linux-kernel - Re: [PATCH] psi-pressure-stall-information-for-cpu-memory-and-io-fix-fix-fix

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Message-ID: <20180717151758.GI2494@hirez.programming.kicks-ass.net>
Date:   Tue, 17 Jul 2018 17:17:58 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     akpm@...ux-foundation.org, Ingo Molnar <mingo@...hat.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH]
  psi-pressure-stall-information-for-cpu-memory-and-io-fix-fix-fix

On Tue, Jul 17, 2018 at 03:51:24PM +0200, Arnd Bergmann wrote:
> The addition of do_div() did not do the right thing, as it assigned the
> result of the multiplication to an 'unsigned long', which truncates
> it before the division. GCC warns in various ways about this depending
> on the architecuture, e.g.
> 
> arch/arm/include/asm/div64.h:33:45: note: expected 'uint64_t *' {aka 'long long unsigned int *'} but argument is of type 'long unsigned int *'
> 
> This uses div_u64() instead. This is probably still a bad idea since
> we should avoid 64-bit division altogether in the scheduler, but at
> least it does the correct calculation.
> 
> Fixes: 13a67bcb35f5 ("psi-pressure-stall-information-for-cpu-memory-and-io-fix-fix")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> Please fold into the fix

Please drop the entire PSI series instead.