/**********************************************************************
Low-level function for acquiring an exclusive lock. */
UNIV_INLINE
ulint
rw_lock_x_lock_low(
/*===============*/
/* out: RW_LOCK_NOT_LOCKED if did
not succeed, RW_LOCK_EX if success,
RW_LOCK_WAIT_EX, if got wait reservation */
rw_lock_t* lock, /* in: pointer to rw-lock */
ulint pass, /* in: pass value; != 0, if the lock will
be passed to another thread to unlock */
const char* file_name,/* in: file name where lock requested */
ulint line) /* in: line where requested */
{
ut_ad(mutex_own(rw_lock_get_mutex(lock)));
if (rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED) {
if (rw_lock_get_reader_count(lock) == 0) {
rw_lock_set_writer(lock, RW_LOCK_EX);
lock->writer_thread = os_thread_get_curr_id();
lock->writer_count++;
lock->pass = pass;
#ifdef UNIV_SYNC_DEBUG
rw_lock_add_debug_info(lock, pass, RW_LOCK_EX,
file_name, line);
#endif
lock->last_x_file_name = file_name;
lock->last_x_line = (unsigned int) line;
/* Locking succeeded, we may return */
return(RW_LOCK_EX);
} else {
/* There are readers, we have to wait */
rw_lock_set_writer(lock, RW_LOCK_WAIT_EX);
lock->writer_thread = os_thread_get_curr_id();
lock->pass = pass;
lock->writer_is_wait_ex = TRUE;
#ifdef UNIV_SYNC_DEBUG
rw_lock_add_debug_info(lock, pass, RW_LOCK_WAIT_EX,
file_name, line);
#endif
return(RW_LOCK_WAIT_EX);
}
} else if ((rw_lock_get_writer(lock) == RW_LOCK_WAIT_EX)
&& os_thread_eq(lock->writer_thread,
os_thread_get_curr_id())) {
if (rw_lock_get_reader_count(lock) == 0) {
rw_lock_set_writer(lock, RW_LOCK_EX);
lock->writer_count++;
lock->pass = pass;
lock->writer_is_wait_ex = FALSE;
#ifdef UNIV_SYNC_DEBUG
rw_lock_remove_debug_info(lock, pass, RW_LOCK_WAIT_EX);
rw_lock_add_debug_info(lock, pass, RW_LOCK_EX,
file_name, line);
#endif
lock->last_x_file_name = file_name;
lock->last_x_line = (unsigned int) line;
/* Locking succeeded, we may return */
return(RW_LOCK_EX);
}
return(RW_LOCK_WAIT_EX);
} else if ((rw_lock_get_writer(lock) == RW_LOCK_EX)
&& os_thread_eq(lock->writer_thread,
os_thread_get_curr_id())
&& (lock->pass == 0)
&& (pass == 0)) {
lock->writer_count++;
#ifdef UNIV_SYNC_DEBUG
rw_lock_add_debug_info(lock, pass, RW_LOCK_EX, file_name,
line);
#endif
lock->last_x_file_name = file_name;
lock->last_x_line = (unsigned int) line;
/* Locking succeeded, we may return */
return(RW_LOCK_EX);
}
/* Locking did not succeed */
return(RW_LOCK_NOT_LOCKED);
}
/******************************************************************//**
Function for the next writer to call. Waits for readers to exit.
The caller must have already decremented lock_word by X_LOCK_DECR. */
UNIV_INLINE
void
rw_lock_x_lock_wait(
/*================*/
rw_lock_t* lock, /*!< in: pointer to rw-lock */
#ifdef UNIV_SYNC_DEBUG
ulint pass, /*!< in: pass value; != 0, if the lock will
be passed to another thread to unlock */
#endif
const char* file_name,/*!< in: file name where lock requested */
ulint line) /*!< in: line where requested */
{
ulint index;
ulint i = 0;
ut_ad(lock->lock_word <= 0);
while (lock->lock_word < 0) {
if (srv_spin_wait_delay) {
ut_delay(ut_rnd_interval(0, srv_spin_wait_delay));
}
if(i < SYNC_SPIN_ROUNDS) {
i++;
continue;
}
/* If there is still a reader, then go to sleep.*/
rw_x_spin_round_count += i;
i = 0;
sync_array_reserve_cell(sync_primary_wait_array,
lock,
RW_LOCK_WAIT_EX,
file_name, line,
&index);
/* Check lock_word to ensure wake-up isn't missed.*/
if(lock->lock_word < 0) {
/* these stats may not be accurate */
lock->count_os_wait++;
rw_x_os_wait_count++;
/* Add debug info as it is needed to detect possible
deadlock. We must add info for WAIT_EX thread for
deadlock detection to work properly. */
#ifdef UNIV_SYNC_DEBUG
rw_lock_add_debug_info(lock, pass, RW_LOCK_WAIT_EX,
file_name, line);
#endif
sync_array_wait_event(sync_primary_wait_array,
index);
#ifdef UNIV_SYNC_DEBUG
rw_lock_remove_debug_info(lock, pass,
RW_LOCK_WAIT_EX);
#endif
/* It is possible to wake when lock_word < 0.
We must pass the while-loop check to proceed.*/
} else {
sync_array_free_cell(sync_primary_wait_array,
index);
}
}
rw_x_spin_round_count += i;
}
