path: root/storage/innodb_plugin/os/os0sync.c

/*****************************************************************************

Copyright (c) 1995, 2009, Innobase Oy. All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place, Suite 330, Boston, MA 02111-1307 USA

*****************************************************************************/

/**************************************************//**
@file os/os0sync.c
The interface to the operating system
synchronization primitives.

Created 9/6/1995 Heikki Tuuri
*******************************************************/

#include "os0sync.h"
#ifdef UNIV_NONINL
#include "os0sync.ic"
#endif

#ifdef __WIN__
#include <windows.h>
#endif

#include "ut0mem.h"
#include "srv0start.h"

/* Type definition for an operating system mutex struct */
struct os_mutex_struct{
	os_event_t	event;	/*!< Used by sync0arr.c for queing threads */
	void*		handle;	/*!< OS handle to mutex */
	ulint		count;	/*!< we use this counter to check
				that the same thread does not
				recursively lock the mutex: we
				do not assume that the OS mutex
				supports recursive locking, though
				NT seems to do that */
	UT_LIST_NODE_T(os_mutex_str_t) os_mutex_list;
				/* list of all 'slow' OS mutexes created */
};

/** Mutex protecting counts and the lists of OS mutexes and events */
UNIV_INTERN os_mutex_t	os_sync_mutex;
/** TRUE if os_sync_mutex has been initialized */
static ibool		os_sync_mutex_inited	= FALSE;
/** TRUE when os_sync_free() is being executed */
static ibool		os_sync_free_called	= FALSE;

/** This is incremented by 1 in os_thread_create and decremented by 1 in
os_thread_exit */
UNIV_INTERN ulint	os_thread_count		= 0;

/** The list of all events created */
static UT_LIST_BASE_NODE_T(os_event_struct_t)	os_event_list;

/** The list of all OS 'slow' mutexes */
static UT_LIST_BASE_NODE_T(os_mutex_str_t)	os_mutex_list;

UNIV_INTERN ulint	os_event_count		= 0;
UNIV_INTERN ulint	os_mutex_count		= 0;
UNIV_INTERN ulint	os_fast_mutex_count	= 0;

/* Because a mutex is embedded inside an event and there is an
event embedded inside a mutex, on free, this generates a recursive call.
This version of the free event function doesn't acquire the global lock */
static void os_event_free_internal(os_event_t	event);

/*********************************************************//**
Initializes global event and OS 'slow' mutex lists. */
UNIV_INTERN
void
os_sync_init(void)
/*==============*/
{
	UT_LIST_INIT(os_event_list);
	UT_LIST_INIT(os_mutex_list);

	os_sync_mutex = os_mutex_create(NULL);

	os_sync_mutex_inited = TRUE;
}

/*********************************************************//**
Frees created events and OS 'slow' mutexes. */
UNIV_INTERN
void
os_sync_free(void)
/*==============*/
{
	os_event_t	event;
	os_mutex_t	mutex;

	os_sync_free_called = TRUE;
	event = UT_LIST_GET_FIRST(os_event_list);

	while (event) {

		os_event_free(event);

		event = UT_LIST_GET_FIRST(os_event_list);
	}

	mutex = UT_LIST_GET_FIRST(os_mutex_list);

	while (mutex) {
		if (mutex == os_sync_mutex) {
			/* Set the flag to FALSE so that we do not try to
			reserve os_sync_mutex any more in remaining freeing
			operations in shutdown */
			os_sync_mutex_inited = FALSE;
		}

		os_mutex_free(mutex);

		mutex = UT_LIST_GET_FIRST(os_mutex_list);
	}
	os_sync_free_called = FALSE;
}

/*********************************************************//**
Creates an event semaphore, i.e., a semaphore which may just have two
states: signaled and nonsignaled. The created event is manual reset: it
must be reset explicitly by calling sync_os_reset_event.
@return	the event handle */
UNIV_INTERN
os_event_t
os_event_create(
/*============*/
	const char*	name)	/*!< in: the name of the event, if NULL
				the event is created without a name */
{
#ifdef __WIN__
	os_event_t event;

	event = ut_malloc(sizeof(struct os_event_struct));

	event->handle = CreateEvent(NULL, /* No security attributes */
				    TRUE, /* Manual reset */
				    FALSE, /* Initial state nonsignaled */
				    (LPCTSTR) name);
	if (!event->handle) {
		fprintf(stderr,
			"InnoDB: Could not create a Windows event semaphore;"
			" Windows error %lu\n",
			(ulong) GetLastError());
	}
#else /* Unix */
	os_event_t	event;

	UT_NOT_USED(name);

	event = ut_malloc(sizeof(struct os_event_struct));

	os_fast_mutex_init(&(event->os_mutex));

	ut_a(0 == pthread_cond_init(&(event->cond_var), NULL));

	event->is_set = FALSE;

	/* We return this value in os_event_reset(), which can then be
	be used to pass to the os_event_wait_low(). The value of zero
	is reserved in os_event_wait_low() for the case when the
	caller does not want to pass any signal_count value. To
	distinguish between the two cases we initialize signal_count
	to 1 here. */
	event->signal_count = 1;
#endif /* __WIN__ */

	/* The os_sync_mutex can be NULL because during startup an event
	can be created [ because it's embedded in the mutex/rwlock ] before
	this module has been initialized */
	if (os_sync_mutex != NULL) {
		os_mutex_enter(os_sync_mutex);
	}

	/* Put to the list of events */
	UT_LIST_ADD_FIRST(os_event_list, os_event_list, event);

	os_event_count++;

	if (os_sync_mutex != NULL) {
		os_mutex_exit(os_sync_mutex);
	}

	return(event);
}

/**********************************************************//**
Sets an event semaphore to the signaled state: lets waiting threads
proceed. */
UNIV_INTERN
void
os_event_set(
/*=========*/
	os_event_t	event)	/*!< in: event to set */
{
#ifdef __WIN__
	ut_a(event);
	ut_a(SetEvent(event->handle));
#else
	ut_a(event);

	os_fast_mutex_lock(&(event->os_mutex));

	if (event->is_set) {
		/* Do nothing */
	} else {
		event->is_set = TRUE;
		event->signal_count += 1;
		ut_a(0 == pthread_cond_broadcast(&(event->cond_var)));
	}

	os_fast_mutex_unlock(&(event->os_mutex));
#endif
}

/**********************************************************//**
Resets an event semaphore to the nonsignaled state. Waiting threads will
stop to wait for the event.
The return value should be passed to os_even_wait_low() if it is desired
that this thread should not wait in case of an intervening call to
os_event_set() between this os_event_reset() and the
os_event_wait_low() call. See comments for os_event_wait_low().
@return	current signal_count. */
UNIV_INTERN
ib_int64_t
os_event_reset(
/*===========*/
	os_event_t	event)	/*!< in: event to reset */
{
	ib_int64_t	ret = 0;

#ifdef __WIN__
	ut_a(event);

	ut_a(ResetEvent(event->handle));
#else
	ut_a(event);

	os_fast_mutex_lock(&(event->os_mutex));

	if (!event->is_set) {
		/* Do nothing */
	} else {
		event->is_set = FALSE;
	}
	ret = event->signal_count;

	os_fast_mutex_unlock(&(event->os_mutex));
#endif
	return(ret);
}

/**********************************************************//**
Frees an event object, without acquiring the global lock. */
static
void
os_event_free_internal(
/*===================*/
	os_event_t	event)	/*!< in: event to free */
{
#ifdef __WIN__
	ut_a(event);

	ut_a(CloseHandle(event->handle));
#else
	ut_a(event);

	/* This is to avoid freeing the mutex twice */
	os_fast_mutex_free(&(event->os_mutex));

	ut_a(0 == pthread_cond_destroy(&(event->cond_var)));
#endif
	/* Remove from the list of events */

	UT_LIST_REMOVE(os_event_list, os_event_list, event);

	os_event_count--;

	ut_free(event);
}

/**********************************************************//**
Frees an event object. */
UNIV_INTERN
void
os_event_free(
/*==========*/
	os_event_t	event)	/*!< in: event to free */

{
#ifdef __WIN__
	ut_a(event);

	ut_a(CloseHandle(event->handle));
#else
	ut_a(event);

	os_fast_mutex_free(&(event->os_mutex));
	ut_a(0 == pthread_cond_destroy(&(event->cond_var)));
#endif
	/* Remove from the list of events */

	os_mutex_enter(os_sync_mutex);

	UT_LIST_REMOVE(os_event_list, os_event_list, event);

	os_event_count--;

	os_mutex_exit(os_sync_mutex);

	ut_free(event);
}

/**********************************************************//**
Waits for an event object until it is in the signaled state. If
srv_shutdown_state == SRV_SHUTDOWN_EXIT_THREADS this also exits the
waiting thread when the event becomes signaled (or immediately if the
event is already in the signaled state).

Typically, if the event has been signalled after the os_event_reset()
we'll return immediately because event->is_set == TRUE.
There are, however, situations (e.g.: sync_array code) where we may
lose this information. For example:

thread A calls os_event_reset()
thread B calls os_event_set()   [event->is_set == TRUE]
thread C calls os_event_reset() [event->is_set == FALSE]
thread A calls os_event_wait()  [infinite wait!]
thread C calls os_event_wait()  [infinite wait!]

Where such a scenario is possible, to avoid infinite wait, the
value returned by os_event_reset() should be passed in as
reset_sig_count. */
UNIV_INTERN
void
os_event_wait_low(
/*==============*/
	os_event_t	event,		/*!< in: event to wait */
	ib_int64_t	reset_sig_count)/*!< in: zero or the value
					returned by previous call of
					os_event_reset(). */
{
#ifdef __WIN__
	DWORD	err;

	ut_a(event);

	UT_NOT_USED(reset_sig_count);

	/* Specify an infinite time limit for waiting */
	err = WaitForSingleObject(event->handle, INFINITE);

	ut_a(err == WAIT_OBJECT_0);

	if (srv_shutdown_state == SRV_SHUTDOWN_EXIT_THREADS) {
		os_thread_exit(NULL);
	}
#else
	ib_int64_t	old_signal_count;

	os_fast_mutex_lock(&(event->os_mutex));

	if (reset_sig_count) {
		old_signal_count = reset_sig_count;
	} else {
		old_signal_count = event->signal_count;
	}

	for (;;) {
		if (event->is_set == TRUE
		    || event->signal_count != old_signal_count) {

			os_fast_mutex_unlock(&(event->os_mutex));

			if (srv_shutdown_state == SRV_SHUTDOWN_EXIT_THREADS) {

				os_thread_exit(NULL);
			}
			/* Ok, we may return */

			return;
		}

		pthread_cond_wait(&(event->cond_var), &(event->os_mutex));

		/* Solaris manual said that spurious wakeups may occur: we
		have to check if the event really has been signaled after
		we came here to wait */
	}
#endif
}

/**********************************************************//**
Waits for an event object until it is in the signaled state or
a timeout is exceeded. In Unix the timeout is always infinite.
@return	0 if success, OS_SYNC_TIME_EXCEEDED if timeout was exceeded */
UNIV_INTERN
ulint
os_event_wait_time(
/*===============*/
	os_event_t	event,	/*!< in: event to wait */
	ulint		time)	/*!< in: timeout in microseconds, or
				OS_SYNC_INFINITE_TIME */
{
#ifdef __WIN__
	DWORD	err;

	ut_a(event);

	if (time != OS_SYNC_INFINITE_TIME) {
		err = WaitForSingleObject(event->handle, (DWORD) time / 1000);
	} else {
		err = WaitForSingleObject(event->handle, INFINITE);
	}

	if (err == WAIT_OBJECT_0) {

		return(0);
	} else if (err == WAIT_TIMEOUT) {

		return(OS_SYNC_TIME_EXCEEDED);
	} else {
		ut_error;
		return(1000000); /* dummy value to eliminate compiler warn. */
	}
#else
	UT_NOT_USED(time);

	/* In Posix this is just an ordinary, infinite wait */

	os_event_wait(event);

	return(0);
#endif
}

#ifdef __WIN__
/**********************************************************//**
Waits for any event in an OS native event array. Returns if even a single
one is signaled or becomes signaled.
@return	index of the event which was signaled */
UNIV_INTERN
ulint
os_event_wait_multiple(
/*===================*/
	ulint			n,	/*!< in: number of events in the
					array */
	os_native_event_t*	native_event_array)
					/*!< in: pointer to an array of event
					handles */
{
	DWORD	index;

	ut_a(native_event_array);
	ut_a(n > 0);

	index = WaitForMultipleObjects((DWORD) n, native_event_array,
				       FALSE,	   /* Wait for any 1 event */
				       INFINITE); /* Infinite wait time
						  limit */
	ut_a(index >= WAIT_OBJECT_0);	/* NOTE: Pointless comparison */
	ut_a(index < WAIT_OBJECT_0 + n);

	if (srv_shutdown_state == SRV_SHUTDOWN_EXIT_THREADS) {
		os_thread_exit(NULL);
	}

	return(index - WAIT_OBJECT_0);
}
#endif

/*********************************************************//**
Creates an operating system mutex semaphore. Because these are slow, the
mutex semaphore of InnoDB itself (mutex_t) should be used where possible.
@return	the mutex handle */
UNIV_INTERN
os_mutex_t
os_mutex_create(
/*============*/
	const char*	name)	/*!< in: the name of the mutex, if NULL
				the mutex is created without a name */
{
#ifdef __WIN__
	HANDLE		mutex;
	os_mutex_t	mutex_str;

	mutex = CreateMutex(NULL,	/* No security attributes */
			    FALSE,		/* Initial state: no owner */
			    (LPCTSTR) name);
	ut_a(mutex);
#else
	os_fast_mutex_t*	mutex;
	os_mutex_t		mutex_str;

	UT_NOT_USED(name);

	mutex = ut_malloc(sizeof(os_fast_mutex_t));

	os_fast_mutex_init(mutex);
#endif
	mutex_str = ut_malloc(sizeof(os_mutex_str_t));

	mutex_str->handle = mutex;
	mutex_str->count = 0;
	mutex_str->event = os_event_create(NULL);

	if (UNIV_LIKELY(os_sync_mutex_inited)) {
		/* When creating os_sync_mutex itself we cannot reserve it */
		os_mutex_enter(os_sync_mutex);
	}

	UT_LIST_ADD_FIRST(os_mutex_list, os_mutex_list, mutex_str);

	os_mutex_count++;

	if (UNIV_LIKELY(os_sync_mutex_inited)) {
		os_mutex_exit(os_sync_mutex);
	}

	return(mutex_str);
}

/**********************************************************//**
Acquires ownership of a mutex semaphore. */
UNIV_INTERN
void
os_mutex_enter(
/*===========*/
	os_mutex_t	mutex)	/*!< in: mutex to acquire */
{
#ifdef __WIN__
	DWORD	err;

	ut_a(mutex);

	/* Specify infinite time limit for waiting */
	err = WaitForSingleObject(mutex->handle, INFINITE);

	ut_a(err == WAIT_OBJECT_0);

	(mutex->count)++;
	ut_a(mutex->count == 1);
#else
	os_fast_mutex_lock(mutex->handle);

	(mutex->count)++;

	ut_a(mutex->count == 1);
#endif
}

/**********************************************************//**
Releases ownership of a mutex. */
UNIV_INTERN
void
os_mutex_exit(
/*==========*/
	os_mutex_t	mutex)	/*!< in: mutex to release */
{
	ut_a(mutex);

	ut_a(mutex->count == 1);

	(mutex->count)--;
#ifdef __WIN__
	ut_a(ReleaseMutex(mutex->handle));
#else
	os_fast_mutex_unlock(mutex->handle);
#endif
}

/**********************************************************//**
Frees a mutex object. */
UNIV_INTERN
void
os_mutex_free(
/*==========*/
	os_mutex_t	mutex)	/*!< in: mutex to free */
{
	ut_a(mutex);

	if (UNIV_LIKELY(!os_sync_free_called)) {
		os_event_free_internal(mutex->event);
	}

	if (UNIV_LIKELY(os_sync_mutex_inited)) {
		os_mutex_enter(os_sync_mutex);
	}

	UT_LIST_REMOVE(os_mutex_list, os_mutex_list, mutex);

	os_mutex_count--;

	if (UNIV_LIKELY(os_sync_mutex_inited)) {
		os_mutex_exit(os_sync_mutex);
	}

#ifdef __WIN__
	ut_a(CloseHandle(mutex->handle));

	ut_free(mutex);
#else
	os_fast_mutex_free(mutex->handle);
	ut_free(mutex->handle);
	ut_free(mutex);
#endif
}

/*********************************************************//**
Initializes an operating system fast mutex semaphore. */
UNIV_INTERN
void
os_fast_mutex_init(
/*===============*/
	os_fast_mutex_t*	fast_mutex)	/*!< in: fast mutex */
{
#ifdef __WIN__
	ut_a(fast_mutex);

	InitializeCriticalSection((LPCRITICAL_SECTION) fast_mutex);
#else
	ut_a(0 == pthread_mutex_init(fast_mutex, MY_MUTEX_INIT_FAST));
#endif
	if (UNIV_LIKELY(os_sync_mutex_inited)) {
		/* When creating os_sync_mutex itself (in Unix) we cannot
		reserve it */

		os_mutex_enter(os_sync_mutex);
	}

	os_fast_mutex_count++;

	if (UNIV_LIKELY(os_sync_mutex_inited)) {
		os_mutex_exit(os_sync_mutex);
	}
}

/**********************************************************//**
Acquires ownership of a fast mutex. */
UNIV_INTERN
void
os_fast_mutex_lock(
/*===============*/
	os_fast_mutex_t*	fast_mutex)	/*!< in: mutex to acquire */
{
#ifdef __WIN__
	EnterCriticalSection((LPCRITICAL_SECTION) fast_mutex);
#else
	pthread_mutex_lock(fast_mutex);
#endif
}

/**********************************************************//**
Releases ownership of a fast mutex. */
UNIV_INTERN
void
os_fast_mutex_unlock(
/*=================*/
	os_fast_mutex_t*	fast_mutex)	/*!< in: mutex to release */
{
#ifdef __WIN__
	LeaveCriticalSection(fast_mutex);
#else
	pthread_mutex_unlock(fast_mutex);
#endif
}

/**********************************************************//**
Frees a mutex object. */
UNIV_INTERN
void
os_fast_mutex_free(
/*===============*/
	os_fast_mutex_t*	fast_mutex)	/*!< in: mutex to free */
{
#ifdef __WIN__
	ut_a(fast_mutex);

	DeleteCriticalSection((LPCRITICAL_SECTION) fast_mutex);
#else
	int	ret;

	ret = pthread_mutex_destroy(fast_mutex);

	if (UNIV_UNLIKELY(ret != 0)) {
		ut_print_timestamp(stderr);
		fprintf(stderr,
			"  InnoDB: error: return value %lu when calling\n"
			"InnoDB: pthread_mutex_destroy().\n", (ulint)ret);
		fprintf(stderr,
			"InnoDB: Byte contents of the pthread mutex at %p:\n",
			(void*) fast_mutex);
		ut_print_buf(stderr, fast_mutex, sizeof(os_fast_mutex_t));
		putc('\n', stderr);
	}
#endif
	if (UNIV_LIKELY(os_sync_mutex_inited)) {
		/* When freeing the last mutexes, we have
		already freed os_sync_mutex */

		os_mutex_enter(os_sync_mutex);
	}

	os_fast_mutex_count--;

	if (UNIV_LIKELY(os_sync_mutex_inited)) {
		os_mutex_exit(os_sync_mutex);
	}
}