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From: David Vernet <void@manifault.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
	andrii@kernel.org, john.fastabend@gmail.com,
	martin.lau@linux.dev, song@kernel.org, yhs@fb.com,
	kpsingh@kernel.org, sdf@google.com, haoluo@google.com,
	jolsa@kernel.org, tj@kernel.org, joannelkoong@gmail.com,
	linux-kernel@vger.kernel.org, Kernel-team@fb.com
Subject: Re: [PATCH 3/5] bpf: Add bpf_user_ringbuf_drain() helper
Date: Wed, 17 Aug 2022 16:03:28 -0500	[thread overview]
Message-ID: <Yv1XoPoICceMkjH4@maniforge.dhcp.thefacebook.com> (raw)
In-Reply-To: <Yv1OiCYmQhkvRyWS@maniforge.dhcp.thefacebook.com>

On Wed, Aug 17, 2022 at 03:24:40PM -0500, David Vernet wrote:

> [...]
> > right, I think __atomic_store_n() can be used in libbpf for this with
> > seq_cst ordering
> 
> __atomic_store_n(__ATOMIC_SEQ_CST) will do the correct thing on x86, but it
> is not guaranteed to provide a full acq/rel barrier according to the C
> standard. __atomic_store_n(__ATOMIC_SEQ_CST) means "store-release, and also
> participates in the sequentially-consistent global ordering".
> 
> I believe we actually need an __atomic_store_n(__ATOMIC_ACQ_REL) here. I

Sorry, I meant __atomic_exchange_n() rather than __atomic_store_n().

  reply	other threads:[~2022-08-17 21:04 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-08 15:53 [PATCH 1/5] bpf: Clear callee saved regs after updating REG0 David Vernet
2022-08-08 15:53 ` [PATCH 2/5] bpf: Define new BPF_MAP_TYPE_USER_RINGBUF map type David Vernet
2022-08-11 23:22   ` Andrii Nakryiko
2022-08-12 16:21     ` David Vernet
2022-08-11 23:29   ` Andrii Nakryiko
2022-08-12 16:23     ` David Vernet
2022-08-16 18:43       ` Andrii Nakryiko
2022-08-08 15:53 ` [PATCH 3/5] bpf: Add bpf_user_ringbuf_drain() helper David Vernet
2022-08-08 21:55   ` kernel test robot
2022-08-11 23:22   ` Andrii Nakryiko
2022-08-12  0:01     ` David Vernet
2022-08-12  0:46     ` David Vernet
2022-08-16 18:57       ` Andrii Nakryiko
2022-08-16 22:14         ` David Vernet
2022-08-16 22:59           ` Andrii Nakryiko
2022-08-17 20:24             ` David Vernet
2022-08-17 21:03               ` David Vernet [this message]
2022-08-08 15:53 ` [PATCH 4/5] bpf: Add libbpf logic for user-space ring buffer David Vernet
2022-08-11 23:39   ` Andrii Nakryiko
2022-08-12 17:28     ` David Vernet
2022-08-16 19:09       ` Andrii Nakryiko
2022-08-17 14:02         ` David Vernet
2022-08-18  3:05           ` David Vernet
2022-08-08 15:53 ` [PATCH 5/5] selftests/bpf: Add selftests validating the user ringbuf David Vernet
2022-08-08 18:14 ` [PATCH 1/5] bpf: Clear callee saved regs after updating REG0 Joanne Koong
2022-08-08 18:50   ` David Vernet
2022-08-08 23:32     ` Joanne Koong
2022-08-09 12:47       ` David Vernet

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