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Commit dd6414b5 authored by Phil Carmody's avatar Phil Carmody Committed by Thomas Gleixner
Browse files

timer: Permit statically-declared work with deferrable timers 



Currently, you have to just define a delayed_work uninitialised, and then
initialise it before first use.  That's a tad clumsy.  At risk of playing
mind-games with the compiler, fooling it into doing pointer arithmetic
with compile-time-constants, this lets clients properly initialise delayed
work with deferrable timers statically.

This patch was inspired by the issues which lead Artem Bityutskiy to
commit 8eab945c ("sunrpc: make the cache cleaner workqueue
deferrable").

Signed-off-by: default avatarPhil Carmody <ext-phil.2.carmody@nokia.com>
Acked-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 2bf1c05e

include/linux/timer.h

+25 −0
Original line number Diff line number Diff line
@@ -48,6 +48,18 @@ extern struct tvec_base boot_tvec_bases; 
#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn)

#endif



/*

 * Note that all tvec_bases are 2 byte aligned and lower bit of

 * base in timer_list is guaranteed to be zero. Use the LSB to

 * indicate whether the timer is deferrable.

 *

 * A deferrable timer will work normally when the system is busy, but

 * will not cause a CPU to come out of idle just to service it; instead,

 * the timer will be serviced when the CPU eventually wakes up with a

 * subsequent non-deferrable timer.

 */

#define TBASE_DEFERRABLE_FLAG		(0x1)



#define TIMER_INITIALIZER(_function, _expires, _data) {		\

		.entry = { .prev = TIMER_ENTRY_STATIC },	\

		.function = (_function),			\
@@ -59,6 +71,19 @@ extern struct tvec_base boot_tvec_bases; 
			__FILE__ ":" __stringify(__LINE__))	\

	}



#define TBASE_MAKE_DEFERRED(ptr) ((struct tvec_base *)		\

		  ((unsigned char *)(ptr) + TBASE_DEFERRABLE_FLAG))



#define TIMER_DEFERRED_INITIALIZER(_function, _expires, _data) {\

		.entry = { .prev = TIMER_ENTRY_STATIC },	\

		.function = (_function),			\

		.expires = (_expires),				\

		.data = (_data),				\

		.base = TBASE_MAKE_DEFERRED(&boot_tvec_bases),	\

		__TIMER_LOCKDEP_MAP_INITIALIZER(		\

			__FILE__ ":" __stringify(__LINE__))	\

	}



#define DEFINE_TIMER(_name, _function, _expires, _data)		\

	struct timer_list _name =				\

		TIMER_INITIALIZER(_function, _expires, _data)

include/linux/workqueue.h

+8 −0
Original line number Diff line number Diff line
@@ -127,12 +127,20 @@ struct execute_work { 
	.timer = TIMER_INITIALIZER(NULL, 0, 0),			\

	}



#define __DEFERRED_WORK_INITIALIZER(n, f) {			\

	.work = __WORK_INITIALIZER((n).work, (f)),		\

	.timer = TIMER_DEFERRED_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)



#define DECLARE_DEFERRED_WORK(n, f)				\

	struct delayed_work n = __DEFERRED_WORK_INITIALIZER(n, f)



/*

 * initialize a work item's function pointer

 */

kernel/timer.c

+1 −14
Original line number Diff line number Diff line
@@ -88,18 +88,6 @@ struct tvec_base boot_tvec_bases; 
EXPORT_SYMBOL(boot_tvec_bases);

static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;



/*

 * Note that all tvec_bases are 2 byte aligned and lower bit of

 * base in timer_list is guaranteed to be zero. Use the LSB to

 * indicate whether the timer is deferrable.

 *

 * A deferrable timer will work normally when the system is busy, but

 * will not cause a CPU to come out of idle just to service it; instead,

 * the timer will be serviced when the CPU eventually wakes up with a

 * subsequent non-deferrable timer.

 */

#define TBASE_DEFERRABLE_FLAG		(0x1)



/* Functions below help us manage 'deferrable' flag */

static inline unsigned int tbase_get_deferrable(struct tvec_base *base)

{
@@ -113,8 +101,7 @@ static inline struct tvec_base *tbase_get_base(struct tvec_base *base) 


static inline void timer_set_deferrable(struct timer_list *timer)

{

	timer->base = ((struct tvec_base *)((unsigned long)(timer->base) |

				       TBASE_DEFERRABLE_FLAG));

	timer->base = TBASE_MAKE_DEFERRED(timer->base);

}



static inline void