From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] arm64: bpf: add BPF XADD instruction
Date: Wed, 11 Nov 2015 17:44:01 +0000 [thread overview]
Message-ID: <20151111174401.GO9562@arm.com> (raw)
In-Reply-To: <20151111.123548.1039494689070388545.davem@davemloft.net>
On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote:
> From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> Date: Wed, 11 Nov 2015 09:27:00 -0800
>
> > BPF_XADD == atomic_add() in kernel. period.
> > we are not going to deprecate it or introduce something else.
>
> Agreed, it makes no sense to try and tie C99 or whatever atomic
> semantics to something that is already clearly defined to have
> exactly kernel atomic_add() semantics.
... and which is emitted by LLVM when asked to compile __sync_fetch_and_add,
which has clearly defined (yet conflicting) semantics.
If the discrepancy is in LLVM (and it sounds like it is), then I'll raise
a bug over there instead.
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon@arm.com>
To: David Miller <davem@davemloft.net>
Cc: alexei.starovoitov@gmail.com, daniel@iogearbox.net,
peterz@infradead.org, arnd@arndb.de, yang.shi@linaro.org,
linaro-kernel@lists.linaro.org, eric.dumazet@gmail.com,
zlim.lnx@gmail.com, ast@kernel.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, xi.wang@gmail.com,
catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org,
yhs@plumgrid.com, bblanco@plumgrid.com
Subject: Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction
Date: Wed, 11 Nov 2015 17:44:01 +0000 [thread overview]
Message-ID: <20151111174401.GO9562@arm.com> (raw)
In-Reply-To: <20151111.123548.1039494689070388545.davem@davemloft.net>
On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote:
> From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> Date: Wed, 11 Nov 2015 09:27:00 -0800
>
> > BPF_XADD == atomic_add() in kernel. period.
> > we are not going to deprecate it or introduce something else.
>
> Agreed, it makes no sense to try and tie C99 or whatever atomic
> semantics to something that is already clearly defined to have
> exactly kernel atomic_add() semantics.
... and which is emitted by LLVM when asked to compile __sync_fetch_and_add,
which has clearly defined (yet conflicting) semantics.
If the discrepancy is in LLVM (and it sounds like it is), then I'll raise
a bug over there instead.
Will
next prev parent reply other threads:[~2015-11-11 17:44 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-10 22:41 [PATCH 0/2] arm64: bpf: add BPF_ST and BPF_XADD instructions support Yang Shi
2015-11-10 22:41 ` Yang Shi
2015-11-10 22:41 ` Yang Shi
2015-11-10 22:41 ` [PATCH 1/2] arm64: bpf: add 'store immediate' instruction Yang Shi
2015-11-10 22:41 ` Yang Shi
2015-11-11 2:45 ` Z Lim
2015-11-11 2:45 ` Z Lim
2015-11-11 12:12 ` Will Deacon
2015-11-11 12:12 ` Will Deacon
2015-11-11 12:39 ` Will Deacon
2015-11-11 12:39 ` Will Deacon
2015-11-12 19:33 ` Shi, Yang
2015-11-12 19:33 ` Shi, Yang
2015-11-13 3:45 ` Z Lim
2015-11-13 3:45 ` Z Lim
2015-11-23 19:34 ` Shi, Yang
2015-11-23 19:34 ` Shi, Yang
2015-11-10 22:41 ` [PATCH 2/2] arm64: bpf: add BPF XADD instruction Yang Shi
2015-11-10 22:41 ` Yang Shi
2015-11-11 0:08 ` Eric Dumazet
2015-11-11 0:08 ` Eric Dumazet
2015-11-11 0:26 ` Shi, Yang
2015-11-11 0:26 ` Shi, Yang
2015-11-11 0:42 ` Alexei Starovoitov
2015-11-11 0:42 ` Alexei Starovoitov
2015-11-11 2:52 ` Z Lim
2015-11-11 2:52 ` Z Lim
2015-11-11 8:49 ` Arnd Bergmann
2015-11-11 8:49 ` Arnd Bergmann
2015-11-11 10:24 ` Will Deacon
2015-11-11 10:24 ` Will Deacon
2015-11-11 10:42 ` Daniel Borkmann
2015-11-11 10:42 ` Daniel Borkmann
2015-11-11 11:58 ` Will Deacon
2015-11-11 11:58 ` Will Deacon
2015-11-11 12:21 ` Daniel Borkmann
2015-11-11 12:21 ` Daniel Borkmann
2015-11-11 12:38 ` Will Deacon
2015-11-11 12:38 ` Will Deacon
2015-11-11 12:58 ` Peter Zijlstra
2015-11-11 12:58 ` Peter Zijlstra
2015-11-11 15:52 ` Daniel Borkmann
2015-11-11 15:52 ` Daniel Borkmann
2015-11-11 16:23 ` Will Deacon
2015-11-11 16:23 ` Will Deacon
2015-11-11 17:27 ` Alexei Starovoitov
2015-11-11 17:27 ` Alexei Starovoitov
2015-11-11 17:35 ` David Miller
2015-11-11 17:35 ` David Miller
2015-11-11 17:44 ` Will Deacon [this message]
2015-11-11 17:44 ` Will Deacon
2015-11-11 19:01 ` David Miller
2015-11-11 19:01 ` David Miller
2015-11-11 17:57 ` Peter Zijlstra
2015-11-11 17:57 ` Peter Zijlstra
2015-11-11 18:11 ` Alexei Starovoitov
2015-11-11 18:11 ` Alexei Starovoitov
2015-11-11 18:31 ` Peter Zijlstra
2015-11-11 18:31 ` Peter Zijlstra
2015-11-11 18:41 ` Peter Zijlstra
2015-11-11 18:41 ` Peter Zijlstra
2015-11-11 18:44 ` Peter Zijlstra
2015-11-11 18:44 ` Peter Zijlstra
2015-11-11 18:54 ` Peter Zijlstra
2015-11-11 18:54 ` Peter Zijlstra
2015-11-11 19:55 ` Alexei Starovoitov
2015-11-11 19:55 ` Alexei Starovoitov
2015-11-11 22:21 ` Peter Zijlstra
2015-11-11 22:21 ` Peter Zijlstra
2015-11-11 23:40 ` Alexei Starovoitov
2015-11-11 23:40 ` Alexei Starovoitov
2015-11-11 23:40 ` Alexei Starovoitov
2015-11-12 8:57 ` Peter Zijlstra
2015-11-12 8:57 ` Peter Zijlstra
2015-11-11 18:50 ` Daniel Borkmann
2015-11-11 18:50 ` Daniel Borkmann
2015-11-11 19:04 ` David Miller
2015-11-11 19:04 ` David Miller
2015-11-11 19:23 ` Peter Zijlstra
2015-11-11 19:23 ` Peter Zijlstra
2015-11-11 19:41 ` Daniel Borkmann
2015-11-11 19:41 ` Daniel Borkmann
2015-11-11 18:46 ` Will Deacon
2015-11-11 18:46 ` Will Deacon
2015-11-11 19:01 ` David Miller
2015-11-11 19:01 ` David Miller
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