tile: switch to using seqlocks for the vDSO time code

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

diff --git a/arch/tile/include/asm/vdso.h b/arch/tile/include/asm/vdso.h
index 9f6a78d..d64b0d5 100644 (file)
--- a/arch/tile/include/asm/vdso.h
+++ b/arch/tile/include/asm/vdso.h
@@ -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             */

diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c
index d8fbc28..2fe8323 100644 (file)
--- a/arch/tile/kernel/time.c
+++ b/arch/tile/kernel/time.c
@@ -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);
 }

diff --git a/arch/tile/kernel/vdso/vgettimeofday.c b/arch/tile/kernel/vdso/vgettimeofday.c
index e933fb9..7cff8fb 100644 (file)
--- a/arch/tile/kernel/vdso/vgettimeofday.c
+++ b/arch/tile/kernel/vdso/vgettimeofday.c
@@ -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;