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Commit 94fb1afb authored by Chris Metcalf's avatar Chris Metcalf
Browse files

tile: switch to using seqlocks for the vDSO time code 



Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
parent bceb7efa

arch/tile/include/asm/vdso.h

+3 −2
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#ifndef __TILE_VDSO_H__

#define __TILE_VDSO_H__



#include <linux/seqlock.h>

#include <linux/types.h>



/*
@@ -26,8 +27,8 @@ 
 */



struct vdso_data {

	__u64 tz_update_count;  /* Timezone atomicity ctr             */

	__u64 tb_update_count;  /* Timebase atomicity ctr             */

	seqcount_t tz_seq;	/* Timezone seqlock                   */

	seqcount_t tb_seq;	/* Timebase seqlock                   */

	__u64 xtime_tod_stamp;  /* TOD clock for xtime                */

	__u64 xtime_clock_sec;  /* Kernel time second                 */

	__u64 xtime_clock_nsec; /* Kernel time nanosecond             */

arch/tile/kernel/time.c

+6 −10
Original line number Diff line number Diff line
@@ -249,13 +249,10 @@ cycles_t ns2cycles(unsigned long nsecs) 


void update_vsyscall_tz(void)

{

	/* Userspace gettimeofday will spin while this value is odd. */

	++vdso_data->tz_update_count;

	smp_wmb();

	write_seqcount_begin(&vdso_data->tz_seq);

	vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;

	vdso_data->tz_dsttime = sys_tz.tz_dsttime;

	smp_wmb();

	++vdso_data->tz_update_count;

	write_seqcount_end(&vdso_data->tz_seq);

}



void update_vsyscall(struct timekeeper *tk)
@@ -266,9 +263,8 @@ void update_vsyscall(struct timekeeper *tk) 
	if (clock != &cycle_counter_cs)

		return;



	/* Userspace gettimeofday will spin while this value is odd. */

	++vdso_data->tb_update_count;

	smp_wmb();

	write_seqcount_begin(&vdso_data->tb_seq);



	vdso_data->xtime_tod_stamp = tk->tkr.cycle_last;

	vdso_data->xtime_clock_sec = tk->xtime_sec;

	vdso_data->xtime_clock_nsec = tk->tkr.xtime_nsec;
@@ -276,6 +272,6 @@ void update_vsyscall(struct timekeeper *tk) 
	vdso_data->wtom_clock_nsec = wtm->tv_nsec;

	vdso_data->mult = tk->tkr.mult;

	vdso_data->shift = tk->tkr.shift;

	smp_wmb();

	++vdso_data->tb_update_count;



	write_seqcount_end(&vdso_data->tb_seq);

}

arch/tile/kernel/vdso/vgettimeofday.c

+15 −32
Original line number Diff line number Diff line
@@ -53,50 +53,33 @@ inline unsigned long get_datapage(void) 
int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)

{

	cycles_t cycles;

	unsigned long count, sec, ns;

	volatile struct vdso_data *vdso_data;

	unsigned count;

	unsigned long sec, ns;

	struct vdso_data *vdso = (struct vdso_data *)get_datapage();



	vdso_data = (struct vdso_data *)get_datapage();

	/* The use of the timezone is obsolete, normally tz is NULL. */

	if (unlikely(tz != NULL)) {

		while (1) {

			/* Spin until the update finish. */

			count = vdso_data->tz_update_count;

			if (count & 1)

				continue;



			tz->tz_minuteswest = vdso_data->tz_minuteswest;

			tz->tz_dsttime = vdso_data->tz_dsttime;



			/* Check whether updated, read again if so. */

			if (count == vdso_data->tz_update_count)

				break;

		}

		do {

			count = read_seqcount_begin(&vdso->tz_seq);

			tz->tz_minuteswest = vdso->tz_minuteswest;

			tz->tz_dsttime = vdso->tz_dsttime;

		} while (unlikely(read_seqcount_retry(&vdso->tz_seq, count)));

	}



	if (unlikely(tv == NULL))

		return 0;



	while (1) {

		/* Spin until the update finish. */

		count = vdso_data->tb_update_count;

		if (count & 1)

			continue;



		sec = vdso_data->xtime_clock_sec;

		cycles = get_cycles() - vdso_data->xtime_tod_stamp;

		ns = (cycles * vdso_data->mult) + vdso_data->xtime_clock_nsec;

		ns >>= vdso_data->shift;



	do {

		count = read_seqcount_begin(&vdso->tb_seq);

		sec = vdso->xtime_clock_sec;

		cycles = get_cycles() - vdso->xtime_tod_stamp;

		ns = (cycles * vdso->mult) + vdso->xtime_clock_nsec;

		ns >>= vdso->shift;

		if (ns >= NSEC_PER_SEC) {

			ns -= NSEC_PER_SEC;

			sec += 1;

		}



		/* Check whether updated, read again if so. */

		if (count == vdso_data->tb_update_count)

			break;

	}

	} while (unlikely(read_seqcount_retry(&vdso->tb_seq, count)));



	tv->tv_sec = sec;

	tv->tv_usec = ns / 1000;