linux-kernel - Re: [PATCH] ALSA: seq_timer: use monotonic times internally

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Date:	Fri, 17 Jun 2016 22:57:51 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	"Arnd Bergmann" <arnd@...db.de>
Cc:	"Jaroslav Kysela" <perex@...ex.cz>, <alsa-devel@...a-project.org>,
	<y2038@...ts.linaro.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ALSA: seq_timer: use monotonic times internally

On Fri, 17 Jun 2016 17:10:32 +0200,
Arnd Bergmann wrote:
> 
> 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@...db.de>

Thanks, applied.  It's even a nice cleanup!


Takashi