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tile: switch to using seqlocks for the vDSO time code

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Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
This commit is contained in:
Chris Metcalf 2014-10-02 10:48:12 -04:00
parent bceb7efa6a
commit 94fb1afbcb
3 changed files with 24 additions and 44 deletions
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5
arch/tile/include/asm/vdso.h
View File

@ -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 */

16
arch/tile/kernel/time.c
View File

@ -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);
}

47
arch/tile/kernel/vdso/vgettimeofday.c
View File

@ -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;