From: Shaokun Zhang <zhangshaokun@hisilicon.com>
To: Peter Zijlstra <peterz@infradead.org>,
Eric Dumazet <eric.dumazet@gmail.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
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: Thu, 7 May 2020 17:12:23 +0800 [thread overview]
Message-ID: <39ddacf9-adbe-c3f5-45a8-9c5280ef11bb@hisilicon.com> (raw)
In-Reply-To: <20200120081858.GI14879@hirez.programming.kicks-ass.net>
Hi Peter/Eric,
Shall we use atomic_add_return() unconditionally and add some comments? Or I missed
something.
Thanks,
Shaokun
On 2020/1/20 16:18, Peter Zijlstra wrote:
> 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:[~2020-05-07 9:12 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
2020-05-07 9:12 ` Shaokun Zhang [this message]
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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