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Overlay for serializing modifications of a specific entry without
using backend-specific locks
This commit is contained in:
Howard Chu
parent
c8f49d0337
commit
59b50101bd
1 changed files with 202 additions and 0 deletions
202
servers/slapd/overlays/seqmod.c
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202
servers/slapd/overlays/seqmod.c
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/* seqmod.c - sequenced modifies */
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/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
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*
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* Copyright 2004 The OpenLDAP Foundation.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted only as authorized by the OpenLDAP
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* Public License.
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*
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* A copy of this license is available in the file LICENSE in the
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* top-level directory of the distribution or, alternatively, at
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* <http://www.OpenLDAP.org/license.html>.
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*/
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/* ACKNOWLEDGEMENTS:
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* This work was initially developed by Howard Chu for inclusion in
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* OpenLDAP Software.
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*/
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#include "portable.h"
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#define SLAPD_OVER_SEQMOD SLAPD_MOD_STATIC
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#ifdef SLAPD_OVER_SEQMOD
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#include "slap.h"
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/* This overlay serializes concurrent attempts to modify a single entry */
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typedef struct modtarget {
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struct modtarget *mt_next;
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struct modtarget *mt_tail;
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Operation *mt_op;
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} modtarget;
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typedef struct seqmod_info {
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Avlnode *sm_mods; /* entries being modified */
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ldap_pvt_thread_mutex_t sm_mutex;
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} seqmod_info;
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static int
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sm_avl_cmp( const void *c1, const void *c2 )
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{
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const modtarget *m1, *m2;
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int rc;
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m1 = c1; m2 = c2;
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rc = m1->mt_op->o_req_ndn.bv_len - m2->mt_op->o_req_ndn.bv_len;
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if ( rc ) return rc;
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return ber_bvcmp( &m1->mt_op->o_req_ndn, &m2->mt_op->o_req_ndn );
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}
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static int
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seqmod_op_cleanup( Operation *op, SlapReply *rs )
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{
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seqmod_info *sm = op->o_callback->sc_private;
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modtarget *mt;
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Avlnode *av;
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/* This op is done, remove it */
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ldap_pvt_thread_mutex_lock( &sm->sm_mutex );
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av = avl_find( sm->sm_mods, mt, sm_avl_cmp );
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assert(av);
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mt = av->avl_data;
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/* If there are more, promote the next one */
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if ( mt->mt_next ) {
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av->avl_data = mt->mt_next;
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mt->mt_next->mt_tail = mt->mt_tail;
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} else {
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avl_delete( &sm->sm_mods, mt, sm_avl_cmp );
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}
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ldap_pvt_thread_mutex_unlock( &sm->sm_mutex );
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op->o_callback = op->o_callback->sc_next;
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op->o_tmpfree( op->o_callback, op->o_tmpmemctx );
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return 0;
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}
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static int
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seqmod_op_mod( Operation *op, SlapReply *rs )
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{
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slap_overinst *on = (slap_overinst *)op->o_bd->bd_info;
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seqmod_info *sm = on->on_bi.bi_private;
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modtarget *mt;
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Avlnode *av;
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slap_callback *cb;
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cb = op->o_tmpcalloc( 1, sizeof(slap_callback) + sizeof(modtarget),
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op->o_tmpmemctx );
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mt = (modtarget *)(cb+1);
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mt->mt_next = NULL;
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mt->mt_tail = mt;
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mt->mt_op = op;
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/* See if we're already modifying this entry - don't allow
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* near-simultaneous mods of the same entry
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*/
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ldap_pvt_thread_mutex_lock( &sm->sm_mutex );
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av = avl_find( sm->sm_mods, mt, sm_avl_cmp );
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if ( av ) {
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modtarget *mtp = av->avl_data;
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mtp->mt_tail->mt_next = mt;
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mtp->mt_tail = mt;
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/* Wait for this op to get to head of list */
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while ( mtp != mt ) {
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ldap_pvt_thread_mutex_unlock( &sm->sm_mutex );
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ldap_pvt_thread_yield();
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/* Let it finish - should use a condition
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* variable here... */
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ldap_pvt_thread_mutex_lock( &sm->sm_mutex );
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mtp = av->avl_data;
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}
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} else {
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/* Record that we're modifying this now */
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avl_insert( &sm->sm_mods, mt, sm_avl_cmp, avl_dup_error );
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}
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ldap_pvt_thread_mutex_unlock( &sm->sm_mutex );
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cb->sc_cleanup = seqmod_op_cleanup;
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cb->sc_private = sm;
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cb->sc_next = op->o_callback;
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op->o_callback = cb;
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return SLAP_CB_CONTINUE;
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}
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static int
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seqmod_op_extended(
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Operation *op,
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SlapReply *rs
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)
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{
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if ( exop_is_write( op )) return seqmod_op_mod( op, rs );
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else return SLAP_CB_CONTINUE;
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}
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static int
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seqmod_db_open(
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BackendDB *be
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)
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{
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slap_overinst *on = (slap_overinst *)be->bd_info;
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seqmod_info *sm;
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sm = ch_calloc(1, sizeof(seqmod_info));
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on->on_bi.bi_private = sm;
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ldap_pvt_thread_mutex_init( &sm->sm_mutex );
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return 0;
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}
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static int
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seqmod_db_close(
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BackendDB *be
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)
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{
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slap_overinst *on = (slap_overinst *)be->bd_info;
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seqmod_info *sm = (seqmod_info *)on->on_bi.bi_private;
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if ( sm ) {
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ldap_pvt_thread_mutex_destroy( &sm->sm_mutex );
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ch_free( sm );
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}
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return 0;
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}
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/* This overlay is set up for dynamic loading via moduleload. For static
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* configuration, you'll need to arrange for the slap_overinst to be
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* initialized and registered by some other function inside slapd.
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*/
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static slap_overinst seqmod;
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int
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seqmod_init()
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{
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seqmod.on_bi.bi_type = "seqmod";
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seqmod.on_bi.bi_db_open = seqmod_db_open;
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seqmod.on_bi.bi_db_close = seqmod_db_close;
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seqmod.on_bi.bi_op_modify = seqmod_op_mod;
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seqmod.on_bi.bi_op_modrdn = seqmod_op_mod;
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seqmod.on_bi.bi_extended = seqmod_op_extended;
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return overlay_register( &seqmod );
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}
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#if SLAPD_OVER_SEQMOD == SLAPD_MOD_DYNAMIC
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int
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init_module( int argc, char *argv[] )
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{
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return seqmod_init();
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}
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#endif /* SLAPD_OVER_SEQMOD == SLAPD_MOD_DYNAMIC */
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#endif /* defined(SLAPD_OVER_SEQMOD) */
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