Commit 3915bf29 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Takashi Iwai
Browse files

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: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent d1691338

sound/core/seq/seq_timer.c

+9 −14
Original line number Diff line number Diff line
@@ -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);

sound/core/seq/seq_timer.h

+1 −1
Original line number Diff line number Diff line
@@ -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;

};

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