[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 init_task_preempt_count(p) do { } while (0)

#define init_idle_preempt_count(p, cpu) do { \
	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(int preempt_offset)
{
	return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
}

#ifdef CONFIG_PREEMPT
  extern asmlinkage void ___preempt_schedule(void);
# define __preempt_schedule() asm ("call ___preempt_schedule")
  extern asmlinkage void preempt_schedule(void);
  extern asmlinkage void ___preempt_schedule_notrace(void);
# define __preempt_schedule_notrace() asm ("call ___preempt_schedule_notrace")
  extern asmlinkage void preempt_schedule_notrace(void);
#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	*/
d87b7a33	33	#define init_task_preempt_count(p) do { } while (0)
c2daa3be PZ	34
c2daa3be PZ	35	#define init_idle_preempt_count(p, cpu) do { \
c2daa3be PZ	36	per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
	37	} while (0)
	38
	39	/*
	40	* We fold the NEED_RESCHED bit into the preempt count such that
	41	* preempt_enable() can decrement and test for needing to reschedule with a
	42	* single instruction.
	43	*
	44	* We invert the actual bit, so that when the decrement hits 0 we know we both
	45	* need to resched (the bit is cleared) and can resched (no preempt count).
	46	*/
	47
	48	static __always_inline void set_preempt_need_resched(void)
	49	{
b3ca1c10	50	raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
c2daa3be PZ	51	}
	52
	53	static __always_inline void clear_preempt_need_resched(void)
	54	{
b3ca1c10	55	raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
c2daa3be PZ	56	}
	57
	58	static __always_inline bool test_preempt_need_resched(void)
	59	{
b3ca1c10	60	return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
c2daa3be PZ	61	}
	62
	63	/*
	64	* The various preempt_count add/sub methods
	65	*/
	66
	67	static __always_inline void __preempt_count_add(int val)
	68	{
b3ca1c10	69	raw_cpu_add_4(__preempt_count, val);
c2daa3be PZ	70	}
	71
	72	static __always_inline void __preempt_count_sub(int val)
	73	{
b3ca1c10	74	raw_cpu_add_4(__preempt_count, -val);
c2daa3be PZ	75	}
c2daa3be PZ	76
ba1f14fb PZ	77	/*
	78	* Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
	79	* a decrement which hits zero means we have no preempt_count and should
	80	* reschedule.
	81	*/
c2daa3be PZ	82	static __always_inline bool __preempt_count_dec_and_test(void)
	83	{
	84	GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");
	85	}
	86
c2daa3be PZ	87	/*
	88	* Returns true when we need to resched and can (barring IRQ state).
	89	*/
fe32d3cd	90	static __always_inline bool should_resched(int preempt_offset)
c2daa3be	91	{
fe32d3cd	92	return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
c2daa3be PZ	93	}
c2daa3be PZ	94
1a338ac3 PZ	95	#ifdef CONFIG_PREEMPT
	96	extern asmlinkage void ___preempt_schedule(void);
	97	# define __preempt_schedule() asm ("call ___preempt_schedule")
	98	extern asmlinkage void preempt_schedule(void);
4eaca0a8 FW	99	extern asmlinkage void ___preempt_schedule_notrace(void);
	100	# define __preempt_schedule_notrace() asm ("call ___preempt_schedule_notrace")
	101	extern asmlinkage void preempt_schedule_notrace(void);
1a338ac3 PZ	102	#endif
1a338ac3 PZ	103
c2daa3be	104	#endif /* __ASM_PREEMPT_H */