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>

diff --git a/sound/core/seq/seq_timer.c b/sound/core/seq/seq_timer.c
index 2931049..dcc1028 100644 (file)
--- 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 88dfb71..9506b66 100644 (file)
--- 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;
 };