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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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7
src/lck-windows.c
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@@ -260,6 +260,7 @@ static int suspend_and_append(mdbx_handle_array_t **array,
MDBX_INTERNAL_FUNC int
mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array) {
mdbx_assert(env, (env->me_flags & MDBX_NOTLS) == 0);
const uintptr_t CurrentTid = GetCurrentThreadId();
int rc;
if (env->me_lck_mmap.lck) {
@@ -277,12 +278,6 @@ mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array) {
if (reader->mr_tid.weak == CurrentTid ||
reader->mr_tid.weak == WriteTxnOwner)
goto skip_lck;
if (env->me_flags & MDBX_NOTLS) {
/* Skip duplicates in no-tls mode */
for (const MDBX_reader *scan = reader; --scan >= begin;)
if (scan->mr_tid.weak == reader->mr_tid.weak)
goto skip_lck;
}
rc = suspend_and_append(array, (mdbx_tid_t)reader->mr_tid.weak);
if (rc != MDBX_SUCCESS) {