sched_clock: Expose struct clock_read_data

#define LINUX_SCHED_CLOCK

#ifdef CONFIG_GENERIC_SCHED_CLOCK

/**

 * struct clock_read_data - data required to read from sched_clock()

 *

 * @epoch_ns:		sched_clock() value at last update

 * @epoch_cyc:		Clock cycle value at last update.

 * @sched_clock_mask:   Bitmask for two's complement subtraction of non 64bit

 *			clocks.

 * @read_sched_clock:	Current clock source (or dummy source when suspended).

 * @mult:		Multipler for scaled math conversion.

 * @shift:		Shift value for scaled math conversion.

 *

 * Care must be taken when updating this structure; it is read by

 * some very hot code paths. It occupies <=40 bytes and, when combined

 * with the seqcount used to synchronize access, comfortably fits into

 * a 64 byte cache line.

 */

struct clock_read_data {

	u64 epoch_ns;

	u64 epoch_cyc;

	u64 sched_clock_mask;

	u64 (*read_sched_clock)(void);

	u32 mult;

	u32 shift;

};

extern struct clock_read_data *sched_clock_read_begin(unsigned int *seq);

extern int sched_clock_read_retry(unsigned int seq);

extern void generic_sched_clock_init(void);

extern void sched_clock_register(u64 (*read)(void), int bits,

#include "timekeeping.h"

/**

 * struct clock_read_data - data required to read from sched_clock()

 *

 * @epoch_ns:		sched_clock() value at last update

 * @epoch_cyc:		Clock cycle value at last update.

 * @sched_clock_mask:   Bitmask for two's complement subtraction of non 64bit

 *			clocks.

 * @read_sched_clock:	Current clock source (or dummy source when suspended).

 * @mult:		Multipler for scaled math conversion.

 * @shift:		Shift value for scaled math conversion.

 *

 * Care must be taken when updating this structure; it is read by

 * some very hot code paths. It occupies <=40 bytes and, when combined

 * with the seqcount used to synchronize access, comfortably fits into

 * a 64 byte cache line.

 */

struct clock_read_data {

	u64 epoch_ns;

	u64 epoch_cyc;

	u64 sched_clock_mask;

	u64 (*read_sched_clock)(void);

	u32 mult;

	u32 shift;

};

/**

 * struct clock_data - all data needed for sched_clock() (including

 *                     registration of a new clock source)

	return (cyc * mult) >> shift;

}

struct clock_read_data *sched_clock_read_begin(unsigned int *seq)

{

	*seq = raw_read_seqcount(&cd.seq);

	return cd.read_data + (*seq & 1);

}

int sched_clock_read_retry(unsigned int seq)

{

	return read_seqcount_retry(&cd.seq, seq);

}

unsigned long long notrace sched_clock(void)

{

	u64 cyc, res;

	struct clock_read_data *rd;

	do {

		seq = raw_read_seqcount(&cd.seq);

		rd = cd.read_data + (seq & 1);

		rd = sched_clock_read_begin(&seq);

		cyc = (rd->read_sched_clock() - rd->epoch_cyc) &

		      rd->sched_clock_mask;

		res = rd->epoch_ns + cyc_to_ns(cyc, rd->mult, rd->shift);

	} while (read_seqcount_retry(&cd.seq, seq));

	} while (sched_clock_read_retry(seq));

	return res;

}