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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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75
src/txn.c
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@@ -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;
}
timestamp = 0;
continue;
ERROR("bailout waiting for valid snapshot (%s)",
"meta-pages are too volatile");
rc = MDBX_PROBLEM;
goto read_failed;
}
rc = coherency_check_head(txn, head, &timestamp);
/* Snap the state from current meta-head */
rc = coherency_fetch_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;
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);