diff options
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/kernel/time.c | 48 |
1 files changed, 34 insertions, 14 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 2a7ddc57937..86f7e3d154d 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -283,9 +283,9 @@ static inline void update_gtod(u64 new_tb_stamp, u64 new_stamp_xsec, * the two values of tb_update_count match and are even then the * tb_to_xs and stamp_xsec values are consistent. If not, then it * loops back and reads them again until this criteria is met. + * We expect the caller to have done the first increment of + * vdso_data->tb_update_count already. */ - ++(vdso_data->tb_update_count); - smp_wmb(); vdso_data->tb_orig_stamp = new_tb_stamp; vdso_data->stamp_xsec = new_stamp_xsec; vdso_data->tb_to_xs = new_tb_to_xs; @@ -310,20 +310,15 @@ static __inline__ void timer_recalc_offset(u64 cur_tb) unsigned long offset; u64 new_stamp_xsec; u64 tlen, t2x; + u64 tb, xsec_old, xsec_new; + struct gettimeofday_vars *varp; if (__USE_RTC()) return; tlen = current_tick_length(); offset = cur_tb - do_gtod.varp->tb_orig_stamp; - if (tlen == last_tick_len && offset < 0x80000000u) { - /* check that we're still in sync; if not, resync */ - struct timeval tv; - __do_gettimeofday(&tv, cur_tb); - if (tv.tv_sec <= xtime.tv_sec && - (tv.tv_sec < xtime.tv_sec || - tv.tv_usec * 1000 <= xtime.tv_nsec)) - return; - } + if (tlen == last_tick_len && offset < 0x80000000u) + return; if (tlen != last_tick_len) { t2x = mulhdu(tlen << TICKLEN_SHIFT, ticklen_to_xs); last_tick_len = tlen; @@ -332,6 +327,21 @@ static __inline__ void timer_recalc_offset(u64 cur_tb) new_stamp_xsec = (u64) xtime.tv_nsec * XSEC_PER_SEC; do_div(new_stamp_xsec, 1000000000); new_stamp_xsec += (u64) xtime.tv_sec * XSEC_PER_SEC; + + ++vdso_data->tb_update_count; + smp_mb(); + + /* + * Make sure time doesn't go backwards for userspace gettimeofday. + */ + tb = get_tb(); + varp = do_gtod.varp; + xsec_old = mulhdu(tb - varp->tb_orig_stamp, varp->tb_to_xs) + + varp->stamp_xsec; + xsec_new = mulhdu(tb - cur_tb, t2x) + new_stamp_xsec; + if (xsec_new < xsec_old) + new_stamp_xsec += xsec_old - xsec_new; + update_gtod(cur_tb, new_stamp_xsec, t2x); } @@ -564,6 +574,10 @@ int do_settimeofday(struct timespec *tv) } #endif + /* Make userspace gettimeofday spin until we're done. */ + ++vdso_data->tb_update_count; + smp_mb(); + /* * Subtract off the number of nanoseconds since the * beginning of the last tick. @@ -724,10 +738,16 @@ void __init time_init(void) * It is computed as: * ticklen_to_xs = 2^N / (tb_ticks_per_jiffy * 1e9) * where N = 64 + 20 - TICKLEN_SCALE - TICKLEN_SHIFT - * so as to give the result as a 0.64 fixed-point fraction. + * which turns out to be N = 51 - SHIFT_HZ. + * This gives the result as a 0.64 fixed-point fraction. + * That value is reduced by an offset amounting to 1 xsec per + * 2^31 timebase ticks to avoid problems with time going backwards + * by 1 xsec when we do timer_recalc_offset due to losing the + * fractional xsec. That offset is equal to ppc_tb_freq/2^51 + * since there are 2^20 xsec in a second. */ - div128_by_32(1ULL << (64 + 20 - TICKLEN_SCALE - TICKLEN_SHIFT), 0, - tb_ticks_per_jiffy, &res); + div128_by_32((1ULL << 51) - ppc_tb_freq, 0, + tb_ticks_per_jiffy << SHIFT_HZ, &res); div128_by_32(res.result_high, res.result_low, NSEC_PER_SEC, &res); ticklen_to_xs = res.result_low; |