workqueue: remove PREPARE_[DELAYED_]WORK() (f073f922) · Commits · 戴 / test

Peter Hurley noticed that since ("workqueue: consider work function when searching for busy work items"), a work item which gets assigned a different work function would break out of the non-reentrancy guarantee as workqueue would consider it a different work item. This is fragile and extremely subtle. PREPARE_[DELAYED_]WORK() have never been used widely and its semantics has always been somewhat iffy. If the work item is known not to be on queue when PREPARE_WORK() is called, there's no difference from using INIT_WORK(). If the work item may be queued at the time of PREPARE_WORK(), we can't really tell whether the old or new function will be executed the next time. We really don't want this level of subtlety in workqueue interface for such marginal use cases. The previous patches converted all existing users away from PREPARE_[DELAYED_]WORK(). Let's remove them. Signed-off-by:

Tejun Heo <tj@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Link: http://lkml.kernel.org/g/1392493119-9277-1-git-send-email-peter@hurleysoftware.com

include/linux/workqueue.h

+2 −13

Original line number	Diff line number	Diff line
		@@ -177,17 +177,6 @@ struct execute_work {
		#define DECLARE_DEFERRABLE_WORK(n, f) \
		struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f, TIMER_DEFERRABLE)

		/*
		* 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);
		@@ -217,7 +206,7 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
		(_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)); \
		(_work)->func = (_func); \
		} while (0)
		#else
		#define __INIT_WORK(_work, _func, _onstack) \
		@@ -225,7 +214,7 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
		__init_work((_work), _onstack); \
		(_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
		INIT_LIST_HEAD(&(_work)->entry); \
		PREPARE_WORK((_work), (_func)); \
		(_work)->func = (_func); \
		} while (0)
		#endif

Admin message