kpriv/linux-hardened
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity
linux-hardened/include/linux/workqueue.h
Tejun Heo bbb68dfaba workqueue: mark a work item being canceled as such 
There can be two reasons try_to_grab_pending() can fail with -EAGAIN.
One is when someone else is queueing or deqeueing the work item.  With
the previous patches, it is guaranteed that PENDING and queued state
will soon agree making it safe to busy-retry in this case.

The other is if multiple __cancel_work_timer() invocations are racing
one another.  __cancel_work_timer() grabs PENDING and then waits for
running instances of the target work item on all CPUs while holding
PENDING and !queued.  try_to_grab_pending() invoked from another task
will keep returning -EAGAIN while the current owner is waiting.

Not distinguishing the two cases is okay because __cancel_work_timer()
is the only user of try_to_grab_pending() and it invokes
wait_on_work() whenever grabbing fails.  For the first case, busy
looping should be fine but wait_on_work() doesn't cause any critical
problem.  For the latter case, the new contender usually waits for the
same condition as the current owner, so no unnecessarily extended
busy-looping happens.  Combined, these make __cancel_work_timer()
technically correct even without irq protection while grabbing PENDING
or distinguishing the two different cases.

While the current code is technically correct, not distinguishing the
two cases makes it difficult to use try_to_grab_pending() for other
purposes than canceling because it's impossible to tell whether it's
safe to busy-retry grabbing.

This patch adds a mechanism to mark a work item being canceled.
try_to_grab_pending() now disables irq on success and returns -EAGAIN
to indicate that grabbing failed but PENDING and queued states are
gonna agree soon and it's safe to busy-loop.  It returns -ENOENT if
the work item is being canceled and it may stay PENDING && !queued for
arbitrary amount of time.

__cancel_work_timer() is modified to mark the work canceling with
WORK_OFFQ_CANCELING after grabbing PENDING, thus making
try_to_grab_pending() fail with -ENOENT instead of -EAGAIN.  Also, it
invokes wait_on_work() iff grabbing failed with -ENOENT.  This isn't
necessary for correctness but makes it consistent with other future
users of try_to_grab_pending().

v2: try_to_grab_pending() was testing preempt_count() to ensure that
    the caller has disabled preemption.  This triggers spuriously if
    !CONFIG_PREEMPT_COUNT.  Use preemptible() instead.  Reported by
    Fengguang Wu.

v3: Updated so that try_to_grab_pending() disables irq on success
    rather than requiring preemption disabled by the caller.  This
    makes busy-looping easier and will allow try_to_grap_pending() to
    be used from bh/irq contexts.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
2012-08-03 10:30:46 -07:00

469 lines
14 KiB
C
Raw Blame History

/*
* 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 <linux/threads.h>
#include <linux/atomic.h>
struct workqueue_struct;
struct work_struct;
typedef void (*work_func_t)(struct work_struct *work);
void delayed_work_timer_fn(unsigned long __data);
/*
* The first word is the work queue pointer and the flags rolled into
* one
*/
#define work_data_bits(work) ((unsigned long *)(&(work)->data))
enum {
WORK_STRUCT_PENDING_BIT = 0, /* work item is pending execution */
WORK_STRUCT_DELAYED_BIT = 1, /* work item is delayed */
WORK_STRUCT_CWQ_BIT = 2, /* data points to cwq */
WORK_STRUCT_LINKED_BIT = 3, /* next work is linked to this one */
#ifdef CONFIG_DEBUG_OBJECTS_WORK
WORK_STRUCT_STATIC_BIT = 4, /* static initializer (debugobjects) */
WORK_STRUCT_COLOR_SHIFT = 5, /* color for workqueue flushing */
#else
WORK_STRUCT_COLOR_SHIFT = 4, /* color for workqueue flushing */
#endif
WORK_STRUCT_COLOR_BITS = 4,
WORK_STRUCT_PENDING = 1 << WORK_STRUCT_PENDING_BIT,
WORK_STRUCT_DELAYED = 1 << WORK_STRUCT_DELAYED_BIT,
WORK_STRUCT_CWQ = 1 << WORK_STRUCT_CWQ_BIT,
WORK_STRUCT_LINKED = 1 << WORK_STRUCT_LINKED_BIT,
#ifdef CONFIG_DEBUG_OBJECTS_WORK
WORK_STRUCT_STATIC = 1 << WORK_STRUCT_STATIC_BIT,
#else
WORK_STRUCT_STATIC = 0,
#endif
/*
* The last color is no color used for works which don't
* participate in workqueue flushing.
*/
WORK_NR_COLORS = (1 << WORK_STRUCT_COLOR_BITS) - 1,
WORK_NO_COLOR = WORK_NR_COLORS,
/* special cpu IDs */
WORK_CPU_UNBOUND = NR_CPUS,
WORK_CPU_NONE = NR_CPUS + 1,
WORK_CPU_LAST = WORK_CPU_NONE,
/*
* Reserve 7 bits off of cwq pointer w/ debugobjects turned
* off. This makes cwqs aligned to 256 bytes and allows 15
* workqueue flush colors.
*/
WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT +
WORK_STRUCT_COLOR_BITS,
/* data contains off-queue information when !WORK_STRUCT_CWQ */
WORK_OFFQ_FLAG_BASE = WORK_STRUCT_FLAG_BITS,
WORK_OFFQ_CANCELING = (1 << WORK_OFFQ_FLAG_BASE),
WORK_OFFQ_FLAG_BITS = 1,
WORK_OFFQ_CPU_SHIFT = WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,
/* convenience constants */
WORK_STRUCT_FLAG_MASK = (1UL << WORK_STRUCT_FLAG_BITS) - 1,
WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
WORK_STRUCT_NO_CPU = (unsigned long)WORK_CPU_NONE << WORK_OFFQ_CPU_SHIFT,
/* bit mask for work_busy() return values */
WORK_BUSY_PENDING = 1 << 0,
WORK_BUSY_RUNNING = 1 << 1,
};
struct work_struct {
atomic_long_t data;
struct list_head entry;
work_func_t func;
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
};
#define WORK_DATA_INIT() ATOMIC_LONG_INIT(WORK_STRUCT_NO_CPU)
#define WORK_DATA_STATIC_INIT() \
ATOMIC_LONG_INIT(WORK_STRUCT_NO_CPU | WORK_STRUCT_STATIC)
struct delayed_work {
struct work_struct work;
struct timer_list timer;
};
static inline struct delayed_work *to_delayed_work(struct work_struct *work)
{
return container_of(work, struct delayed_work, work);
}
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_STATIC_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(delayed_work_timer_fn, \
0, (unsigned long)&(n)), \
}
#define __DEFERRED_WORK_INITIALIZER(n, f) { \
.work = __WORK_INITIALIZER((n).work, (f)), \
.timer = TIMER_DEFERRED_INITIALIZER(delayed_work_timer_fn, \
0, (unsigned long)&(n)), \
}
#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)
#define DECLARE_DEFERRED_WORK(n, f) \
struct delayed_work n = __DEFERRED_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))
#ifdef CONFIG_DEBUG_OBJECTS_WORK
extern void __init_work(struct work_struct *work, int onstack);
extern void destroy_work_on_stack(struct work_struct *work);
static inline unsigned int work_static(struct work_struct *work)
{
return *work_data_bits(work) & WORK_STRUCT_STATIC;
}
#else
static inline void __init_work(struct work_struct *work, int onstack) { }
static inline void destroy_work_on_stack(struct work_struct *work) { }
static inline unsigned int work_static(struct work_struct *work) { return 0; }
#endif
/*
* initialize all of a work item in one go
*
* NOTE! No point in using "atomic_long_set()": using a direct
* assignment of the work data initializer allows the compiler
* to generate better code.
*/
#ifdef CONFIG_LOCKDEP
#define __INIT_WORK(_work, _func, _onstack) \
do { \
static struct lock_class_key __key; \
\
__init_work((_work), _onstack); \
(_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, _onstack) \
do { \
__init_work((_work), _onstack); \
(_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
INIT_LIST_HEAD(&(_work)->entry); \
PREPARE_WORK((_work), (_func)); \
} while (0)
#endif
#define INIT_WORK(_work, _func) \
do { \
__INIT_WORK((_work), (_func), 0); \
} while (0)
#define INIT_WORK_ONSTACK(_work, _func) \
do { \
__INIT_WORK((_work), (_func), 1); \
} while (0)
#define INIT_DELAYED_WORK(_work, _func) \
do { \
INIT_WORK(&(_work)->work, (_func)); \
init_timer(&(_work)->timer); \
(_work)->timer.function = delayed_work_timer_fn;\
(_work)->timer.data = (unsigned long)(_work); \
} while (0)
#define INIT_DELAYED_WORK_ONSTACK(_work, _func) \
do { \
INIT_WORK_ONSTACK(&(_work)->work, (_func)); \
init_timer_on_stack(&(_work)->timer); \
(_work)->timer.function = delayed_work_timer_fn;\
(_work)->timer.data = (unsigned long)(_work); \
} while (0)
#define INIT_DELAYED_WORK_DEFERRABLE(_work, _func) \
do { \
INIT_WORK(&(_work)->work, (_func)); \
init_timer_deferrable(&(_work)->timer); \
(_work)->timer.function = delayed_work_timer_fn;\
(_work)->timer.data = (unsigned long)(_work); \
} 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_BIT, 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_BIT, work_data_bits(work))
/*
* Workqueue flags and constants. For details, please refer to
* Documentation/workqueue.txt.
*/
enum {
WQ_NON_REENTRANT = 1 << 0, /* guarantee non-reentrance */
WQ_UNBOUND = 1 << 1, /* not bound to any cpu */
WQ_FREEZABLE = 1 << 2, /* freeze during suspend */
WQ_MEM_RECLAIM = 1 << 3, /* may be used for memory reclaim */
WQ_HIGHPRI = 1 << 4, /* high priority */
WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */
WQ_DRAINING = 1 << 6, /* internal: workqueue is draining */
WQ_RESCUER = 1 << 7, /* internal: workqueue has rescuer */
WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */
WQ_DFL_ACTIVE = WQ_MAX_ACTIVE / 2,
};
/* unbound wq's aren't per-cpu, scale max_active according to #cpus */
#define WQ_UNBOUND_MAX_ACTIVE \
max_t(int, WQ_MAX_ACTIVE, num_possible_cpus() * WQ_MAX_UNBOUND_PER_CPU)
/*
* System-wide workqueues which are always present.
*
* system_wq is the one used by schedule[_delayed]_work[_on]().
* Multi-CPU multi-threaded. There are users which expect relatively
* short queue flush time. Don't queue works which can run for too
* long.
*
* system_long_wq is similar to system_wq but may host long running
* works. Queue flushing might take relatively long.
*
* system_nrt_wq is non-reentrant and guarantees that any given work
* item is never executed in parallel by multiple CPUs. Queue
* flushing might take relatively long.
*
* system_unbound_wq is unbound workqueue. Workers are not bound to
* any specific CPU, not concurrency managed, and all queued works are
* executed immediately as long as max_active limit is not reached and
* resources are available.
*
* system_freezable_wq is equivalent to system_wq except that it's
* freezable.
*
* system_nrt_freezable_wq is equivalent to system_nrt_wq except that
* it's freezable.
*/
extern struct workqueue_struct *system_wq;
extern struct workqueue_struct *system_long_wq;
extern struct workqueue_struct *system_nrt_wq;
extern struct workqueue_struct *system_unbound_wq;
extern struct workqueue_struct *system_freezable_wq;
extern struct workqueue_struct *system_nrt_freezable_wq;
extern struct workqueue_struct *
__alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active,
struct lock_class_key *key, const char *lock_name, ...) __printf(1, 6);
/**
* alloc_workqueue - allocate a workqueue
* @fmt: printf format for the name of the workqueue
* @flags: WQ_* flags
* @max_active: max in-flight work items, 0 for default
* @args: args for @fmt
*
* Allocate a workqueue with the specified parameters. For detailed
* information on WQ_* flags, please refer to Documentation/workqueue.txt.
*
* The __lock_name macro dance is to guarantee that single lock_class_key
* doesn't end up with different namesm, which isn't allowed by lockdep.
*
* RETURNS:
* Pointer to the allocated workqueue on success, %NULL on failure.
*/
#ifdef CONFIG_LOCKDEP
#define alloc_workqueue(fmt, flags, max_active, args...) \
({ \
static struct lock_class_key __key; \
const char *__lock_name; \
\
if (__builtin_constant_p(fmt)) \
__lock_name = (fmt); \
else \
__lock_name = #fmt; \
\
__alloc_workqueue_key((fmt), (flags), (max_active), \
&__key, __lock_name, ##args); \
})
#else
#define alloc_workqueue(fmt, flags, max_active, args...) \
__alloc_workqueue_key((fmt), (flags), (max_active), \
NULL, NULL, ##args)
#endif
/**
* alloc_ordered_workqueue - allocate an ordered workqueue
* @fmt: printf format for the name of the workqueue
* @flags: WQ_* flags (only WQ_FREEZABLE and WQ_MEM_RECLAIM are meaningful)
* @args: args for @fmt
*
* Allocate an ordered workqueue. An ordered workqueue executes at
* most one work item at any given time in the queued order. They are
* implemented as unbound workqueues with @max_active of one.
*
* RETURNS:
* Pointer to the allocated workqueue on success, %NULL on failure.
*/
#define alloc_ordered_workqueue(fmt, flags, args...) \
alloc_workqueue(fmt, WQ_UNBOUND | (flags), 1, ##args)
#define create_workqueue(name) \
alloc_workqueue((name), WQ_MEM_RECLAIM, 1)
#define create_freezable_workqueue(name) \
alloc_workqueue((name), WQ_FREEZABLE | WQ_UNBOUND | WQ_MEM_RECLAIM, 1)
#define create_singlethread_workqueue(name) \
alloc_workqueue((name), WQ_UNBOUND | WQ_MEM_RECLAIM, 1)
extern void destroy_workqueue(struct workqueue_struct *wq);
extern bool queue_work_on(int cpu, struct workqueue_struct *wq,
struct work_struct *work);
extern bool queue_work(struct workqueue_struct *wq, struct work_struct *work);
extern bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *work, unsigned long delay);
extern bool queue_delayed_work(struct workqueue_struct *wq,
struct delayed_work *work, unsigned long delay);
extern void flush_workqueue(struct workqueue_struct *wq);
extern void drain_workqueue(struct workqueue_struct *wq);
extern void flush_scheduled_work(void);
extern bool schedule_work_on(int cpu, struct work_struct *work);
extern bool schedule_work(struct work_struct *work);
extern bool schedule_delayed_work_on(int cpu, struct delayed_work *work,
unsigned long delay);
extern bool schedule_delayed_work(struct delayed_work *work,
unsigned long delay);
extern int schedule_on_each_cpu(work_func_t func);
extern int keventd_up(void);
int execute_in_process_context(work_func_t fn, struct execute_work *);
extern bool flush_work(struct work_struct *work);
extern bool flush_work_sync(struct work_struct *work);
extern bool cancel_work_sync(struct work_struct *work);
extern bool flush_delayed_work(struct delayed_work *dwork);
extern bool flush_delayed_work_sync(struct delayed_work *work);
extern bool cancel_delayed_work_sync(struct delayed_work *dwork);
extern void workqueue_set_max_active(struct workqueue_struct *wq,
int max_active);
extern bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq);
extern unsigned int work_cpu(struct work_struct *work);
extern unsigned int work_busy(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 bool cancel_delayed_work(struct delayed_work *work)
{
bool ret;
ret = del_timer_sync(&work->timer);
if (ret)
work_clear_pending(&work->work);
return ret;
}
/*
* Like above, but uses del_timer() instead of del_timer_sync(). This means,
* if it returns 0 the timer function may be running and the queueing is in
* progress.
*/
static inline bool __cancel_delayed_work(struct delayed_work *work)
{
bool ret;
ret = del_timer(&work->timer);
if (ret)
work_clear_pending(&work->work);
return ret;
}
#ifndef CONFIG_SMP
static inline long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
{
return fn(arg);
}
#else
long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg);
#endif /* CONFIG_SMP */
#ifdef CONFIG_FREEZER
extern void freeze_workqueues_begin(void);
extern bool freeze_workqueues_busy(void);
extern void thaw_workqueues(void);
#endif /* CONFIG_FREEZER */
#endif
Reference in a new issue View git blame Copy permalink