[deliverable/linux.git] / arch / x86 / include / asm / preempt.h

#ifndef __ASM_PREEMPT_H
#define __ASM_PREEMPT_H

#include <asm/rmwcc.h>
#include <asm/percpu.h>
#include <linux/thread_info.h>

DECLARE_PER_CPU(int, __preempt_count);

/*
 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
 * that a decrement hitting 0 means we can and should reschedule.
 */
#define PREEMPT_ENABLED	(0 + PREEMPT_NEED_RESCHED)

/*
 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
 * that think a non-zero value indicates we cannot preempt.
 */
static __always_inline int preempt_count(void)
{
	return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
}

static __always_inline void preempt_count_set(int pc)
{
	raw_cpu_write_4(__preempt_count, pc);
}

/*
 * must be macros to avoid header recursion hell
 */
#define task_preempt_count(p) \
	(task_thread_info(p)->saved_preempt_count & ~PREEMPT_NEED_RESCHED)

#define init_task_preempt_count(p) do { \
	task_thread_info(p)->saved_preempt_count = PREEMPT_DISABLED; \
} while (0)

#define init_idle_preempt_count(p, cpu) do { \
	task_thread_info(p)->saved_preempt_count = PREEMPT_ENABLED; \
	per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
} while (0)

/*
 * We fold the NEED_RESCHED bit into the preempt count such that
 * preempt_enable() can decrement and test for needing to reschedule with a
 * single instruction.
 *
 * We invert the actual bit, so that when the decrement hits 0 we know we both
 * need to resched (the bit is cleared) and can resched (no preempt count).
 */

static __always_inline void set_preempt_need_resched(void)
{
	raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
}

static __always_inline void clear_preempt_need_resched(void)
{
	raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
}

static __always_inline bool test_preempt_need_resched(void)
{
	return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
}

/*
 * The various preempt_count add/sub methods
 */

static __always_inline void __preempt_count_add(int val)
{
	raw_cpu_add_4(__preempt_count, val);
}

static __always_inline void __preempt_count_sub(int val)
{
	raw_cpu_add_4(__preempt_count, -val);
}

/*
 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
 * a decrement which hits zero means we have no preempt_count and should
 * reschedule.
 */
static __always_inline bool __preempt_count_dec_and_test(void)
{
	GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");
}

/*
 * Returns true when we need to resched and can (barring IRQ state).
 */
static __always_inline bool should_resched(void)
{
	return unlikely(!raw_cpu_read_4(__preempt_count));
}

#ifdef CONFIG_PREEMPT
  extern asmlinkage void ___preempt_schedule(void);
# define __preempt_schedule() asm ("call ___preempt_schedule")
  extern asmlinkage void preempt_schedule(void);
# ifdef CONFIG_CONTEXT_TRACKING
    extern asmlinkage void ___preempt_schedule_context(void);
#   define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
# endif
#endif

#endif /* __ASM_PREEMPT_H */
Commit	Line	Data
c2daa3be PZ	1	#ifndef __ASM_PREEMPT_H
	2	#define __ASM_PREEMPT_H
	3
	4	#include <asm/rmwcc.h>
	5	#include <asm/percpu.h>
	6	#include <linux/thread_info.h>
	7
	8	DECLARE_PER_CPU(int, __preempt_count);
	9
ba1f14fb PZ	10	/*
	11	* We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
	12	* that a decrement hitting 0 means we can and should reschedule.
	13	*/
	14	#define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
	15
c2daa3be PZ	16	/*
	17	* We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
	18	* that think a non-zero value indicates we cannot preempt.
	19	*/
	20	static __always_inline int preempt_count(void)
	21	{
b3ca1c10	22	return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
c2daa3be PZ	23	}
	24
	25	static __always_inline void preempt_count_set(int pc)
	26	{
b3ca1c10	27	raw_cpu_write_4(__preempt_count, pc);
c2daa3be PZ	28	}
	29
	30	/*
	31	* must be macros to avoid header recursion hell
	32	*/
	33	#define task_preempt_count(p) \
	34	(task_thread_info(p)->saved_preempt_count & ~PREEMPT_NEED_RESCHED)
	35
	36	#define init_task_preempt_count(p) do { \
	37	task_thread_info(p)->saved_preempt_count = PREEMPT_DISABLED; \
	38	} while (0)
	39
	40	#define init_idle_preempt_count(p, cpu) do { \
	41	task_thread_info(p)->saved_preempt_count = PREEMPT_ENABLED; \
	42	per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
	43	} while (0)
	44
	45	/*
	46	* We fold the NEED_RESCHED bit into the preempt count such that
	47	* preempt_enable() can decrement and test for needing to reschedule with a
	48	* single instruction.
	49	*
	50	* We invert the actual bit, so that when the decrement hits 0 we know we both
	51	* need to resched (the bit is cleared) and can resched (no preempt count).
	52	*/
	53
	54	static __always_inline void set_preempt_need_resched(void)
	55	{
b3ca1c10	56	raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
c2daa3be PZ	57	}
	58
	59	static __always_inline void clear_preempt_need_resched(void)
	60	{
b3ca1c10	61	raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
c2daa3be PZ	62	}
	63
	64	static __always_inline bool test_preempt_need_resched(void)
	65	{
b3ca1c10	66	return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
c2daa3be PZ	67	}
	68
	69	/*
	70	* The various preempt_count add/sub methods
	71	*/
	72
	73	static __always_inline void __preempt_count_add(int val)
	74	{
b3ca1c10	75	raw_cpu_add_4(__preempt_count, val);
c2daa3be PZ	76	}
	77
	78	static __always_inline void __preempt_count_sub(int val)
	79	{
b3ca1c10	80	raw_cpu_add_4(__preempt_count, -val);
c2daa3be PZ	81	}
c2daa3be PZ	82
ba1f14fb PZ	83	/*
	84	* Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
	85	* a decrement which hits zero means we have no preempt_count and should
	86	* reschedule.
	87	*/
c2daa3be PZ	88	static __always_inline bool __preempt_count_dec_and_test(void)
	89	{
	90	GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");
	91	}
	92
c2daa3be PZ	93	/*
	94	* Returns true when we need to resched and can (barring IRQ state).
	95	*/
	96	static __always_inline bool should_resched(void)
	97	{
b3ca1c10	98	return unlikely(!raw_cpu_read_4(__preempt_count));
c2daa3be PZ	99	}
c2daa3be PZ	100
1a338ac3 PZ	101	#ifdef CONFIG_PREEMPT
	102	extern asmlinkage void ___preempt_schedule(void);
	103	# define __preempt_schedule() asm ("call ___preempt_schedule")
	104	extern asmlinkage void preempt_schedule(void);
	105	# ifdef CONFIG_CONTEXT_TRACKING
	106	extern asmlinkage void ___preempt_schedule_context(void);
	107	# define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
	108	# endif
	109	#endif
	110
c2daa3be	111	#endif /* __ASM_PREEMPT_H */