sync0rw.h

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#else
#define rw_lock_x_unlock_gen(L, P)    rw_lock_x_unlock_func(L)
#endif
/**********************************************************************
Low-level function which locks an rw-lock in s-mode when we know that it
is possible and none else is currently accessing the rw-lock structure.
Then we can do the locking without reserving the mutex. */
UNIV_INLINE
void
rw_lock_s_lock_direct(
/*==================*/
	rw_lock_t*	lock,		/* in: pointer to rw-lock */
	const char*	file_name,	/* in: file name where requested */
	ulint		line		/* in: line where lock requested */
);
/**********************************************************************
Low-level function which locks an rw-lock in x-mode when we know that it
is not locked and none else is currently accessing the rw-lock structure.
Then we can do the locking without reserving the mutex. */
UNIV_INLINE
void
rw_lock_x_lock_direct(
/*==================*/
	rw_lock_t*	lock,		/* in: pointer to rw-lock */
	const char*	file_name,	/* in: file name where requested */
	ulint		line		/* in: line where lock requested */
);
/**********************************************************************
This function is used in the insert buffer to move the ownership of an
x-latch on a buffer frame to the current thread. The x-latch was set by
the buffer read operation and it protected the buffer frame while the
read was done. The ownership is moved because we want that the current
thread is able to acquire a second x-latch which is stored in an mtr.
This, in turn, is needed to pass the debug checks of index page
operations. */

void
rw_lock_x_lock_move_ownership(
/*==========================*/
	rw_lock_t*	lock);	/* in: lock which was x-locked in the
				buffer read */
/**********************************************************************
Releases a shared mode lock when we know there are no waiters and none
else will access the lock during the time this function is executed. */
UNIV_INLINE
void
rw_lock_s_unlock_direct(
/*====================*/
	rw_lock_t*	lock);	/* in: rw-lock */
/**********************************************************************
Releases an exclusive mode lock when we know there are no waiters, and
none else will access the lock durint the time this function is executed. */
UNIV_INLINE
void
rw_lock_x_unlock_direct(
/*====================*/
	rw_lock_t*	lock);	/* in: rw-lock */
/**********************************************************************
Sets the rw-lock latching level field. */

void
rw_lock_set_level(
/*==============*/
	rw_lock_t*	lock,	/* in: rw-lock */
	ulint		level);	/* in: level */
/**********************************************************************
Returns the value of writer_count for the lock. Does not reserve the lock
mutex, so the caller must be sure it is not changed during the call. */
UNIV_INLINE
ulint
rw_lock_get_x_lock_count(
/*=====================*/
				/* out: value of writer_count */
	rw_lock_t*	lock);	/* in: rw-lock */
/************************************************************************
Accessor functions for rw lock. */
UNIV_INLINE
ulint
rw_lock_get_waiters(
/*================*/
	rw_lock_t*	lock);
UNIV_INLINE
ulint
rw_lock_get_writer(
/*===============*/
	rw_lock_t*	lock);
UNIV_INLINE
ulint
rw_lock_get_reader_count(
/*=====================*/
	rw_lock_t*	lock);
#ifdef UNIV_SYNC_DEBUG
/**********************************************************************
Checks if the thread has locked the rw-lock in the specified mode, with
the pass value == 0. */

ibool
rw_lock_own(
/*========*/
	rw_lock_t*	lock,		/* in: rw-lock */
	ulint		lock_type);	/* in: lock type: RW_LOCK_SHARED,
					RW_LOCK_EX */
#endif /* UNIV_SYNC_DEBUG */
/**********************************************************************
Checks if somebody has locked the rw-lock in the specified mode. */

ibool
rw_lock_is_locked(
/*==============*/
	rw_lock_t*	lock,		/* in: rw-lock */
	ulint		lock_type);	/* in: lock type: RW_LOCK_SHARED,
					RW_LOCK_EX */
#ifdef UNIV_SYNC_DEBUG
/*******************************************************************
Prints debug info of an rw-lock. */

void
rw_lock_print(
/*==========*/
	rw_lock_t*	lock);	/* in: rw-lock */
/*******************************************************************
Prints debug info of currently locked rw-locks. */

void
rw_lock_list_print_info(void);
/*=========================*/
/*******************************************************************
Returns the number of currently locked rw-locks.
Works only in the debug version. */

ulint
rw_lock_n_locked(void);
/*==================*/

/*#####################################################################*/

/**********************************************************************
Acquires the debug mutex. We cannot use the mutex defined in sync0sync,
because the debug mutex is also acquired in sync0arr while holding the OS
mutex protecting the sync array, and the ordinary mutex_enter might
recursively call routines in sync0arr, leading to a deadlock on the OS
mutex. */

void
rw_lock_debug_mutex_enter(void);
/*==========================*/
/**********************************************************************
Releases the debug mutex. */

void
rw_lock_debug_mutex_exit(void);
/*==========================*/
/*************************************************************************
Prints info of a debug struct. */

void
rw_lock_debug_print(
/*================*/
	rw_lock_debug_t*	info);	/* in: debug struct */
#endif /* UNIV_SYNC_DEBUG */

/* NOTE! The structure appears here only for the compiler to know its size.
Do not use its fields directly! 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 the lock by setting the writer
field. Then no new readers are allowed in. */

struct rw_lock_struct {
	ulint	reader_count;	/* Number of readers who have locked this
				lock in the shared mode */
	ulint	writer; 	/* This field is set to RW_LOCK_EX if there
				is a writer owning the lock (in exclusive
				mode), RW_LOCK_WAIT_EX if a writer is
				queueing for the lock, and
				RW_LOCK_NOT_LOCKED, otherwise. */
	os_thread_id_t	writer_thread;
				/* Thread id of a possible writer thread */
	ulint	writer_count;	/* Number of times the same thread has
				recursively locked the lock in the exclusive
				mode */
	mutex_t	mutex;		/* The mutex protecting rw_lock_struct */
	ulint	pass; 		/* Default value 0. This is set to some
				value != 0 given by the caller of an x-lock
				operation, if the x-lock is to be passed to
				another thread to unlock (which happens in
				asynchronous i/o). */
	ulint	waiters;	/* This ulint is set to 1 if there are
				waiters (readers or writers) in the global
				wait array, waiting for this rw_lock.
				Otherwise, == 0. */
	ibool	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 */
	UT_LIST_NODE_T(rw_lock_t) list;
				/* All allocated rw locks are put into a
				list */
#ifdef UNIV_SYNC_DEBUG
	UT_LIST_BASE_NODE_T(rw_lock_debug_t) debug_list;
				/* In the debug version: pointer to the debug
				info list of the lock */
#endif /* UNIV_SYNC_DEBUG */
	ulint	level;		/* Level in the global latching
				order; default SYNC_LEVEL_NONE */
	const char*	cfile_name;/* File name where lock created */
	ulint	cline;		/* Line where created */
	const char*	last_s_file_name;/* File name where last s-locked */
	const char*	last_x_file_name;/* File name where last x-locked */
	ulint	last_s_line;	/* Line number where last time s-locked */
	ulint	last_x_line;	/* Line number where last time x-locked */
	ulint	magic_n;
};

#define	RW_LOCK_MAGIC_N	22643

#ifdef UNIV_SYNC_DEBUG
/* The structure for storing debug info of an rw-lock */
struct	rw_lock_debug_struct {

	os_thread_id_t thread_id;  /* The thread id of the thread which
				locked the rw-lock */
	ulint	pass;		/* Pass value given in the lock operation */
	ulint	lock_type;	/* Type of the lock: RW_LOCK_EX,
				RW_LOCK_SHARED, RW_LOCK_WAIT_EX */
	const char*	file_name;/* File name where the lock was obtained */
	ulint	line;		/* Line where the rw-lock was locked */
	UT_LIST_NODE_T(rw_lock_debug_t) list;
				/* Debug structs are linked in a two-way
				list */
};
#endif /* UNIV_SYNC_DEBUG */

#ifndef UNIV_NONINL
#include "sync0rw.ic"
#endif

#endif