From: Peter Zijlstra <peterz@infradead.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
Shaokun Zhang <zhangshaokun@hisilicon.com>,
David Miller <davem@davemloft.net>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
jinyuqi@huawei.com, kuznet@ms2.inr.ac.ru,
yoshfuji@linux-ipv6.org, edumazet@google.com,
guoyang2@huawei.com, Will Deacon <will@kernel.org>
Subject: Re: [PATCH] net: optimize cmpxchg in ip_idents_reserve
Date: Mon, 20 Jan 2020 09:18:58 +0100 [thread overview]
Message-ID: <20200120081858.GI14879@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <45224c36-9941-aae5-aca4-e2c8e3723355@gmail.com>
On Fri, Jan 17, 2020 at 10:48:19AM -0800, Eric Dumazet wrote:
>
>
> On 1/17/20 10:38 AM, Arvind Sankar wrote:
> > On Fri, Jan 17, 2020 at 10:16:45AM -0800, Eric Dumazet wrote:
> >> Wasńt it the case back in 2016 already for linux-4.8 ?
> >>
> >> What will prevent someone to send another report to netdev/lkml ?
> >>
> >> -fno-strict-overflow support is not a prereq for CONFIG_UBSAN.
> >>
> >> Fact that we kept in lib/ubsan.c and lib/test_ubsan.c code for
> >> test_ubsan_add_overflow() and test_ubsan_sub_overflow() is disturbing.
> >>
> >
> > No, it was bumped in 2018 in commit cafa0010cd51 ("Raise the minimum
> > required gcc version to 4.6"). That raised it from 3.2 -> 4.6.
> >
>
> This seems good to me, for gcc at least.
>
> Maybe it is time to enfore -fno-strict-overflow in KBUILD_CFLAGS
> instead of making it conditional.
IIRC there was a bug in UBSAN vs -fwrapv/-fno-strict-overflow that was
only fixed in gcc-8 or 9 or so.
So while the -fwrapv/-fno-strict-overflow flag has been correctly
supported since like forever, UBSAN was buggy until quite recent when
used in conjustion with that flag.
next prev parent reply other threads:[~2020-01-20 8:19 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 3:23 [PATCH] net: optimize cmpxchg in ip_idents_reserve Shaokun Zhang
2020-01-16 12:27 ` David Miller
2020-01-16 14:05 ` Shaokun Zhang
2020-01-16 15:12 ` Eric Dumazet
2020-01-16 15:19 ` Eric Dumazet
2020-01-17 6:54 ` Shaokun Zhang
2020-01-17 12:32 ` Peter Zijlstra
2020-01-17 16:35 ` Eric Dumazet
2020-01-17 18:03 ` Arvind Sankar
2020-01-17 18:16 ` Eric Dumazet
2020-01-17 18:38 ` Arvind Sankar
2020-01-17 18:48 ` Eric Dumazet
2020-01-20 8:18 ` Peter Zijlstra [this message]
2020-05-07 9:12 ` Shaokun Zhang
2020-05-07 13:49 ` Eric Dumazet
2020-01-19 3:46 ` Shaokun Zhang
2020-01-19 4:12 ` Eric Dumazet
2020-01-21 2:40 ` Shaokun Zhang
2020-01-22 8:49 ` Peter Zijlstra
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