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mdbx: use flock() for share/exclusive lck.

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This commit is contained in:
Leo Yuriev 2017-05-18 14:00:40 +03:00
parent 1431e3e5bf
commit 6ee3aebc32
2 changed files with 51 additions and 34 deletions
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84
src/lck-posix.c
View File

@ -74,6 +74,50 @@ static int mdbx_lck_op(mdbx_filehandle_t fd, int op, int lck, off_t offset,
}
}
static __inline int mdbx_lck_exclusive(int lfd) {
assert(lfd != INVALID_HANDLE_VALUE);
if (flock(lfd, LOCK_EX | LOCK_NB))
return errno;
return mdbx_lck_op(lfd, F_SETLK, F_WRLCK, 0, 1);
}
static __inline int mdbx_lck_shared(int lfd) {
assert(lfd != INVALID_HANDLE_VALUE);
while (flock(lfd, LOCK_SH)) {
int rc = errno;
if (rc != EINTR)
return rc;
}
return mdbx_lck_op(lfd, F_SETLKW, F_RDLCK, 0, 1);
}
int mdbx_lck_downgrade(MDB_env *env) { return mdbx_lck_shared(env->me_lfd); }
int mdbx_rpid_set(MDB_env *env) {
return mdbx_lck_op(env->me_lfd, F_SETLK, F_WRLCK, env->me_pid, 1);
}
int mdbx_rpid_clear(MDB_env *env) {
return mdbx_lck_op(env->me_lfd, F_SETLKW, F_UNLCK, env->me_pid, 1);
}
/* Checks reader by pid.
*
* Returns:
* MDBX_RESULT_TRUE, if pid is live (unable to acquire lock)
* MDBX_RESULT_FALSE, if pid is dead (lock acquired)
* or otherwise the errcode. */
int mdbx_rpid_check(MDB_env *env, mdbx_pid_t pid) {
int rc = mdbx_lck_op(env->me_lfd, F_GETLK, F_WRLCK, pid, 1);
if (rc == 0)
return MDBX_RESULT_FALSE;
if (rc < 0 && -rc == pid)
return MDBX_RESULT_TRUE;
return rc;
}
/*---------------------------------------------------------------------------*/
static int mdbx_mutex_failed(MDB_env *env, pthread_mutex_t *mutex, int rc);
int mdbx_lck_init(MDB_env *env) {
@ -117,8 +161,7 @@ bailout:
void mdbx_lck_destroy(MDB_env *env) {
if (env->me_lfd != INVALID_HANDLE_VALUE) {
/* try get exclusive access */
if (env->me_lck &&
mdbx_lck_op(env->me_lfd, F_SETLK, F_WRLCK, 0, LCK_WHOLE) == 0) {
if (env->me_lck && mdbx_lck_exclusive(env->me_lfd) == 0) {
/* got exclusive, drown mutexes */
int rc = pthread_mutex_destroy(&env->me_lck->mti_rmutex);
if (rc == 0)
@ -169,20 +212,20 @@ static int internal_seize_lck(int lfd) {
assert(lfd != INVALID_HANDLE_VALUE);
/* try exclusive access */
int rc = mdbx_lck_op(lfd, F_SETLK, F_WRLCK, 0, 1);
int rc = mdbx_lck_exclusive(lfd);
if (rc == 0)
/* got exclusive */
return MDBX_RESULT_TRUE;
if (rc == EAGAIN || rc == EACCES || rc == EBUSY) {
if (rc == EAGAIN || rc == EACCES || rc == EBUSY || rc == EWOULDBLOCK) {
/* get shared access */
rc = mdbx_lck_op(lfd, F_SETLKW, F_RDLCK, 0, 1);
rc = mdbx_lck_shared(lfd);
if (rc == 0) {
/* got shared, try exclusive again */
rc = mdbx_lck_op(lfd, F_SETLK, F_WRLCK, 0, 1);
rc = mdbx_lck_exclusive(lfd);
if (rc == 0)
/* now got exclusive */
return MDBX_RESULT_TRUE;
if (rc == EAGAIN || rc == EACCES || rc == EBUSY)
if (rc == EAGAIN || rc == EACCES || rc == EBUSY || rc == EWOULDBLOCK)
/* unable exclusive, but stay shared */
return MDBX_RESULT_FALSE;
}
@ -217,33 +260,6 @@ int mdbx_lck_seize(MDB_env *env) {
return internal_seize_lck(env->me_lfd);
}
int mdbx_lck_downgrade(MDB_env *env) {
return mdbx_lck_op(env->me_lfd, F_SETLK, F_RDLCK, 0, 1);
}
int mdbx_rpid_set(MDB_env *env) {
return mdbx_lck_op(env->me_lfd, F_SETLK, F_WRLCK, env->me_pid, 1);
}
int mdbx_rpid_clear(MDB_env *env) {
return mdbx_lck_op(env->me_lfd, F_SETLKW, F_UNLCK, env->me_pid, 1);
}
/* Checks reader by pid.
*
* Returns:
* MDBX_RESULT_TRUE, if pid is live (unable to acquire lock)
* MDBX_RESULT_FALSE, if pid is dead (lock acquired)
* or otherwise the errcode. */
int mdbx_rpid_check(MDB_env *env, mdbx_pid_t pid) {
int rc = mdbx_lck_op(env->me_lfd, F_GETLK, F_WRLCK, pid, 1);
if (rc == 0)
return MDBX_RESULT_FALSE;
if (rc < 0 && -rc == pid)
return MDBX_RESULT_TRUE;
return rc;
}
#if !__GLIBC_PREREQ(2, 12) && !defined(pthread_mutex_consistent)
#define pthread_mutex_consistent(mutex) pthread_mutex_consistent_np(mutex)
#endif

1
src/osal.h
View File

@ -68,6 +68,7 @@ typedef SSIZE_T ssize_t;
#define THREAD_RESULT DWORD
#else
#include <pthread.h>
#include <sys/file.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/stat.h>