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lmdb: ITS#7971 Fix reader allocation and me_numreaders.

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Change-Id: I75c8325de342c2a28592fb0c7a718f95855e7e4d
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Hallvard Furuseth 2015-01-17 06:32:12 +01:00 committed by Leo Yuriev
parent 62181cfe87
commit ae747bb4ce
1 changed files with 17 additions and 10 deletions
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27
mdb.c
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@ -1327,7 +1327,8 @@ struct MDB_env {
unsigned int me_psize; /**< DB page size, inited from me_os_psize */
unsigned int me_os_psize; /**< OS page size, from #GET_PAGESIZE */
unsigned int me_maxreaders; /**< size of the reader table */
unsigned int me_numreaders; /**< max numreaders set by this env */
/** Max #MDB_txninfo.%mti_numreaders of interest to #mdb_env_close() */
volatile int me_close_readers;
MDB_dbi me_numdbs; /**< number of DBs opened */
MDB_dbi me_maxdbs; /**< size of the DB table */
MDB_PID_T me_pid; /**< process ID of this env */
@ -2968,14 +2969,20 @@ mdb_txn_renew0(MDB_txn *txn)
return MDB_READERS_FULL;
}
r = &ti->mti_readers[i];
/* Claim the reader slot, carefully since other code
* uses the reader table un-mutexed: First reset the
* slot, next publish it in mti_numreaders. After
* that, it is safe for mdb_env_close() to touch it.
* When it will be closed, we can finally claim it.
*/
r->mr_pid = 0;
r->mr_txnid = (txnid_t)-1;
r->mr_tid = tid;
r->mr_pid = pid; /* should be written last, see ITS#7971. */
mdb_coherent_barrier();
if (i == nr)
ti->mti_numreaders = ++nr;
/* Save numreaders for un-mutexed mdb_env_close() */
env->me_numreaders = nr;
env->me_close_readers = nr;
r->mr_pid = pid;
UNLOCK_MUTEX(rmutex);
new_notls = (env->me_flags & MDB_NOTLS);
@ -5357,8 +5364,12 @@ mdb_env_close0(MDB_env *env, int excl)
MDB_PID_T pid = env->me_pid;
/* Clearing readers is done in this function because
* me_txkey with its destructor must be disabled first.
*
* We skip the the reader mutex, so we touch only
* data owned by this process (me_close_readers and
* our readers), and clear each reader atomically.
*/
for (i = env->me_numreaders; --i >= 0; )
for (i = env->me_close_readers; --i >= 0; )
if (env->me_txns->mti_readers[i].mr_pid == pid)
env->me_txns->mti_readers[i].mr_pid = 0;
#ifdef _WIN32
@ -9678,11 +9689,7 @@ mdb_env_info(MDB_env *env, MDB_envinfo *arg)
arg->me_mapaddr = env->me_metas[toggle]->mm_address;
arg->me_mapsize = env->me_mapsize;
arg->me_maxreaders = env->me_maxreaders;
/* me_numreaders may be zero if this process never used any readers. Use
* the shared numreader count if it exists.
*/
arg->me_numreaders = env->me_txns ? env->me_txns->mti_numreaders : env->me_numreaders;
arg->me_numreaders = env->me_txns ? env->me_txns->mti_numreaders : 0;
arg->me_last_pgno = env->me_metas[toggle]->mm_last_pg;
arg->me_last_txnid = env->me_metas[toggle]->mm_txnid;