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mdbx: исправление и рефакторинг цикла чтения мета-страниц при старте читающих транзакций.

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Сценарий достаточно запутанный/сложный.
This commit is contained in:
Леонид Юрьев (Leonid Yuriev) 2024-08-11 00:00:22 +03:00
parent aca692212f
commit b054a69e72
4 changed files with 51 additions and 38 deletions
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2
src/api-env.c
View File

@ -1274,7 +1274,7 @@ __cold int mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower,
uint64_t timestamp = 0;
while ("workaround for "
"https://libmdbx.dqdkfa.ru/dead-github/issues/269") {
rc = coherency_check_head(env->basal_txn, head, &timestamp);
rc = coherency_fetch_head(env->basal_txn, head, &timestamp);
if (likely(rc == MDBX_SUCCESS))
break;
if (unlikely(rc != MDBX_RESULT_TRUE))

10
src/coherency.c
View File

@ -152,18 +152,20 @@ __cold int coherency_timeout(uint64_t *timestamp, intptr_t pgno,
/* check with timeout as the workaround
* for https://libmdbx.dqdkfa.ru/dead-github/issues/269 */
__hot int coherency_check_head(MDBX_txn *txn, const meta_ptr_t head,
__hot int coherency_fetch_head(MDBX_txn *txn, const meta_ptr_t head,
uint64_t *timestamp) {
/* Copy the DB info and flags */
txn->geo = head.ptr_v->geometry;
txn->txnid = head.txnid;
txn->geo = head.ptr_c->geometry;
memcpy(txn->dbs, &head.ptr_c->trees, sizeof(head.ptr_c->trees));
STATIC_ASSERT(sizeof(head.ptr_c->trees) == CORE_DBS * sizeof(tree_t));
VALGRIND_MAKE_MEM_UNDEFINED(txn->dbs + CORE_DBS,
txn->env->max_dbi - CORE_DBS);
txn->canary = head.ptr_v->canary;
txn->canary = head.ptr_c->canary;
if (unlikely(!coherency_check(txn->env, head.txnid, txn->dbs, head.ptr_v,
*timestamp == 0)))
*timestamp == 0) ||
txn->txnid != meta_txnid(head.ptr_v)))
return coherency_timeout(timestamp, -1, txn->env);
if (unlikely(txn->dbs[FREE_DBI].flags != MDBX_INTEGERKEY)) {

2
src/proto.h
View File

@ -113,7 +113,7 @@ MDBX_INTERNAL int __must_check_result tbl_setup(const MDBX_env *env,
MDBX_INTERNAL bool coherency_check_meta(const MDBX_env *env,
const volatile meta_t *meta,
bool report);
MDBX_INTERNAL int coherency_check_head(MDBX_txn *txn, const meta_ptr_t head,
MDBX_INTERNAL int coherency_fetch_head(MDBX_txn *txn, const meta_ptr_t head,
uint64_t *timestamp);
MDBX_INTERNAL int coherency_check_written(const MDBX_env *env,
const txnid_t txnid,

77
src/txn.c
View File

@ -982,7 +982,7 @@ int txn_renew(MDBX_txn *txn, unsigned flags) {
likely(env->stuck_meta < 0)
? /* regular */ meta_recent(env, &troika)
: /* recovery mode */ meta_ptr(env, env->stuck_meta);
if (likely(r)) {
if (likely(r != nullptr)) {
safe64_reset(&r->txnid, true);
atomic_store32(&r->snapshot_pages_used,
head.ptr_v->geometry.first_unallocated, mo_Relaxed);
@ -1005,46 +1005,57 @@ int txn_renew(MDBX_txn *txn, unsigned flags) {
}
jitter4testing(true);
/* Snap the state from current meta-head */
txn->txnid = head.txnid;
if (likely(env->stuck_meta < 0) &&
unlikely(meta_should_retry(env, &troika) ||
head.txnid < atomic_load64(&env->lck->cached_oldest,
mo_AcquireRelease))) {
if (unlikely(++loop > 42)) {
ERROR("bailout waiting for valid snapshot (%s)",
"metapages are too volatile");
rc = MDBX_PROBLEM;
txn->txnid = INVALID_TXNID;
if (likely(r))
safe64_reset(&r->txnid, true);
goto bailout;
}
if (unlikely(meta_should_retry(env, &troika))) {
retry:
if (likely(++loop < 42)) {
timestamp = 0;
continue;
}
rc = coherency_check_head(txn, head, &timestamp);
jitter4testing(false);
if (likely(rc == MDBX_SUCCESS))
break;
if (unlikely(rc != MDBX_RESULT_TRUE)) {
txn->txnid = INVALID_TXNID;
if (likely(r))
safe64_reset(&r->txnid, true);
goto bailout;
ERROR("bailout waiting for valid snapshot (%s)",
"meta-pages are too volatile");
rc = MDBX_PROBLEM;
goto read_failed;
}
/* Snap the state from current meta-head */
rc = coherency_fetch_head(txn, head, &timestamp);
jitter4testing(false);
if (unlikely(rc != MDBX_SUCCESS)) {
if (rc == MDBX_RESULT_TRUE)
goto retry;
else
goto read_failed;
}
const uint64_t snap_oldest =
atomic_load64(&env->lck->cached_oldest, mo_AcquireRelease);
if (unlikely(txn->txnid < snap_oldest)) {
if (env->stuck_meta < 0)
goto retry;
ERROR("target meta-page %i is referenced to an obsolete MVCC-snapshot "
"%" PRIaTXN " < cached-oldest %" PRIaTXN,
env->stuck_meta, txn->txnid, snap_oldest);
rc = MDBX_MVCC_RETARDED;
goto read_failed;
}
if (likely(r != nullptr) &&
unlikely(txn->txnid != atomic_load64(&r->txnid, mo_Relaxed)))
goto retry;
break;
}
if (unlikely(txn->txnid < MIN_TXNID || txn->txnid > MAX_TXNID)) {
ERROR("%s", "environment corrupted by died writer, must shutdown!");
if (likely(r))
safe64_reset(&r->txnid, true);
txn->txnid = INVALID_TXNID;
rc = MDBX_CORRUPTED;
read_failed:
txn->txnid = INVALID_TXNID;
if (likely(r != nullptr))
safe64_reset(&r->txnid, true);
goto bailout;
}
tASSERT(txn, rc == MDBX_SUCCESS);
ENSURE(env,
txn->txnid >=
/* paranoia is appropriate here */ env->lck->cached_oldest.weak);
@ -1092,14 +1103,14 @@ int txn_renew(MDBX_txn *txn, unsigned flags) {
const meta_ptr_t head = meta_recent(env, &txn->tw.troika);
uint64_t timestamp = 0;
while ("workaround for https://libmdbx.dqdkfa.ru/dead-github/issues/269") {
rc = coherency_check_head(txn, head, &timestamp);
rc = coherency_fetch_head(txn, head, &timestamp);
if (likely(rc == MDBX_SUCCESS))
break;
if (unlikely(rc != MDBX_RESULT_TRUE))
goto bailout;
}
eASSERT(env, meta_txnid(head.ptr_v) == head.txnid);
txn->txnid = safe64_txnid_next(head.txnid);
eASSERT(env, meta_txnid(head.ptr_v) == txn->txnid);
txn->txnid = safe64_txnid_next(txn->txnid);
if (unlikely(txn->txnid > MAX_TXNID)) {
rc = MDBX_TXN_FULL;
ERROR("txnid overflow, raise %d", rc);