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mdbx: partial fix for recursive SRW-lock with MDBX_NOTLS on Windows.

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Here are some changes to avoid recursive acquisition of SRW-lock,
which is still in use:
 - Read transactions don't acquire the shared SRW-lock with `MDBX_NOTLS.
 - Memory-mapping of DB is always kept while DB opened,
   therefore following limitations are:
 - DB file can't be shrinked while it used,
   including auto-shrink due to auto-compactification with corresponding geometry settings.
 - The upper limit of DB size can't be changed while DB is used.
 - The DB can grow within the upper size limit defined while opening by a first process,
   but this does not work under Wine since there is no `NtExtendSection()` function.

Partially fix https://github.com/erthink/libmdbx/issues/203
This commit is contained in:
Leonid Yuriev
2021-06-10 02:57:32 +03:00
parent 18bc28bea2
commit d7c06b1337
5 changed files with 125 additions and 95 deletions
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92
src/core.c
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@@ -5888,16 +5888,6 @@ static __cold int mdbx_set_readahead(MDBX_env *env, const pgno_t edge,
static __cold int mdbx_mapresize(MDBX_env *env, const pgno_t used_pgno,
const pgno_t size_pgno,
const pgno_t limit_pgno, const bool implicit) {
if ((env->me_flags & MDBX_WRITEMAP) && env->me_lck->mti_unsynced_pages.weak) {
#if MDBX_ENABLE_PGOP_STAT
safe64_inc(&env->me_lck->mti_pgop_stat.wops, 1);
#endif /* MDBX_ENABLE_PGOP_STAT */
int err = mdbx_msync(&env->me_dxb_mmap, 0,
pgno_align2os_bytes(env, used_pgno), MDBX_SYNC_NONE);
if (unlikely(err != MDBX_SUCCESS))
return err;
}
const size_t limit_bytes = pgno_align2os_bytes(env, limit_pgno);
const size_t size_bytes = pgno_align2os_bytes(env, size_pgno);
const size_t prev_size = env->me_dxb_mmap.current;
@@ -5915,6 +5905,8 @@ static __cold int mdbx_mapresize(MDBX_env *env, const pgno_t used_pgno,
mdbx_assert(env, bytes2pgno(env, size_bytes) >= size_pgno);
mdbx_assert(env, bytes2pgno(env, limit_bytes) >= limit_pgno);
unsigned mresize_flags =
env->me_flags & (MDBX_RDONLY | MDBX_WRITEMAP | MDBX_UTTERLY_NOSYNC);
#if defined(_WIN32) || defined(_WIN64)
/* Acquire guard in exclusive mode for:
* - to avoid collision between read and write txns around env->me_dbgeo;
@@ -5928,28 +5920,30 @@ static __cold int mdbx_mapresize(MDBX_env *env, const pgno_t used_pgno,
size_bytes == env->me_dxb_mmap.filesize)
goto bailout;
/* 1) Windows allows only extending a read-write section, but not a
* corresponding mapped view. Therefore in other cases we must suspend
* the local threads for safe remap.
* 2) At least on Windows 10 1803 the entire mapped section is unavailable
* for short time during NtExtendSection() or VirtualAlloc() execution.
* 3) Under Wine runtime environment on Linux a section extending is not
* supported. Therefore thread suspending is always required.
*
* THEREFORE LOCAL THREADS SUSPENDING IS ALWAYS REQUIRED! */
array_onstack.limit = ARRAY_LENGTH(array_onstack.handles);
array_onstack.count = 0;
suspended = &array_onstack;
rc = mdbx_suspend_threads_before_remap(env, &suspended);
if (rc != MDBX_SUCCESS) {
mdbx_error("failed suspend-for-remap: errcode %d", rc);
goto bailout;
if ((env->me_flags & MDBX_NOTLS) == 0) {
/* 1) Windows allows only extending a read-write section, but not a
* corresponding mapped view. Therefore in other cases we must suspend
* the local threads for safe remap.
* 2) At least on Windows 10 1803 the entire mapped section is unavailable
* for short time during NtExtendSection() or VirtualAlloc() execution.
* 3) Under Wine runtime environment on Linux a section extending is not
* supported.
*
* THEREFORE LOCAL THREADS SUSPENDING IS ALWAYS REQUIRED! */
array_onstack.limit = ARRAY_LENGTH(array_onstack.handles);
array_onstack.count = 0;
suspended = &array_onstack;
rc = mdbx_suspend_threads_before_remap(env, &suspended);
if (rc != MDBX_SUCCESS) {
mdbx_error("failed suspend-for-remap: errcode %d", rc);
goto bailout;
}
mresize_flags |= implicit ? MDBX_MRESIZE_MAY_UNMAP
: MDBX_MRESIZE_MAY_UNMAP | MDBX_MRESIZE_MAY_MOVE;
}
const bool mapping_can_be_moved = !implicit;
#else /* Windows */
#else /* Windows */
/* Acquire guard to avoid collision between read and write txns
* around env->me_dbgeo */
bool mapping_can_be_moved = false;
int rc = mdbx_fastmutex_acquire(&env->me_remap_guard);
if (unlikely(rc != MDBX_SUCCESS))
return rc;
@@ -5958,7 +5952,8 @@ static __cold int mdbx_mapresize(MDBX_env *env, const pgno_t used_pgno,
goto bailout;
MDBX_lockinfo *const lck = env->me_lck_mmap.lck;
if (limit_bytes != env->me_dxb_mmap.limit && lck && !implicit) {
if (limit_bytes != env->me_dxb_mmap.limit && !(env->me_flags & MDBX_NOTLS) &&
lck && !implicit) {
int err = mdbx_rdt_lock(env) /* lock readers table until remap done */;
if (unlikely(MDBX_IS_ERROR(err))) {
rc = err;
@@ -5968,21 +5963,31 @@ static __cold int mdbx_mapresize(MDBX_env *env, const pgno_t used_pgno,
/* looking for readers from this process */
const unsigned snap_nreaders =
atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
mapping_can_be_moved = true;
mresize_flags |= implicit ? MDBX_MRESIZE_MAY_UNMAP
: MDBX_MRESIZE_MAY_UNMAP | MDBX_MRESIZE_MAY_MOVE;
for (unsigned i = 0; i < snap_nreaders; ++i) {
if (lck->mti_readers[i].mr_pid.weak == env->me_pid &&
lck->mti_readers[i].mr_tid.weak != mdbx_thread_self()) {
/* the base address of the mapping can't be changed since
* the other reader thread from this process exists. */
mdbx_rdt_unlock(env);
mapping_can_be_moved = false;
mresize_flags &= ~(MDBX_MRESIZE_MAY_UNMAP | MDBX_MRESIZE_MAY_MOVE);
break;
}
}
}
#endif /* ! Windows */
if ((env->me_flags & MDBX_WRITEMAP) && env->me_lck->mti_unsynced_pages.weak) {
#if MDBX_ENABLE_PGOP_STAT
safe64_inc(&env->me_lck->mti_pgop_stat.wops, 1);
#endif /* MDBX_ENABLE_PGOP_STAT */
rc = mdbx_msync(&env->me_dxb_mmap, 0, pgno_align2os_bytes(env, used_pgno),
MDBX_SYNC_NONE);
if (unlikely(rc != MDBX_SUCCESS))
goto bailout;
}
#if MDBX_ENABLE_MADVISE
if (size_bytes < prev_size) {
mdbx_notice("resize-MADV_%s %u..%u",
@@ -6020,8 +6025,7 @@ static __cold int mdbx_mapresize(MDBX_env *env, const pgno_t used_pgno,
}
#endif /* MDBX_ENABLE_MADVISE */
rc = mdbx_mresize(env->me_flags, &env->me_dxb_mmap, size_bytes, limit_bytes,
mapping_can_be_moved);
rc = mdbx_mresize(mresize_flags, &env->me_dxb_mmap, size_bytes, limit_bytes);
#if MDBX_ENABLE_MADVISE
if (rc == MDBX_SUCCESS) {
@@ -6056,7 +6060,7 @@ bailout:
}
#endif /* MDBX_USE_VALGRIND */
} else {
if (rc != MDBX_UNABLE_EXTEND_MAPSIZE) {
if (rc != MDBX_UNABLE_EXTEND_MAPSIZE && rc != MDBX_RESULT_TRUE) {
mdbx_error("failed resize datafile/mapping: "
"present %" PRIuPTR " -> %" PRIuPTR ", "
"limit %" PRIuPTR " -> %" PRIuPTR ", errcode %d",
@@ -6084,7 +6088,8 @@ bailout:
mdbx_free(suspended);
}
#else
if (env->me_lck_mmap.lck && mapping_can_be_moved)
if (env->me_lck_mmap.lck &&
(mresize_flags & (MDBX_MRESIZE_MAY_UNMAP | MDBX_MRESIZE_MAY_MOVE)) != 0)
mdbx_rdt_unlock(env);
int err = mdbx_fastmutex_release(&env->me_remap_guard);
#endif /* Windows */
@@ -7629,12 +7634,13 @@ static int mdbx_txn_renew0(MDBX_txn *txn, const unsigned flags) {
}
if (txn->mt_flags & MDBX_TXN_RDONLY) {
#if defined(_WIN32) || defined(_WIN64)
if ((size > env->me_dbgeo.lower && env->me_dbgeo.shrink) ||
(mdbx_RunningUnderWine() &&
/* under Wine acquisition of remap_guard is always required,
* since Wine don't support section extending,
* i.e. in both cases unmap+map are required. */
size < env->me_dbgeo.upper && env->me_dbgeo.grow)) {
if (((size > env->me_dbgeo.lower && env->me_dbgeo.shrink) ||
(mdbx_RunningUnderWine() &&
/* under Wine acquisition of remap_guard is always required,
* since Wine don't support section extending,
* i.e. in both cases unmap+map are required. */
size < env->me_dbgeo.upper && env->me_dbgeo.grow)) &&
/* avoid recursive use SRW */ (txn->mt_flags & MDBX_NOTLS) == 0) {
txn->mt_flags |= MDBX_SHRINK_ALLOWED;
mdbx_srwlock_AcquireShared(&env->me_remap_guard);
}