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mdbx: refine lck-posix implementation.

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This commit is contained in:
Leonid Yuriev 2019-08-11 19:13:29 +03:00
parent 036144eed4
commit 69f831af0b
1 changed files with 19 additions and 21 deletions
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40
src/lck-posix.c
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@ -167,11 +167,16 @@ int __cold mdbx_lck_seize(MDBX_env *env) {
(env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK,
env->me_pid, 1);
if (rc == 0) {
/* got dxb-shared-rw */
return MDBX_RESULT_FALSE;
/* got dxb-shared, try lck-shared */
rc = mdbx_lck_op(env->me_lfd, OP_SETLKW, F_RDLCK, 0, 1);
if (rc == 0) {
/* got both dxb and lck shared lock */
return MDBX_RESULT_FALSE;
}
mdbx_error("%s(%s) failed: errcode %u", mdbx_func_, "lck-shared", rc);
} else {
mdbx_error("%s(%s) failed: errcode %u", mdbx_func_, "dxb-shared", rc);
}
mdbx_error("%s(%s) failed: errcode %u", mdbx_func_,
"lock-against-without-lck", rc);
assert(MDBX_IS_ERROR(rc));
}
@ -184,7 +189,9 @@ bailout:
int mdbx_lck_downgrade(MDBX_env *env, bool complete) {
assert(env->me_lfd != INVALID_HANDLE_VALUE);
int rc = mdbx_lck_op(env->me_lfd, OP_SETLK, F_UNLCK, 0, OFF_T_MAX);
int rc = mdbx_lck_op(env->me_lfd, OP_SETLK, F_UNLCK, 1, OFF_T_MAX - 1);
if (rc == 0)
rc = mdbx_lck_op(env->me_lfd, OP_SETLKW, F_RDLCK, 0, 1);
if (unlikely(rc != 0)) {
mdbx_error("%s(%s) failed: errcode %u", mdbx_func_, "lck", rc);
goto bailout;
@ -251,22 +258,13 @@ bailout:
}
void __cold mdbx_lck_destroy(MDBX_env *env) {
if (env->me_lfd != INVALID_HANDLE_VALUE && env->me_lck) {
/* try get exclusive access */
if (mdbx_lck_op(env->me_fd, OP_SETLK,
(env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK, 0,
OFF_T_MAX) == 0 &&
mdbx_lck_op(env->me_lfd, OP_SETLKW, F_WRLCK, 0, OFF_T_MAX) == 0) {
mdbx_info("%s: got exclusive, drown mutexes", mdbx_func_);
int rc = pthread_mutex_destroy(&env->me_lck->mti_rmutex);
if (rc == 0)
rc = pthread_mutex_destroy(&env->me_lck->mti_wmutex);
assert(rc == 0);
(void)rc;
/* file locks would be released (by kernel)
* while the me_lfd will be closed */
}
}
/* File locks would be released (by kernel) while the file-descriptors
* will be closed. But to avoid false-positive EDEADLK from the kernel,
* locks should be released here explicitly with properly order. */
if (env->me_lfd != INVALID_HANDLE_VALUE)
(void)mdbx_lck_op(env->me_lfd, OP_SETLK, F_UNLCK, 0, OFF_T_MAX);
assert(env->me_fd != INVALID_HANDLE_VALUE);
(void)mdbx_lck_op(env->me_fd, OP_SETLK, F_UNLCK, 0, OFF_T_MAX);
}
static int mdbx_robust_lock(MDBX_env *env, pthread_mutex_t *mutex) {