![Linus Torvalds](/assets/img/avatar_default.png)
On architectures where the atomicity of the bit operations is handled by
external means (ie a separate spinlock to protect concurrent accesses),
just doing a direct assignment on the workqueue data field (as done by
commit 4594bf159f
) can cause the
assignment to be lost due to lack of serialization with the bitops on
the same word.
So we need to serialize the assignment with the locks on those
architectures (notably older ARM chips, PA-RISC and sparc32).
So rather than using an "unsigned long", let's use "atomic_long_t",
which already has a safe assignment operation (atomic_long_set()) on
such architectures.
This requires that the atomic operations use the same atomicity locks as
the bit operations do, but that is largely the case anyway. Sparc32
will probably need fixing.
Architectures (including modern ARM with LL/SC) that implement sane
atomic operations for SMP won't see any of this matter.
Cc: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: David Miller <davem@davemloft.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Linux Arch Maintainers <linux-arch@vger.kernel.org>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
208 lines
6.3 KiB
C
208 lines
6.3 KiB
C
/*
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* workqueue.h --- work queue handling for Linux.
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*/
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#ifndef _LINUX_WORKQUEUE_H
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#define _LINUX_WORKQUEUE_H
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#include <linux/timer.h>
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#include <linux/linkage.h>
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#include <linux/bitops.h>
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#include <asm/atomic.h>
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struct workqueue_struct;
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struct work_struct;
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typedef void (*work_func_t)(struct work_struct *work);
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/*
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* The first word is the work queue pointer and the flags rolled into
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* one
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*/
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#define work_data_bits(work) ((unsigned long *)(&(work)->data))
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struct work_struct {
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atomic_long_t data;
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#define WORK_STRUCT_PENDING 0 /* T if work item pending execution */
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#define WORK_STRUCT_NOAUTOREL 1 /* F if work item automatically released on exec */
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#define WORK_STRUCT_FLAG_MASK (3UL)
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#define WORK_STRUCT_WQ_DATA_MASK (~WORK_STRUCT_FLAG_MASK)
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struct list_head entry;
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work_func_t func;
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};
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#define WORK_DATA_INIT(autorelease) \
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ATOMIC_LONG_INIT((autorelease) << WORK_STRUCT_NOAUTOREL)
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struct delayed_work {
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struct work_struct work;
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struct timer_list timer;
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};
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struct execute_work {
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struct work_struct work;
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};
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#define __WORK_INITIALIZER(n, f) { \
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.data = WORK_DATA_INIT(0), \
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.entry = { &(n).entry, &(n).entry }, \
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.func = (f), \
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}
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#define __WORK_INITIALIZER_NAR(n, f) { \
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.data = WORK_DATA_INIT(1), \
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.entry = { &(n).entry, &(n).entry }, \
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.func = (f), \
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}
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#define __DELAYED_WORK_INITIALIZER(n, f) { \
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.work = __WORK_INITIALIZER((n).work, (f)), \
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.timer = TIMER_INITIALIZER(NULL, 0, 0), \
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}
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#define __DELAYED_WORK_INITIALIZER_NAR(n, f) { \
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.work = __WORK_INITIALIZER_NAR((n).work, (f)), \
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.timer = TIMER_INITIALIZER(NULL, 0, 0), \
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}
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#define DECLARE_WORK(n, f) \
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struct work_struct n = __WORK_INITIALIZER(n, f)
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#define DECLARE_WORK_NAR(n, f) \
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struct work_struct n = __WORK_INITIALIZER_NAR(n, f)
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#define DECLARE_DELAYED_WORK(n, f) \
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struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f)
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#define DECLARE_DELAYED_WORK_NAR(n, f) \
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struct dwork_struct n = __DELAYED_WORK_INITIALIZER_NAR(n, f)
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/*
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* initialize a work item's function pointer
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*/
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#define PREPARE_WORK(_work, _func) \
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do { \
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(_work)->func = (_func); \
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} while (0)
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#define PREPARE_DELAYED_WORK(_work, _func) \
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PREPARE_WORK(&(_work)->work, (_func))
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/*
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* initialize all of a work item in one go
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*
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* NOTE! No point in using "atomic_long_set()": useing a direct
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* assignment of the work data initializer allows the compiler
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* to generate better code.
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*/
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#define INIT_WORK(_work, _func) \
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do { \
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(_work)->data = (atomic_long_t) WORK_DATA_INIT(0); \
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INIT_LIST_HEAD(&(_work)->entry); \
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PREPARE_WORK((_work), (_func)); \
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} while (0)
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#define INIT_WORK_NAR(_work, _func) \
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do { \
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(_work)->data = (atomic_long_t) WORK_DATA_INIT(1); \
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INIT_LIST_HEAD(&(_work)->entry); \
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PREPARE_WORK((_work), (_func)); \
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} while (0)
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#define INIT_DELAYED_WORK(_work, _func) \
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do { \
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INIT_WORK(&(_work)->work, (_func)); \
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init_timer(&(_work)->timer); \
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} while (0)
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#define INIT_DELAYED_WORK_NAR(_work, _func) \
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do { \
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INIT_WORK_NAR(&(_work)->work, (_func)); \
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init_timer(&(_work)->timer); \
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} while (0)
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/**
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* work_pending - Find out whether a work item is currently pending
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* @work: The work item in question
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*/
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#define work_pending(work) \
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test_bit(WORK_STRUCT_PENDING, work_data_bits(work))
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/**
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* delayed_work_pending - Find out whether a delayable work item is currently
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* pending
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* @work: The work item in question
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*/
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#define delayed_work_pending(w) \
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work_pending(&(w)->work)
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/**
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* work_release - Release a work item under execution
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* @work: The work item to release
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*
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* This is used to release a work item that has been initialised with automatic
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* release mode disabled (WORK_STRUCT_NOAUTOREL is set). This gives the work
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* function the opportunity to grab auxiliary data from the container of the
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* work_struct before clearing the pending bit as the work_struct may be
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* subject to deallocation the moment the pending bit is cleared.
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*
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* In such a case, this should be called in the work function after it has
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* fetched any data it may require from the containter of the work_struct.
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* After this function has been called, the work_struct may be scheduled for
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* further execution or it may be deallocated unless other precautions are
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* taken.
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*
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* This should also be used to release a delayed work item.
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*/
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#define work_release(work) \
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clear_bit(WORK_STRUCT_PENDING, work_data_bits(work))
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extern struct workqueue_struct *__create_workqueue(const char *name,
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int singlethread,
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int freezeable);
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#define create_workqueue(name) __create_workqueue((name), 0, 0)
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#define create_freezeable_workqueue(name) __create_workqueue((name), 0, 1)
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#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0)
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extern void destroy_workqueue(struct workqueue_struct *wq);
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extern int FASTCALL(queue_work(struct workqueue_struct *wq, struct work_struct *work));
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extern int FASTCALL(queue_delayed_work(struct workqueue_struct *wq, struct delayed_work *work, unsigned long delay));
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extern int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
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struct delayed_work *work, unsigned long delay);
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extern void FASTCALL(flush_workqueue(struct workqueue_struct *wq));
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extern int FASTCALL(schedule_work(struct work_struct *work));
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extern int FASTCALL(run_scheduled_work(struct work_struct *work));
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extern int FASTCALL(schedule_delayed_work(struct delayed_work *work, unsigned long delay));
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extern int schedule_delayed_work_on(int cpu, struct delayed_work *work, unsigned long delay);
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extern int schedule_on_each_cpu(work_func_t func);
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extern void flush_scheduled_work(void);
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extern int current_is_keventd(void);
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extern int keventd_up(void);
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extern void init_workqueues(void);
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void cancel_rearming_delayed_work(struct delayed_work *work);
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void cancel_rearming_delayed_workqueue(struct workqueue_struct *,
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struct delayed_work *);
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int execute_in_process_context(work_func_t fn, struct execute_work *);
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/*
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* Kill off a pending schedule_delayed_work(). Note that the work callback
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* function may still be running on return from cancel_delayed_work(). Run
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* flush_scheduled_work() to wait on it.
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*/
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static inline int cancel_delayed_work(struct delayed_work *work)
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{
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int ret;
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ret = del_timer_sync(&work->timer);
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if (ret)
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work_release(&work->work);
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return ret;
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}
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#endif
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