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mdbx: fix/refine mdbx_find_largest().

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Change-Id: Ib40ca0014da18793be0bdae5133806304ad42819
This commit is contained in:
Leonid Yuriev 2019-07-09 02:46:24 +03:00
parent 421f4b01e6
commit 4ecf78163d
1 changed files with 11 additions and 4 deletions
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15
src/mdbx.c
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@ -2207,12 +2207,19 @@ static pgno_t mdbx_find_largest(MDBX_env *env, pgno_t largest) {
if (likely(lck != NULL /* exclusive mode */)) {
const unsigned snap_nreaders = lck->mti_numreaders;
for (unsigned i = 0; i < snap_nreaders; ++i) {
retry:
if (lck->mti_readers[i].mr_pid) {
/* mdbx_jitter4testing(true); */
const pgno_t snap = lck->mti_readers[i].mr_snapshot_pages;
if (snap && snap >= largest &&
lck->mti_oldest >= lck->mti_readers[i].mr_txnid)
largest = snap;
const pgno_t snap_pages = lck->mti_readers[i].mr_snapshot_pages;
const txnid_t snap_txnid = lck->mti_readers[i].mr_txnid;
mdbx_memory_barrier();
if (unlikely(snap_pages != lck->mti_readers[i].mr_snapshot_pages ||
snap_txnid != lck->mti_readers[i].mr_txnid))
goto retry;
if (largest < snap_pages &&
lck->mti_oldest <= /* ignore pending updates */ snap_txnid &&
snap_txnid <= env->me_txn0->mt_txnid)
largest = snap_pages;
}
}
}