leo@yuriev.ru wrote:

The attached files is derived from OpenLDAP Software. All of the modifications to OpenLDAP Software represented in the following patch(es) were developed by Peter-Service LLC, Moscow, Russia. Peter-Service LLC has not assigned rights and/or interest in this work to any party. I, Leonid Yuriev am authorized by Peter-Service LLC, my employer, to release this work under the following terms.

Peter-Service LLC hereby places the following modifications to OpenLDAP Software (and only these modifications) into the public domain. Hence, these modifications may be freely used and/or redistributed for any purpose with or without attribution and/or other notice.

Committed to mdb.master. The whitespace is wrong in all of the patches you submitted, had to apply them manually.

commit 5e83ea8a76f81dac8d5a9dcd74d5b10a01330102 Author: Leo Yuriev leo@yuriev.ru Date: 2014-09-12 01:32:13 +0400

 ITS#7969 for LMDB: volatile & __synchronize().

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c index 6cc3433..3286ffb 100644 --- a/libraries/liblmdb/mdb.c +++ b/libraries/liblmdb/mdb.c @@ -580,11 +580,11 @@ 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. */

@@ -632,12 +632,12 @@ 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. */

@@ -908,7 +908,7 @@ 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.

@@ -3559,6 +3559,10 @@ 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. */
• __sync_synchronize();

+#endif mp->mm_txnid = txn->mt_txnid; if (!(env->me_flags & (MDB_NOMETASYNC|MDB_NOSYNC))) { unsigned meta_size = env->me_psize;