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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     Frederic Weisbecker <frederic@kernel.org>,
        Anna-Maria Behnsen <anna-maria@linutronix.de>
Cc:     linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>
Subject: Re: [PATCH] timer: Preserve higher bits of expiration on index calculation
In-Reply-To: <20200715221610.GC16227@lenoir>
References: <20200714072924.6810-1-anna-maria@linutronix.de> <20200715221610.GC16227@lenoir>
Date:   Thu, 16 Jul 2020 16:24:19 +0200
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Frederic Weisbecker <frederic@kernel.org> writes:
> Subject: [PATCH] timer: Preserve higher bits of expiration on index
>  calculation
>
> The higher bits of the timer expiration are cropped while calling
> calc_index() due to the implicit cast from unsigned long to unsigned int.
>
> This loss shouldn't have consequences on the current code since all the
> computation to calculate the index is done on the lower 32 bits.
>
> However we are preparing to return the actual bucket expiration from
> calc_index() in order to properly fix base->next_expiry updates.
> Preserving the higher bits is a requirement to achieve that.

Nice catch!