linux-kernel - Re: [PATCH 1/3] time: Add missing implementation for timespec64_add

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Message-ID: <CABeXuvqKwQ=rpdZvk3kmr43koieMHnUvSeeE-+_1kmpMGZay_w@mail.gmail.com>
Date:	Wed, 4 May 2016 08:54:28 -0700
From:	Deepa Dinamani <deepa.kernel@...il.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Arnd Bergmann <arnd@...db.de>, y2038@...ts.linaro.org,
	Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/3] time: Add missing implementation for timespec64_add_safe()

Wanted to add a note here:

> + * Add two timespec64 values and do a safety check for overflow.
> + * It's assumed that both values are valid (>= 0).
> + * And, each timespec64 is in normalized form.
> + */
> +struct timespec64 timespec64_add_safe(const struct timespec64 lhs,
> +                               const struct timespec64 rhs)
> +{
> +       struct timespec64 res;
> +
> +       set_normalized_timespec64(&res, lhs.tv_sec + rhs.tv_sec,
> +                       lhs.tv_nsec + rhs.tv_nsec);
> +
> +       if (unlikely(res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)) {

This check can be reduced to only the first condition if we assume the
timespecs passed in to be normalized.
The current patch maintains the way timespec_add_safe() does it for consistency.

-Deepa