114 lines
4.7 KiB
C
114 lines
4.7 KiB
C
/****************************************************************
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* *
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* Copyright 2009, 2010 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 "gdsbt.h"
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#include "gdsblk.h"
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#include "gdsfhead.h"
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#include "filestruct.h"
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#include "interlock.h"
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#include "sleep_cnt.h"
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#include "mupip_exit.h"
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#include "copy.h"
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#include "memcoherency.h"
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#include "add_inter.h"
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#include "shmpool.h"
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#include "db_snapshot.h"
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#define COMPUTE_BLOCK_OFFSET(blk, word, bit) \
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{ \
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word = blk / BLKS_PER_WORD; \
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bit = blk % BLKS_PER_WORD; \
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}
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boolean_t ss_chk_shdw_bitmap(sgmnt_addrs *csa, snapshot_context_ptr_t lcl_ss_ctx, block_id blk)
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{
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int word, bit;
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unsigned int *bitmap_addr;
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unsigned int concerned_word;
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node_local_ptr_t cnl;
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assert(NULL != lcl_ss_ctx);
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cnl = csa->nl;
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if (blk >= lcl_ss_ctx->total_blks)
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return FALSE;
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/* This function will be called by either GT.M while operating on phase 2 of the commit or by the snapshot initiator
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* ss_release (the function that invalidates a snapshot) waits for the existing phase 2 commits to complete and
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* the snapshot initiator will not call ss_release until it's done with it's operation. Hence the below assert is
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* safe to be used
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*/
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assert((SNAPSHOTS_IN_PROG(csa) || SNAPSHOTS_IN_PROG(cnl)));
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bitmap_addr = (unsigned int *)(lcl_ss_ctx->bitmap_addr); /* Point to the beginning of the shadow bitmap */
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/* It is possible that ss_chk_shdw_bitmap was called in the beginning of t_end or tp_tend where the snapshot context
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* information cannot be relied upon always as we don't hold crit when we copy information from snapshot information in
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* shared memory to the private snapshot context. So, the bitmap_addr value could be NULL in which case we don't want
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* to proceed as dereferencing would cause SIG11. Assert accordingly. */
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if (NULL == bitmap_addr)
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{
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assert(!csa->wcs_pidcnt_incremented);
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return FALSE;
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}
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COMPUTE_BLOCK_OFFSET(blk, word, bit);
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assert(0 == ((long)bitmap_addr % 4));
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/* MUPIP INTEG when running with -ONLINE uses the following approach:
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* 1. Checks if the shared memory has the bit turned ON for the block it's currently reading
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* 2. If TRUE, then read the block from the shadow temporary file
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* 3. If STEP 1 is FALSE, then read the block from the database file
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* 4. Check if this bit in the shared memory for this block is still turned OFF (as it was in STEP 1)
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* 5. If TRUE, proceed with the database block that was read in STEP 3
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* 6. If STEP 5 is FALSE (means the bit is now turned ON), discard the database block and read
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* from shadow temporary file
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* If not memory barrier is issued below, then an out-of-sync MUPIP INTEG process (running on a processor whose cache
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* is not in sync with other processes) might end up using the database block which is a post-update copy. So,
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* issue a READ memory barrier here to receive the changes done by other processors.
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*/
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SHM_READ_MEMORY_BARRIER;
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concerned_word = (*(unsigned int *)(bitmap_addr + word));
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if (concerned_word & (1 << bit))
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return TRUE;
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else
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return FALSE;
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}
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void ss_set_shdw_bitmap(sgmnt_addrs *csa, snapshot_context_ptr_t lcl_ss_ctx, block_id blk)
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{
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unsigned int *bitmap_addr;
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DEBUG_ONLY(unsigned int prev_val;)
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int word, bit;
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node_local_ptr_t cnl;
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shm_snapshot_ptr_t ss_shm_ptr;
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assert(NULL != lcl_ss_ctx);
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cnl = csa->nl;
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ss_shm_ptr = lcl_ss_ctx->ss_shm_ptr;
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DBG_ENSURE_PTR_WITHIN_SS_BOUNDS(csa, (sm_uc_ptr_t)ss_shm_ptr);
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assert(blk < lcl_ss_ctx->total_blks);
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/* This function will be called by GT.M while operating on phase 2 of the commit. ss_release (the function that
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* invalidates a snapshot) waits for the existing phase 2 commits to complete and Hence the below assert is safe to
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* be used
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*/
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assert(SNAPSHOTS_IN_PROG(csa) && ss_shm_ptr->in_use);
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/* Before dereferencing the shared memory, verify if the shared memory that GT.M has attached to and the one that
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* INTEG has created is actually in sync
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*/
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assert(lcl_ss_ctx->attach_shmid == cnl->ss_shmid);
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assert(ss_shm_ptr->ss_info.ss_shmid == lcl_ss_ctx->attach_shmid);
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bitmap_addr = (unsigned int *)(lcl_ss_ctx->bitmap_addr); /* Point to the beginning of the shadow bitmap */
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COMPUTE_BLOCK_OFFSET(blk, word, bit);
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DEBUG_ONLY(prev_val = (*(unsigned int *)(bitmap_addr + word));)
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assert(0 == (prev_val & (1 << bit)));
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INTERLOCK_ADD((bitmap_addr + word), &ss_shm_ptr->bitmap_latch, (1 << bit));
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return;
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}
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