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Message-ID: <20181105103857.GB22431@hirez.programming.kicks-ass.net>
Date: Mon, 5 Nov 2018 11:38:57 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: Trond Myklebust <trondmy@...merspace.com>,
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Paul McKenney <paulmck@...ux.vnet.ibm.com>, dvyukov@...gle.com
Subject: Re: [RFC PATCH] lib: Introduce generic __cmpxchg_u64() and use it
where needed
On Fri, Nov 02, 2018 at 07:19:15PM +0300, Andrey Ryabinin wrote:
> UBSAN warns about signed overflows despite -fno-strict-overflow if gcc
> version is < 8. I have learned recently that UBSAN in GCC 8 ignores
> signed overflows if -fno-strict-overflow of fwrapv is used.
Ah, good.
> We can always just drop -fsanitize=signed-integer-overflow if it considered too noisy.
I think that is the most consistent beahviour. signed overflow is not UB
in the kernel.
> Although it did catch some real bugs.
If we want an over/under-flow checker, then that should be a separate
plugin and not specific to signed or unsigned.
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