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mdbx: fix meta-invalidate race in MDBX_WRITEMAP mode (when target == head).

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This commit is contained in:
Leo Yuriev 2017-05-26 15:44:00 +03:00
parent f4d3b76f81
commit 4293840055
1 changed files with 36 additions and 14 deletions
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50
src/mdbx.c
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@ -3508,27 +3508,49 @@ static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
const size_t offset = (char *)target - env->me_map;
mdbx_assert(env, ((env->me_flags ^ flags) & MDBX_WRITEMAP) == 0);
mdbx_ensure(env, target == head || target->mm_txnid < pending->mm_txnid);
if (env->me_flags & MDBX_WRITEMAP) {
/* LY: 'invalidate' the meta. */
mdbx_jitter4testing(true);
if (target->mm_datasync_sign != MDBX_DATASIGN_WEAK ||
target->mm_txnid != pending->mm_txnid) {
if (likely(target != head)) {
#ifdef NDEBUG
/* nodebug: 'invalidate' the meta to avoid false-reading
* from violators (make safer) */
target->mm_datasync_sign = MDBX_DATASIGN_WEAK;
mdbx_jitter4testing(true);
target->mm_txnid = 0;
mdbx_coherent_barrier();
#else
/* debug: provoke failure to catch a violators */
memset(target->mm_dbs, 0xCC,
sizeof(target->mm_dbs) + sizeof(target->mm_canary));
mdbx_jitter4testing(false);
#endif
/* LY: update info */
target->mm_mapsize = pending->mm_mapsize;
target->mm_dbs[FREE_DBI] = pending->mm_dbs[FREE_DBI];
target->mm_dbs[MAIN_DBI] = pending->mm_dbs[MAIN_DBI];
target->mm_canary = pending->mm_canary;
target->mm_last_pg = pending->mm_last_pg;
mdbx_jitter4testing(true);
mdbx_coherent_barrier();
/* LY: 'commit' the meta */
target->mm_txnid = pending->mm_txnid;
mdbx_jitter4testing(true);
} else {
/* dangerous case (target == head), only mm_datasync_sign could
* me updated, check assertions once again */
mdbx_ensure(env, head->mm_txnid == pending->mm_txnid &&
!META_IS_STEADY(head) && META_IS_STEADY(pending));
mdbx_ensure(env, head->mm_last_pg == pending->mm_last_pg);
mdbx_ensure(env, head->mm_mapsize == pending->mm_mapsize);
mdbx_ensure(env, memcmp(&head->mm_dbs, &pending->mm_dbs,
sizeof(head->mm_dbs)) == 0);
mdbx_ensure(env, memcmp(&head->mm_canary, &pending->mm_canary,
sizeof(head->mm_canary)) == 0);
}
/* LY: update info */
target->mm_mapsize = pending->mm_mapsize;
target->mm_dbs[FREE_DBI] = pending->mm_dbs[FREE_DBI];
target->mm_dbs[MAIN_DBI] = pending->mm_dbs[MAIN_DBI];
target->mm_last_pg = pending->mm_last_pg;
target->mm_canary = pending->mm_canary;
/* LY: 'commit' the meta */
mdbx_jitter4testing(true);
target->mm_txnid = pending->mm_txnid;
mdbx_jitter4testing(true);
target->mm_datasync_sign = pending->mm_datasync_sign;
mdbx_coherent_barrier();
mdbx_jitter4testing(true);
} else {
pending->mm_magic = MDBX_MAGIC;