linux_dsm_epyc7002/include/linux/workqueue.h
Oleg Nesterov db70089722 workqueues: implement flush_work()
Most of users of flush_workqueue() can be changed to use cancel_work_sync(),
but sometimes we really need to wait for the completion and cancelling is not
an option. schedule_on_each_cpu() is good example.

Add the new helper, flush_work(work), which waits for the completion of the
specific work_struct. More precisely, it "flushes" the result of of the last
queue_work() which is visible to the caller.

For example, this code

	queue_work(wq, work);
	/* WINDOW */
	queue_work(wq, work);

	flush_work(work);

doesn't necessary work "as expected". What can happen in the WINDOW above is

	- wq starts the execution of work->func()

	- the caller migrates to another CPU

now, after the 2nd queue_work() this work is active on the previous CPU, and
at the same time it is queued on another. In this case flush_work(work) may
return before the first work->func() completes.

It is trivial to add another helper

	int flush_work_sync(struct work_struct *work)
	{
		return flush_work(work) || wait_on_work(work);
	}

which works "more correctly", but it has to iterate over all CPUs and thus
it much slower than flush_work().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Max Krasnyansky <maxk@qualcomm.com>
Acked-by: Jarek Poplawski <jarkao2@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-25 10:53:40 -07:00

242 lines
6.6 KiB
C

/*
* workqueue.h --- work queue handling for Linux.
*/
#ifndef _LINUX_WORKQUEUE_H
#define _LINUX_WORKQUEUE_H
#include <linux/timer.h>
#include <linux/linkage.h>
#include <linux/bitops.h>
#include <linux/lockdep.h>
#include <asm/atomic.h>
struct workqueue_struct;
struct work_struct;
typedef void (*work_func_t)(struct work_struct *work);
/*
* The first word is the work queue pointer and the flags rolled into
* one
*/
#define work_data_bits(work) ((unsigned long *)(&(work)->data))
struct work_struct {
atomic_long_t data;
#define WORK_STRUCT_PENDING 0 /* T if work item pending execution */
#define WORK_STRUCT_FLAG_MASK (3UL)
#define WORK_STRUCT_WQ_DATA_MASK (~WORK_STRUCT_FLAG_MASK)
struct list_head entry;
work_func_t func;
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
};
#define WORK_DATA_INIT() ATOMIC_LONG_INIT(0)
struct delayed_work {
struct work_struct work;
struct timer_list timer;
};
struct execute_work {
struct work_struct work;
};
#ifdef CONFIG_LOCKDEP
/*
* NB: because we have to copy the lockdep_map, setting _key
* here is required, otherwise it could get initialised to the
* copy of the lockdep_map!
*/
#define __WORK_INIT_LOCKDEP_MAP(n, k) \
.lockdep_map = STATIC_LOCKDEP_MAP_INIT(n, k),
#else
#define __WORK_INIT_LOCKDEP_MAP(n, k)
#endif
#define __WORK_INITIALIZER(n, f) { \
.data = WORK_DATA_INIT(), \
.entry = { &(n).entry, &(n).entry }, \
.func = (f), \
__WORK_INIT_LOCKDEP_MAP(#n, &(n)) \
}
#define __DELAYED_WORK_INITIALIZER(n, f) { \
.work = __WORK_INITIALIZER((n).work, (f)), \
.timer = TIMER_INITIALIZER(NULL, 0, 0), \
}
#define DECLARE_WORK(n, f) \
struct work_struct n = __WORK_INITIALIZER(n, f)
#define DECLARE_DELAYED_WORK(n, f) \
struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f)
/*
* initialize a work item's function pointer
*/
#define PREPARE_WORK(_work, _func) \
do { \
(_work)->func = (_func); \
} while (0)
#define PREPARE_DELAYED_WORK(_work, _func) \
PREPARE_WORK(&(_work)->work, (_func))
/*
* initialize all of a work item in one go
*
* NOTE! No point in using "atomic_long_set()": useing a direct
* assignment of the work data initializer allows the compiler
* to generate better code.
*/
#ifdef CONFIG_LOCKDEP
#define INIT_WORK(_work, _func) \
do { \
static struct lock_class_key __key; \
\
(_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
lockdep_init_map(&(_work)->lockdep_map, #_work, &__key, 0);\
INIT_LIST_HEAD(&(_work)->entry); \
PREPARE_WORK((_work), (_func)); \
} while (0)
#else
#define INIT_WORK(_work, _func) \
do { \
(_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
INIT_LIST_HEAD(&(_work)->entry); \
PREPARE_WORK((_work), (_func)); \
} while (0)
#endif
#define INIT_DELAYED_WORK(_work, _func) \
do { \
INIT_WORK(&(_work)->work, (_func)); \
init_timer(&(_work)->timer); \
} while (0)
#define INIT_DELAYED_WORK_DEFERRABLE(_work, _func) \
do { \
INIT_WORK(&(_work)->work, (_func)); \
init_timer_deferrable(&(_work)->timer); \
} while (0)
/**
* work_pending - Find out whether a work item is currently pending
* @work: The work item in question
*/
#define work_pending(work) \
test_bit(WORK_STRUCT_PENDING, work_data_bits(work))
/**
* delayed_work_pending - Find out whether a delayable work item is currently
* pending
* @work: The work item in question
*/
#define delayed_work_pending(w) \
work_pending(&(w)->work)
/**
* work_clear_pending - for internal use only, mark a work item as not pending
* @work: The work item in question
*/
#define work_clear_pending(work) \
clear_bit(WORK_STRUCT_PENDING, work_data_bits(work))
extern struct workqueue_struct *
__create_workqueue_key(const char *name, int singlethread,
int freezeable, struct lock_class_key *key,
const char *lock_name);
#ifdef CONFIG_LOCKDEP
#define __create_workqueue(name, singlethread, freezeable) \
({ \
static struct lock_class_key __key; \
const char *__lock_name; \
\
if (__builtin_constant_p(name)) \
__lock_name = (name); \
else \
__lock_name = #name; \
\
__create_workqueue_key((name), (singlethread), \
(freezeable), &__key, \
__lock_name); \
})
#else
#define __create_workqueue(name, singlethread, freezeable) \
__create_workqueue_key((name), (singlethread), (freezeable), NULL, NULL)
#endif
#define create_workqueue(name) __create_workqueue((name), 0, 0)
#define create_freezeable_workqueue(name) __create_workqueue((name), 1, 1)
#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0)
extern void destroy_workqueue(struct workqueue_struct *wq);
extern int queue_work(struct workqueue_struct *wq, struct work_struct *work);
extern int queue_work_on(int cpu, struct workqueue_struct *wq,
struct work_struct *work);
extern int queue_delayed_work(struct workqueue_struct *wq,
struct delayed_work *work, unsigned long delay);
extern int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *work, unsigned long delay);
extern void flush_workqueue(struct workqueue_struct *wq);
extern void flush_scheduled_work(void);
extern int schedule_work(struct work_struct *work);
extern int schedule_work_on(int cpu, struct work_struct *work);
extern int schedule_delayed_work(struct delayed_work *work, unsigned long delay);
extern int schedule_delayed_work_on(int cpu, struct delayed_work *work,
unsigned long delay);
extern int schedule_on_each_cpu(work_func_t func);
extern int current_is_keventd(void);
extern int keventd_up(void);
extern void init_workqueues(void);
int execute_in_process_context(work_func_t fn, struct execute_work *);
extern int flush_work(struct work_struct *work);
extern int cancel_work_sync(struct work_struct *work);
/*
* Kill off a pending schedule_delayed_work(). Note that the work callback
* function may still be running on return from cancel_delayed_work(), unless
* it returns 1 and the work doesn't re-arm itself. Run flush_workqueue() or
* cancel_work_sync() to wait on it.
*/
static inline int cancel_delayed_work(struct delayed_work *work)
{
int ret;
ret = del_timer_sync(&work->timer);
if (ret)
work_clear_pending(&work->work);
return ret;
}
extern int cancel_delayed_work_sync(struct delayed_work *work);
/* Obsolete. use cancel_delayed_work_sync() */
static inline
void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
struct delayed_work *work)
{
cancel_delayed_work_sync(work);
}
/* Obsolete. use cancel_delayed_work_sync() */
static inline
void cancel_rearming_delayed_work(struct delayed_work *work)
{
cancel_delayed_work_sync(work);
}
#endif