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mdbx: avoid tran-trap in mdb_txn_renew0() by mt_flags.

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Avoid read txn-flags from shared write TXN (e.g. env->me_tnx0->mt_flags)
without holding a write-mutex.

Change-Id: I3a3a64597f69b7df205043c567a51fe509247826
This commit is contained in:
Leo Yuriev 2015-12-04 22:06:30 +03:00
parent 6069149b05
commit 50c480e2de
1 changed files with 10 additions and 11 deletions
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21
mdb.c
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@ -2700,11 +2700,11 @@ mdb_reader_pid(MDB_env *env, int op, pid_t pid)
* @return 0 on success, non-zero on failure. * @return 0 on success, non-zero on failure.
*/ */
static int static int
mdb_txn_renew0(MDB_txn *txn) mdb_txn_renew0(MDB_txn *txn, unsigned flags)
{ {
MDB_env *env = txn->mt_env; MDB_env *env = txn->mt_env;
MDB_meta *meta; MDB_meta *meta;
unsigned i, nr, flags = txn->mt_flags; unsigned i, nr;
uint16_t x; uint16_t x;
int rc, new_notls = 0; int rc, new_notls = 0;
@ -2713,9 +2713,11 @@ mdb_txn_renew0(MDB_txn *txn)
return MDB_PANIC; return MDB_PANIC;
} }
if ((flags &= MDB_TXN_RDONLY) != 0) { if (flags & MDB_TXN_RDONLY) {
struct MDB_rthc *rthc = NULL; struct MDB_rthc *rthc = NULL;
MDB_reader *r = NULL; MDB_reader *r = NULL;
txn->mt_flags = MDB_TXN_RDONLY;
if (likely(env->me_flags & MDB_ENV_TXKEY)) { if (likely(env->me_flags & MDB_ENV_TXKEY)) {
mdb_assert(env, !(env->me_flags & MDB_NOTLS)); mdb_assert(env, !(env->me_flags & MDB_NOTLS));
rthc = pthread_getspecific(env->me_txkey); rthc = pthread_getspecific(env->me_txkey);
@ -2811,9 +2813,9 @@ mdb_txn_renew0(MDB_txn *txn)
return rc; return rc;
meta = mdb_meta_head_w(env); meta = mdb_meta_head_w(env);
txn->mt_txnid = meta->mm_txnid; txn->mt_txnid = meta->mm_txnid + 1;
txn->mt_flags = flags;
txn->mt_txnid++;
#if MDB_DEBUG #if MDB_DEBUG
if (unlikely(txn->mt_txnid == mdb_debug_edge)) { if (unlikely(txn->mt_txnid == mdb_debug_edge)) {
if (! mdb_debug_logger) if (! mdb_debug_logger)
@ -2842,8 +2844,6 @@ mdb_txn_renew0(MDB_txn *txn)
txn->mt_next_pgno = meta->mm_last_pg+1; txn->mt_next_pgno = meta->mm_last_pg+1;
} }
txn->mt_flags = flags;
/* Setup db info */ /* Setup db info */
txn->mt_numdbs = env->me_numdbs; txn->mt_numdbs = env->me_numdbs;
for (i=CORE_DBS; i<txn->mt_numdbs; i++) { for (i=CORE_DBS; i<txn->mt_numdbs; i++) {
@ -2880,7 +2880,7 @@ mdb_txn_renew(MDB_txn *txn)
if (unlikely(!F_ISSET(txn->mt_flags, MDB_TXN_RDONLY|MDB_TXN_FINISHED))) if (unlikely(!F_ISSET(txn->mt_flags, MDB_TXN_RDONLY|MDB_TXN_FINISHED)))
return EINVAL; return EINVAL;
rc = mdb_txn_renew0(txn); rc = mdb_txn_renew0(txn, MDB_TXN_RDONLY);
if (rc == MDB_SUCCESS) { if (rc == MDB_SUCCESS) {
mdb_debug("renew txn %zu%c %p on mdbenv %p, root page %zu", mdb_debug("renew txn %zu%c %p on mdbenv %p, root page %zu",
txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w', txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w',
@ -2988,13 +2988,12 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned flags, MDB_txn **ret)
} else { /* MDB_RDONLY */ } else { /* MDB_RDONLY */
txn->mt_dbiseqs = env->me_dbiseqs; txn->mt_dbiseqs = env->me_dbiseqs;
renew: renew:
rc = mdb_txn_renew0(txn); rc = mdb_txn_renew0(txn, flags);
} }
if (unlikely(rc)) { if (unlikely(rc)) {
if (txn != env->me_txn0) if (txn != env->me_txn0)
free(txn); free(txn);
} else { } else {
txn->mt_flags |= flags; /* could not change txn=me_txn0 earlier */
txn->mt_signature = MDBX_MT_SIGNATURE; txn->mt_signature = MDBX_MT_SIGNATURE;
*ret = txn; *ret = txn;
mdb_debug("begin txn %zu%c %p on mdbenv %p, root page %zu", mdb_debug("begin txn %zu%c %p on mdbenv %p, root page %zu",
@ -9306,7 +9305,7 @@ mdb_env_copyfd0(MDB_env *env, HANDLE fd)
if (unlikely(rc)) if (unlikely(rc))
goto leave; goto leave;
rc = mdb_txn_renew0(txn); rc = mdb_txn_renew0(txn, MDB_RDONLY);
if (rc) { if (rc) {
mdb_mutex_unlock(env, wmutex); mdb_mutex_unlock(env, wmutex);
goto leave; goto leave;