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ITS#7969 LMDB: volatile & __synchronize().

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Globally shared fields of meta-data are not 'volatile'.
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leo@yuriev.ru 2014-10-17 22:22:39 +00:00 committed by Howard Chu
parent 925e7805a5
commit 9a80a8a8e8
1 changed files with 10 additions and 6 deletions
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16
libraries/liblmdb/mdb.c
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@ -610,11 +610,11 @@ typedef struct MDB_rxbody {
* started from so we can avoid overwriting any data used in that
* particular version.
*/
txnid_t mrb_txnid;
volatile txnid_t mrb_txnid;
/** The process ID of the process owning this reader txn. */
MDB_PID_T mrb_pid;
volatile MDB_PID_T mrb_pid;
/** The thread ID of the thread owning this txn. */
MDB_THR_T mrb_tid;
volatile MDB_THR_T mrb_tid;
} MDB_rxbody;
/** The actual reader record, with cacheline padding. */
@ -664,12 +664,12 @@ typedef struct MDB_txbody {
* This is recorded here only for convenience; the value can always
* be determined by reading the main database meta pages.
*/
txnid_t mtb_txnid;
volatile txnid_t mtb_txnid;
/** The number of slots that have been used in the reader table.
* This always records the maximum count, it is not decremented
* when readers release their slots.
*/
unsigned mtb_numreaders;
volatile unsigned mtb_numreaders;
} MDB_txbody;
/** The actual reader table definition. */
@ -942,7 +942,7 @@ typedef struct MDB_meta {
/** Any persistent environment flags. @ref mdb_env */
#define mm_flags mm_dbs[0].md_flags
pgno_t mm_last_pg; /**< last used page in file */
txnid_t mm_txnid; /**< txnid that committed this page */
volatile txnid_t mm_txnid; /**< txnid that committed this page */
} MDB_meta;
/** Buffer for a stack-allocated meta page.
@ -3601,6 +3601,10 @@ mdb_env_write_meta(MDB_txn *txn)
mp->mm_dbs[0] = txn->mt_dbs[0];
mp->mm_dbs[1] = txn->mt_dbs[1];
mp->mm_last_pg = txn->mt_next_pgno - 1;
#if !(defined(_MSC_VER) || defined(__i386__) || defined(__x86_64__))
/* LY: issue a memory barrier, if not x86. ITS#7969 */
__sync_synchronize();
#endif
mp->mm_txnid = txn->mt_txnid;
if (!(env->me_flags & (MDB_NOMETASYNC|MDB_NOSYNC))) {
unsigned meta_size = env->me_psize;