[PATCH] ALSA: seq_timer: use monotonic times internally
From: Arnd Bergmann
Date: Fri Jun 17 2016 - 11:09:24 EST
The sequencer client manager reports timestamps in units of unsigned
32-bit seconds/nanoseconds, but that does not suffer from the y2038
overflow because it stores only the delta since the 'last_update'
time was recorded.
However, the use of the do_gettimeofday() function is problematic
and we have to replace it to avoid the overflow on on 32-bit
architectures.
This uses 'struct timespec64' to record 'last_update', and changes
the code to use monotonic timestamps that do not suffer from leap
seconds and settimeofday updates.
As a side-effect, the code can now use the timespec64_sub() helper
and become more readable and also avoid a multiplication to convert
from microseconds to nanoseconds.
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
sound/core/seq/seq_timer.c | 23 +++++++++--------------
sound/core/seq/seq_timer.h | 2 +-
2 files changed, 10 insertions(+), 15 deletions(-)
diff --git a/sound/core/seq/seq_timer.c b/sound/core/seq/seq_timer.c
index 293104926098..dcc102813aef 100644
--- a/sound/core/seq/seq_timer.c
+++ b/sound/core/seq/seq_timer.c
@@ -165,7 +165,7 @@ static void snd_seq_timer_interrupt(struct snd_timer_instance *timeri,
snd_seq_timer_update_tick(&tmr->tick, resolution);
/* register actual time of this timer update */
- do_gettimeofday(&tmr->last_update);
+ ktime_get_ts64(&tmr->last_update);
spin_unlock_irqrestore(&tmr->lock, flags);
@@ -392,7 +392,7 @@ static int seq_timer_start(struct snd_seq_timer *tmr)
return -EINVAL;
snd_timer_start(tmr->timeri, tmr->ticks);
tmr->running = 1;
- do_gettimeofday(&tmr->last_update);
+ ktime_get_ts64(&tmr->last_update);
return 0;
}
@@ -420,7 +420,7 @@ static int seq_timer_continue(struct snd_seq_timer *tmr)
}
snd_timer_start(tmr->timeri, tmr->ticks);
tmr->running = 1;
- do_gettimeofday(&tmr->last_update);
+ ktime_get_ts64(&tmr->last_update);
return 0;
}
@@ -444,17 +444,12 @@ snd_seq_real_time_t snd_seq_timer_get_cur_time(struct snd_seq_timer *tmr)
spin_lock_irqsave(&tmr->lock, flags);
cur_time = tmr->cur_time;
if (tmr->running) {
- struct timeval tm;
- int usec;
- do_gettimeofday(&tm);
- usec = (int)(tm.tv_usec - tmr->last_update.tv_usec);
- if (usec < 0) {
- cur_time.tv_nsec += (1000000 + usec) * 1000;
- cur_time.tv_sec += tm.tv_sec - tmr->last_update.tv_sec - 1;
- } else {
- cur_time.tv_nsec += usec * 1000;
- cur_time.tv_sec += tm.tv_sec - tmr->last_update.tv_sec;
- }
+ struct timespec64 tm;
+
+ ktime_get_ts64(&tm);
+ tm = timespec64_sub(tm, tmr->last_update);
+ cur_time.tv_nsec = tm.tv_nsec;
+ cur_time.tv_sec = tm.tv_sec;
snd_seq_sanity_real_time(&cur_time);
}
spin_unlock_irqrestore(&tmr->lock, flags);
diff --git a/sound/core/seq/seq_timer.h b/sound/core/seq/seq_timer.h
index 88dfb71805ae..9506b661fe5b 100644
--- a/sound/core/seq/seq_timer.h
+++ b/sound/core/seq/seq_timer.h
@@ -52,7 +52,7 @@ struct snd_seq_timer {
unsigned int skew;
unsigned int skew_base;
- struct timeval last_update; /* time of last clock update, used for interpolation */
+ struct timespec64 last_update; /* time of last clock update, used for interpolation */
spinlock_t lock;
};
--
2.9.0