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mdbx: reduces number of getpid() calls for checking PID against fork().

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PID check could be ommited:
 - on Linux when madvise(MADV_DONTFORK) is available. i.e. after the fork()
    mapped pages will not be available for child process.
 - in Windows where fork() not available.

Change-Id: I4dd6bcb209cfc816ae3ec43825ea913d2249663c
This commit is contained in:
Leonid Yuriev 2019-07-16 11:52:10 +03:00
parent 7c7d5f4434
commit 0b8ac37450
2 changed files with 25 additions and 0 deletions
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13
src/bits.h
View File

@ -1213,3 +1213,16 @@ static __inline void mdbx_jitter4testing(bool tiny) {
(void)tiny;
#endif
}
/* Controls checking PID against reuse DB environment after the fork() */
#ifndef MDBX_TXN_CHECKPID
#if defined(MADV_DONTFORK) || defined(_WIN32) || defined(_WIN64)
/* PID check could be ommited:
* - on Linux when madvise(MADV_DONTFORK) is available. i.e. after the fork()
* mapped pages will not be available for child process.
* - in Windows where fork() not available. */
#define MDBX_TXN_CHECKPID 0
#else
#define MDBX_TXN_CHECKPID 1
#endif
#endif /* MDBX_TXN_CHECKPID */

12
src/mdbx.c
View File

@ -3155,10 +3155,12 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) {
MDBX_env *env = txn->mt_env;
int rc;
#if MDBX_TXN_CHECKPID
if (unlikely(env->me_pid != mdbx_getpid())) {
env->me_flags |= MDBX_FATAL_ERROR;
return MDBX_PANIC;
}
#endif /* MDBX_TXN_CHECKPID */
STATIC_ASSERT(sizeof(MDBX_reader) == MDBX_CACHELINE_SIZE);
STATIC_ASSERT(offsetof(MDBX_lockinfo, mti_numreaders) % MDBX_CACHELINE_SIZE ==
@ -3436,8 +3438,10 @@ int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags,
if (unlikely(env->me_signature != MDBX_ME_SIGNATURE))
return MDBX_EBADSIGN;
#if MDBX_TXN_CHECKPID
if (unlikely(env->me_pid != mdbx_getpid()))
env->me_flags |= MDBX_FATAL_ERROR;
#endif /* MDBX_TXN_CHECKPID */
if (unlikely(env->me_flags & MDBX_FATAL_ERROR))
return MDBX_PANIC;
@ -3635,10 +3639,12 @@ static int mdbx_txn_end(MDBX_txn *txn, unsigned mode) {
MDBX_env *env = txn->mt_env;
static const char *const names[] = MDBX_END_NAMES;
#if MDBX_TXN_CHECKPID
if (unlikely(txn->mt_env->me_pid != mdbx_getpid())) {
env->me_flags |= MDBX_FATAL_ERROR;
return MDBX_PANIC;
}
#endif /* MDBX_TXN_CHECKPID */
mdbx_debug("%s txn %" PRIaTXN "%c %p on mdbenv %p, root page %" PRIaPGNO
"/%" PRIaPGNO,
@ -4719,10 +4725,12 @@ int mdbx_txn_commit(MDBX_txn *txn) {
return MDBX_THREAD_MISMATCH;
MDBX_env *env = txn->mt_env;
#if MDBX_TXN_CHECKPID
if (unlikely(env->me_pid != mdbx_getpid())) {
env->me_flags |= MDBX_FATAL_ERROR;
return MDBX_PANIC;
}
#endif /* MDBX_TXN_CHECKPID */
if (txn->mt_child) {
rc = mdbx_txn_commit(txn->mt_child);
@ -5716,8 +5724,10 @@ mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower, intptr_t size_now,
if (unlikely(env->me_signature != MDBX_ME_SIGNATURE))
return MDBX_EBADSIGN;
#if MDBX_TXN_CHECKPID
if (unlikely(env->me_pid != mdbx_getpid()))
env->me_flags |= MDBX_FATAL_ERROR;
#endif /* MDBX_TXN_CHECKPID */
if (unlikely(env->me_flags & MDBX_FATAL_ERROR))
return MDBX_PANIC;
@ -12636,10 +12646,12 @@ int __cold mdbx_reader_check(MDBX_env *env, int *dead) {
int __cold mdbx_reader_check0(MDBX_env *env, int rdt_locked, int *dead) {
mdbx_assert(env, rdt_locked >= 0);
#if MDBX_TXN_CHECKPID
if (unlikely(env->me_pid != mdbx_getpid())) {
env->me_flags |= MDBX_FATAL_ERROR;
return MDBX_PANIC;
}
#endif /* MDBX_TXN_CHECKPID */
MDBX_lockinfo *const lck = env->me_lck;
if (unlikely(lck == NULL)) {