109 lines
3.8 KiB
C
109 lines
3.8 KiB
C
/****************************************************************
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* *
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* Copyright 2001, 2011 Fidelity Information Services, Inc *
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* *
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* This source code contains the intellectual property *
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* of its copyright holder(s), and is made available *
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* under a license. If you do not know the terms of *
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* the license, please stop and do not read further. *
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* *
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****************************************************************/
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#include "mdef.h"
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#include "gdsroot.h"
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#include "gtm_facility.h"
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#include "fileinfo.h"
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#include "gdsbt.h"
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#include "gdsfhead.h"
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#include "gdsbgtr.h"
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#include "cache.h"
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#include "hashtab.h" /* needed for cws_insert.h */
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#include "hashtab_int4.h" /* needed for cws_insert.h */
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#include "longset.h" /* needed for cws_insert.h */
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#include "cws_insert.h"
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GBLREF sgmnt_addrs *cs_addrs;
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GBLREF unsigned int t_tries;
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GBLREF boolean_t mu_reorg_process;
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#define ENOUGH_TRIES_TO_FALL_BACK 17
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/* This function returns a pointer to the cache_rec entry, NULL if not found, or CR_INVALID if the hash table is corrupt */
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cache_rec_ptr_t db_csh_get(block_id block) /* block number to look up */
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{
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register sgmnt_addrs *csa;
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sgmnt_data_ptr_t csd;
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cache_rec_ptr_t cr, cr_hash_base;
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int blk_hash, lcnt, ocnt, hmax;
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bool is_mm;
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# ifdef DEBUG
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cache_rec_ptr_t cr_low, cr_high;
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# endif
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csa = cs_addrs;
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csd = csa->hdr;
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is_mm = (dba_mm == csd->acc_meth);
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assert((FALSE == is_mm) || (csa->now_crit)); /* if MM you should be in crit */
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VMS_ONLY(assert(FALSE == is_mm);) /* in VMS, MM should never call db_csh_get */
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hmax = csd->bt_buckets;
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blk_hash = (block % hmax);
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if (!is_mm)
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{
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DEBUG_ONLY(cr_low = &csa->acc_meth.bg.cache_state->cache_array[0];)
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DEBUG_ONLY(cr_high = cr_low + csd->bt_buckets + csd->n_bts;)
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cr_hash_base = csa->acc_meth.bg.cache_state->cache_array + blk_hash;
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} else
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{
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DEBUG_ONLY(cr_low = (cache_rec_ptr_t)(csa->acc_meth.mm.mmblk_state->mmblk_array);)
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DEBUG_ONLY(cr_high = (cache_rec_ptr_t)(csa->acc_meth.mm.mmblk_state->mmblk_array + csd->bt_buckets + csd->n_bts);)
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cr_hash_base = (cache_rec_ptr_t)(csa->acc_meth.mm.mmblk_state->mmblk_array + blk_hash);
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}
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ocnt = 0;
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do
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{
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cr = cr_hash_base;
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assert((0 == cr->blk) || (BT_QUEHEAD == cr->blk));
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lcnt = hmax;
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do
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{
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cr = (cache_rec_ptr_t)((sm_uc_ptr_t)cr + cr->blkque.fl);
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assert(!CR_NOT_ALIGNED(cr, cr_low) && !CR_NOT_IN_RANGE(cr, cr_low, cr_high)
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UNIX_ONLY(|| is_mm));
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if (BT_QUEHEAD == cr->blk)
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{ /* We have reached the end of the queue, validate we have run the queue
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* back around to the same queue header or we'll need to retry because the
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* queue changed on us.
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*/
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if (cr == cr_hash_base)
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return (cache_rec_ptr_t)NULL;
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break; /* Retry - something changed */
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}
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if ((CR_BLKEMPTY != cr->blk) && ((cr->blk % hmax) != blk_hash))
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break; /* Retry - something changed */
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assert(!csa->now_crit || (0 != cr->blkque.fl) && (0 != cr->blkque.bl));
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if (cr->blk == block)
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{
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if (!is_mm)
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{
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if (CDB_STAGNATE <= t_tries || mu_reorg_process)
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CWS_INSERT(block);
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/* setting refer outside of crit may not prevent its replacement, but that's an
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* inefficiency, not a tragedy because of concurrency checks in t_end or tp_tend;
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* the real problem is to ensure that the cache_rec layout is such that this
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* assignment does not damage other fields.
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*/
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cr->refer = TRUE;
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}
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return cr;
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}
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lcnt--;
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} while (lcnt);
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ocnt++;
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/* We rarely expect to come here, hence it is considered better to recompute the maximum value of ocnt (for the
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* termination check) instead of storing it in a local variable at the beginning of the do loop */
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} while (ocnt < (csa->now_crit ? 1 : ENOUGH_TRIES_TO_FALL_BACK));
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BG_TRACE_PRO_ANY(csa, db_csh_get_too_many_loops);
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return (TRUE == csa->now_crit ? (cache_rec_ptr_t)CR_NOTVALID : (cache_rec_ptr_t) NULL);
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}
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