order to allow ref/unlock
 * sequences to later re-lock.
 */
void
hammer2_cluster_ref(hammer2_cluster_t *cluster)
{
        atomic_add_int(&cluster->refs, 1);
}

/*
 * Drop the caller's reference to the cluster.  When the ref count drops to
 * zero this function frees the cluster and drops all underlying chains.
 *
 * In-progress read I/Os are typically detached from the cluster once the
 * first one returns (the remaining stay attached to the DIOs but are then
 * ignored and drop naturally).
 */
void
hammer2_cluster_drop(hammer2_cluster_t *cluster)
{
        hammer2_chain_t *chain;
        int i;

        KKASSERT(cluster->refs > 0);
        if (atomic_fetchadd_int(&cluster->refs, -1) == 1) {
                cluster->focus = NULL;          /* safety XXX chg to assert */
                cluster->focus_index = 0;

                for (i = 0; i < cluster->nchains; ++i) {
                        chain = cluster->array[i].chain;
                        if (chain) {
                                hammer2_chain_drop(chain);
                                cluster->array[i].chain = NULL; /* safety */
                        }
                }
                cluster->nchains = 0;                           /* safety */

                kfree(cluster, M_HAMMER2);
                /* cluster is invalid */
        }
}

/*
 * Lock a cluster.  Cluster must already be referenced.  Focus is maintained.
 *
 * WARNING! This function expects the caller to handle resolution of the
 *          cluster.  We never re-resolve the cluster in this function,
 *          because it might be used to temporarily unlock/relock a cparent
 *          in an iteration or recursrion, and the cparents elements do not
 *          necessarily match.
 */
void
hammer2_cluster_lock(hammer2_cluster_t *cluster, int how)
{
        hammer2_chain_t *chain;
        int i;

        /* cannot be on inode-embedded cluster template, must be on copy */
        KKASSERT(cluster->refs > 0);
        KKASSERT((cluster->flags & HAMMER2_CLUSTER_INODE) == 0);
        if (cluster->flags & HAMMER2_CLUSTER_LOCKED) {
                panic("hammer2_cluster_lock: cluster %p already locked!\n",
                        cluster);
        }
        atomic_set_int(&cluster->flags, HAMMER2_CLUSTER_LOCKED);

        /*
         * Lock chains and resolve state.
         */
        for (i = 0; i < cluster->nchains; ++i) {
                chain = cluster->array[i].chain;
                if (chain == NULL)
                        continue;
                hammer2_chain_lock(chain, how);
        }
}

void
hammer2_cluster_unhold(hammer2_cluster_t *cluster)
{
        hammer2_chain_t *chain;
        int i;

        for (i = 0; i < cluster->nchains; ++i) {
                chain = cluster->array[i].chain;
                if (chain == NULL)
                        continue;
                hammer2_chain_unhold(chain);
        }
}

void
hammer2_cluster_rehold(hammer2_cluster_t *cluster)
{
        hammer2_chain_t *chain;
        int i;

        for (i = 0; i < cluster->nchains; ++i) {
                chain = cluster->array[i].chain;
                if (chain == NULL)
                        continue;
                hammer2_chain_rehold(chain);
        }
}

/*
 * This is used by the XOPS subsystem to calculate the state of
 * the collection and tell hammer2_xop_collect() what to do with it.
 * The collection can be in various states of desynchronization, the
 * caller specifically wants to resolve the passed-in key.
 *
 * Return values (HAMMER2_ERROR_*):
 *
 *      0               - Quorum agreement, key is valid
 *
 *      ENOENT          - Quorum agreement, end of scan
 *
 *      ESRCH           - Quorum agreement, key is INVALID (caller should
 *                        skip key).
 *
 *      EIO             - Quorum agreement but all elements had errors.
 *
 *      EDEADLK         - No quorum agreement possible for key, a repair
 *                        may be needed.  Caller has to decide what to do,
 *                        possibly iterating the key or generating an EIO.
 *
 *      EINPROGRESS     - No quorum agreement yet, but agreement is still
 *                        possible if caller waits for more responses.  Caller
 *                        should not iterate key.
 *
 *      CHECK           - CRC check error
 *
 * NOTE! If the pmp is in HMNT2_LOCAL mode, the cluster check always succeeds.
 *
 * XXX needs to handle SOFT_MASTER and SOFT_SLAVE
 */
int
hammer2_cluster_check(hammer2_cluster_t *cluster, hammer2_key_t key, int flags)
{
        hammer2_chain_t *chain;
        hammer2_chain_t *focus;
        hammer2_pfs_t *pmp;
        hammer2_tid_t quorum_tid;
        hammer2_tid_t last_best_quorum_tid;
        uint32_t nflags;
        int ttlmasters;
        int ttlslaves;
        int nmasters;
        int nmasters_keymatch;
        int nslaves;
        int nquorum;
        int umasters;   /* unknown masters (still in progress) */
        int error;
        int i;

        cluster->error = 0;
        cluster->focus = NULL;

        pmp = cluster->pmp;
        KKASSERT(pmp != NULL || cluster->nchains == 0);

        /*
         * Calculate quorum
         */
        nquorum = pmp ? pmp->pfs_nmasters / 2 + 1 : 0;
        nflags = 0;
        ttlmasters = 0;
        ttlslaves = 0;

        /*
         * Pass 1
         *
         * NOTE: A NULL chain is not necessarily an error, it could be
         *       e.g. a lookup failure or the end of an iteration.
         *       Process normally.
         */
        for (i = 0; i < cluster->nchains; ++i) {
                cluster->array[i].flags &= ~HAMMER2_CITEM_FEMOD;
                cluster->array[i].flags |= HAMMER2_CITEM_INVALID;

                chain = cluster->array[i].chain;
                error = cluster->array[i].error;
                if (chain && error) {
                        if (cluster->focus == NULL || cluster->focus == chain) {
                                /* error will be overridden by valid focus */
                                /* XXX */
                        }

                        /*
                         * Must count total masters and slaves whether the
                         * chain is errored or not.
                         */
                        switch (cluster->pmp->pfs_types[i]) {
                        case HAMMER2_PFSTYPE_SUPROOT:
                        case HAMMER2_PFSTYPE_MASTER:
                                ++ttlmasters;
                                break;
                        case HAMMER2_PFSTYPE_SLAVE:
                                ++ttlslaves;
                                break;
                        }
                        continue;
                }
                switch (cluster->pmp->pfs_types[i]) {
                case HAMMER2_PFSTYPE_MASTER:
                        ++ttlmasters;
                        break;
                case HAMMER2_PFSTYPE_SLAVE:
                        ++ttlslaves;
                        break;
                case HAMMER2_PFSTYPE_SOFT_MASTER:
                        nflags |= HAMMER2_CLUSTER_WRSOFT;
                        nflags |= HAMMER2_CLUSTER_RDSOFT;
                        break;
                case HAMMER2_PFSTYPE_SOFT_SLAVE:
                        nflags |= HAMMER2_CLUSTER_RDSOFT;
                        break;
                case HAMMER2_PFSTYPE_SUPROOT:
                        /*
                         * Degenerate cluster representing the super-root
                         * topology on a single device.  Fake stuff so
                         * cluster ops work as expected.
                         */
                        ++ttlmasters;
                        nflags |= HAMMER2_CLUSTER_WRHARD;
                        nflags |= HAMMER2_CLUSTER_RDHARD;
                        cluster->focus_index = i;
                        cluster->focus = chain;
                        cluster->error = error;
                        break;
                default:
                        break;
                }
        }

        /*
         * Pass 2
         *
         * Resolve nmasters             - master nodes fully match
         *
         * Resolve umasters             - master nodes operation still
         *                                in progress
         *
         * Resolve nmasters_keymatch    - master nodes match the passed-in
         *                                key and may or may not match
         *                                the quorum-agreed tid.
         *
         * The quorum-agreed TID is the highest matching TID.
         */
        last_best_quorum_tid = HAMMER2_TID_MAX;
        umasters = 0;
        nmasters = 0;
        nmasters_keymatch = 0;
        quorum_tid = 0;         /* fix gcc warning */

        while (nmasters < nquorum && last_best_quorum_tid != 0) {
                umasters = 0;
                nmasters = 0;
                nmasters_keymatch = 0;
                quorum_tid = 0;

                for (i = 0; i < cluster->nchains; ++i) {
                        /* XXX SOFT smpresent handling */
                        switch(cluster->pmp->pfs_types[i]) {
                        case HAMMER2_PFSTYPE_MASTER:
                        case HAMMER2_PFSTYPE_SUPROOT:
                                break;
                        default:
                                continue;
                        }

                        chain = cluster->array[i].chain;
                        error = cluster->array[i].error;

                        /*
                         * Skip elements still in progress.  umasters keeps
                         * track of masters that might still be in-progress.
                         */
                        if (chain == NULL && (cluster->array[i].flags &
                                              HAMMER2_CITEM_NULL) == 0) {
                                ++umasters;
                                continue;
                        }

                        /*
                         * Key match?
                         */
                        if (flags & HAMMER2_CHECK_NULL) {
                                if (chain == NULL) {
                                        ++nmasters;
                                        ++nmasters_keymatch;
                                        if (cluster->error == 0)
                                                cluster->error = error;
                                }
                        } else if (chain &&
                                   (key == (hammer2_key_t)-1 ||
                                    chain->bref.key == key)) {
                                ++nmasters_keymatch;

                                if (chain->bref.modify_tid <
                                     last_best_quorum_tid &&
                                    quorum_tid < chain->bref.modify_tid) {
                                        /*
                                         * Select new TID as master if better
                                         * than any found so far in this loop,
                                         * as long as it does not reach the
                                         * best tid found in the previous loop.
                                         */
                                        nmasters = 0;
                                        quorum_tid = chain->bref.modify_tid;
                                }
                                if (quorum_tid == chain->bref.modify_tid) {
                                        /*
                                         * TID matches current collection.
                                         *
                                         * (error handled in next pass)
                                         */
                                        ++nmasters;
                                        if (chain->error == 0) {
                                                cluster->focus = chain;
                                                cluster->focus_index = i;
                                        }
                                }
                        }
                }
                if (nmasters >= nquorum)
                        break;
                last_best_quorum_tid = quorum_tid;
        }

        /*
        kprintf("nmasters %d/%d nmaster_keymatch=%d umasters=%d\n",
                nmasters, nquorum, nmasters_keymatch, umasters);
        */

        /*
         * Early return if we do not have enough masters.
         */
        if (nmasters < nquorum) {
                if (nmasters + umasters >= nquorum)
                        return HAMMER2_ERROR_EINPROGRESS;
                if (nmasters_keymatch < nquorum)
                        return HAMMER2_ERROR_ESRCH;
                return HAMMER2_ERROR_EDEADLK;
        }

        /*
         * Validated end of scan.
         */
        if (flags & HAMMER2_CHECK_NULL) {
                if (cluster->error == 0)
                        cluster->error = HAMMER2_ERROR_ENOENT;
                return cluster->error;
        }

        /*
         * If we have a NULL focus at this point the agreeing quorum all
         * had chain errors.
         */
        if (cluster->focus == NULL)
                return HAMMER2_ERROR_EIO;

        /*
         * Pass 3
         *
         * We have quorum agreement, validate elements, not end of scan.
         */
        nslaves = 0;
        cluster->error = 0;

        for (i = 0; i < cluster->nchains; ++i) {
                chain = cluster->array[i].chain;
                error = cluster->array[i].error;
                if (chain == NULL ||
                    chain->bref.key != key ||
                    chain->bref.modify_tid != quorum_tid) {
                        continue;
                }

                /*
                 * Quorum Match
                 *
                 * XXX for now, cumulative error.
                 */
                if (cluster->error == 0)
                        cluster->error = error;

                switch (cluster->pmp->pfs_types[i]) {
                case HAMMER2_PFSTYPE_MASTER:
                        cluster->array[i].flags |= HAMMER2_CITEM_FEMOD;
                        cluster->array[i].flags &= ~HAMMER2_CITEM_INVALID;
                        nflags |= HAMMER2_CLUSTER_WRHARD;
                        nflags |= HAMMER2_CLUSTER_RDHARD;
                        break;
                case HAMMER2_PFSTYPE_SLAVE:
                        /*
                         * We must have enough up-to-date masters to reach
                         * a quorum and the slave modify_tid must match the
                         * quorum's modify_tid.
                         *
                         * Do not select an errored slave.
                         */
                        cluster->array[i].flags &= ~HAMMER2_CITEM_INVALID;
                        nflags |= HAMMER2_CLUSTER_RDHARD;
                        ++nslaves;
                        break;
                case HAMMER2_PFSTYPE_SOFT_MASTER:
                        /*
                         * Directly mounted soft master always wins.  There
                         * should be only one.
                         */
                        cluster->array[i].flags |= HAMMER2_CITEM_FEMOD;
                        cluster->array[i].flags &= ~HAMMER2_CITEM_INVALID;
                        break;
                case HAMMER2_PFSTYPE_SOFT_SLAVE:
                        /*
                         * Directly mounted soft slave always wins.  There
                         * should be only one.
                         *
                         * XXX
                         */
                        cluster->array[i].flags &= ~HAMMER2_CITEM_INVALID;
                        break;
                case HAMMER2_PFSTYPE_SUPROOT:
                        /*
                         * spmp (degenerate case)
                         */
                        cluster->array[i].flags |= HAMMER2_CITEM_FEMOD;
                        cluster->array[i].flags &= ~HAMMER2_CITEM_INVALID;
                        nflags |= HAMMER2_CLUSTER_WRHARD;
                        nflags |= HAMMER2_CLUSTER_RDHARD;
                        break;
                default:
                        break;
                }
        }

        /*
         * Focus now set, adjust ddflag.  Skip this pass if the focus
         * is bad or if we are at the PFS root (the bref won't match at
         * the PFS root, obviously).
         *
         * focus is probably not locked and it isn't safe to test its
         * content (e.g. focus->data, focus->dio, other content).  We
         * do not synchronize the dio to the cpu here.  In fact, in numerous
         * situations the frontend doesn't even need to access its dio/data,
         * so synchronizing it here would be wasteful.
         */
        focus = cluster->focus;
        if (focus) {
                cluster->ddflag =
                        (cluster->focus->bref.type == HAMMER2_BREF_TYPE_INODE);
        } else {
                cluster->ddflag = 0;
                goto skip4;
        }
        if (cluster->focus->flags & HAMMER2_CHAIN_PFSBOUNDARY)
                goto skip4;

        /*
         * Pass 4
         *
         * Validate the elements that were not marked invalid.  They should
         * match.
         */
        for (i = 0; i < cluster->nchains; ++i) {
                int ddflag;

                chain = cluster->array[i].chain;

                if (chain == NULL)
                        continue;
                if (chain == focus)
                        continue;
                if (cluster->array[i].flags & HAMMER2_CITEM_INVALID)
                        continue;

                ddflag = (chain->bref.type == HAMMER2_BREF_TYPE_INODE);
                if (chain->bref.type != focus->bref.type ||
                    chain->bref.key != focus->bref.key ||
                    chain->bref.keybits != focus->bref.keybits ||
                    chain->bref.modify_tid != focus->bref.modify_tid ||
                    chain->bytes != focus->bytes ||
                    ddflag != cluster->ddflag) {
                        cluster->array[i].flags |= HAMMER2_CITEM_INVALID;
                        if (hammer2_debug & 1)
                        kprintf("cluster_check: matching modify_tid failed "
                                "bref test: idx=%d type=%02x/%02x "
                                "key=%016jx/%d-%016jx/%d "
                                "mod=%016jx/%016jx bytes=%u/%u\n",
                                i,
                                chain->bref.type, focus->bref.type,
                                chain->bref.key, chain->bref.keybits,
                                focus->bref.key, focus->bref.keybits,
                                chain->bref.modify_tid, focus->bref.modify_tid,
                                chain->bytes, focus->bytes);
                        if (hammer2_debug & 0x4000)
                                panic("cluster_check");
                        /* flag issue and force resync? */
                }
        }
skip4:

        if (ttlslaves == 0)
                nflags |= HAMMER2_CLUSTER_NOSOFT;
        if (ttlmasters == 0)
                nflags |= HAMMER2_CLUSTER_NOHARD;

        /*
         * Set SSYNCED or MSYNCED for slaves and masters respectively if
         * all available nodes (even if 0 are available) are fully
         * synchronized.  This is used by the synchronization thread to
         * determine if there is work it could potentially accomplish.
         */
        if (nslaves == ttlslaves)
                nflags |= HAMMER2_CLUSTER_SSYNCED;
        if (nmasters == ttlmasters)
                nflags |= HAMMER2_CLUSTER_MSYNCED;

        /*
         * Determine if the cluster was successfully locked for the
         * requested operation and generate an error code.  The cluster
         * will not be locked (or ref'd) if an error is returned.
         */
        atomic_set_int(&cluster->flags, nflags);
        atomic_clear_int(&cluster->flags, HAMMER2_CLUSTER_ZFLAGS & ~nflags);

        return cluster->error;
}

/*
 * Unlock a cluster.  Refcount and focus is maintained.
 */
void
hammer2_cluster_unlock(hammer2_cluster_t *cluster)
{
        hammer2_chain_t *chain;
        int i;

        if ((cluster->flags & HAMMER2_CLUSTER_LOCKED) == 0) {
                kprintf("hammer2_cluster_unlock: cluster %p not locked\n",
                        cluster);
        }
        KKASSERT(cluster->flags & HAMMER2_CLUSTER_LOCKED);
        KKASSERT(cluster->refs > 0);
        atomic_clear_int(&cluster->flags, HAMMER2_CLUSTER_LOCKED);

        for (i = 0; i < cluster->nchains; ++i) {
                chain = cluster->array[i].chain;
                if (chain)
                        hammer2_chain_unlock(chain);
        }
}