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ALSA: seq_timer: use monotonic times internally 

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@arndb.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Arnd Bergmann 2016-06-17 17:10:32 +02:00 committed by Takashi Iwai
parent d169133889
commit 3915bf2946
2 changed files with 10 additions and 15 deletions
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23
sound/core/seq/seq_timer.c
View File

@ -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);

2
sound/core/seq/seq_timer.h
View File

@ -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;
};