#include <sync0rw.h>
Data Fields | |
| volatile lint | lock_word |
| volatile ulint | waiters |
| volatile ibool | recursive |
| volatile os_thread_id_t | writer_thread |
| os_event_t | event |
| os_event_t | wait_ex_event |
| ib_mutex_t | mutex |
| ut_list_node< rw_lock_t > | list |
| ut_list_base< rw_lock_debug_t > | debug_list |
| ulint | level |
| ulint | count_os_wait |
| const char * | cfile_name |
| const char * | last_s_file_name |
| const char * | last_x_file_name |
| ibool | writer_is_wait_ex |
| unsigned | cline:14 |
| unsigned | last_s_line:14 |
| unsigned | last_x_line:14 |
| ulint | magic_n |
Detailed Description
The structure used in the spin lock implementation of a read-write
lock. Several threads may have a shared lock simultaneously in this lock, but only one writer may have an exclusive lock, in which case no shared locks are allowed. To prevent starving of a writer blocked by readers, a writer may queue for x-lock by decrementing lock_word: no new readers will be let in while the thread waits for readers to exit.
Field Documentation
| const char* rw_lock_t::cfile_name |
File name where lock created
| unsigned rw_lock_t::cline |
Line where created
| ulint rw_lock_t::count_os_wait |
Count of os_waits. May not be accurate
| ut_list_base< rw_lock_debug_t > rw_lock_t::debug_list |
In the debug version: pointer to the debug info list of the lock
| os_event_t rw_lock_t::event |
Used by sync0arr.cc for thread queueing
| const char* rw_lock_t::last_s_file_name |
File name where last s-locked
| unsigned rw_lock_t::last_s_line |
Line number where last time s-locked
| const char* rw_lock_t::last_x_file_name |
File name where last x-locked
| unsigned rw_lock_t::last_x_line |
Line number where last time x-locked
| ulint rw_lock_t::level |
Level in the global latching order.
| ut_list_node< rw_lock_t > rw_lock_t::list |
All allocated rw locks are put into a list
| volatile lint rw_lock_t::lock_word |
Holds the state of the lock.
| ulint rw_lock_t::magic_n |
RW_LOCK_MAGIC_N
| ib_mutex_t rw_lock_t::mutex |
The mutex protecting rw_lock_t
| volatile ibool rw_lock_t::recursive |
Default value FALSE which means the lock is non-recursive. The value is typically set to TRUE making normal rw_locks recursive. In case of asynchronous IO, when a non-zero value of 'pass' is passed then we keep the lock non-recursive. This flag also tells us about the state of writer_thread field. If this flag is set then writer_thread MUST contain the thread id of the current x-holder or wait-x thread. This flag must be reset in x_unlock functions before incrementing the lock_word
| os_event_t rw_lock_t::wait_ex_event |
Event for next-writer to wait on. A thread must decrement lock_word before waiting.
| volatile ulint rw_lock_t::waiters |
1: there are waiters
| ibool rw_lock_t::writer_is_wait_ex |
This is TRUE if the writer field is RW_LOCK_WAIT_EX; this field is located far from the memory update hotspot fields which are at the start of this struct, thus we can peek this field without causing much memory bus traffic
| volatile os_thread_id_t rw_lock_t::writer_thread |
Thread id of writer thread. Is only guaranteed to have sane and non-stale value iff recursive flag is set.
The documentation for this struct was generated from the following file:
- include/sync0rw.h
