From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f180.google.com (mail-dy1-f180.google.com [74.125.82.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8EA63EEA8 for ; Wed, 17 Jun 2026 01:30:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781659845; cv=none; b=LgYa/yQq7wmDn+WI8kjTxsv4+E80UqL4M1mQmClejaVhWQMdLYO/MtNW9SBXA7W5H3Yw8M6ZZCENYViI2ClTyPOkoPlTFvrqc+7lIs82cmw1L0i6H3W+DFF0uyYb55yD3c5ma/IAZB4B+2Qx9mxC0ZaM99P10UnRIHtbHtG2JOA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781659845; c=relaxed/simple; bh=Fnmd794AbnXpu3k3viU+pwAgaaSfmyIGqDXeEpfFxjI=; h=Mime-Version:Content-Type:Date:Message-Id:Cc:Subject:From:To: References:In-Reply-To; b=F3ABW0gesFN3nnAiuj+oyszEh/NRutipZ2uw2WGC42YftzSXEzsh1MxmU6McO0wJn1MAm8435FHQQtwCQzHJ2ff8VqanZQcNEq8ukhnMTfdGoFIXHIHXuDY24qjsSZBbjogwCLd6HBMRxmH54vx/JLPWlaQf9Aa4nSbwDV+/7gE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=etsalapatis.com; spf=pass smtp.mailfrom=etsalapatis.com; dkim=pass (2048-bit key) header.d=etsalapatis-com.20251104.gappssmtp.com header.i=@etsalapatis-com.20251104.gappssmtp.com header.b=h5R623+v; arc=none smtp.client-ip=74.125.82.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=etsalapatis.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=etsalapatis.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=etsalapatis-com.20251104.gappssmtp.com header.i=@etsalapatis-com.20251104.gappssmtp.com header.b="h5R623+v" Received: by mail-dy1-f180.google.com with SMTP id 5a478bee46e88-307263ad0cbso8314782eec.0 for ; Tue, 16 Jun 2026 18:30:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=etsalapatis-com.20251104.gappssmtp.com; s=20251104; t=1781659842; x=1782264642; darn=vger.kernel.org; h=in-reply-to:references:to:from:subject:cc:message-id:date :content-transfer-encoding:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=foa9TfDTwAbcXqfmpgXrr65v3TLgk179Ri/oJcEA6IE=; b=h5R623+vyrd0HpXH+0XiaqttUSwHKtTR39ZM8Vs4hYrugaahvd4/SNl1+42UaszDqt 8jJcw7djVHWcghN4EkCA8a8bRbQpz9eQMbFW8sEaqo7thZahXwq2B40gB9CffJrMHEIA lw9ssEBjv8YDYknvlIrR1dcz5FZ782cjE10J+Wcw99o083ckOrv1V2AZJdAtumhQEORw jnenK6LguPTNcaZt11sr+X2rxu8V3kFBbHnORzNZweFCV/3aCMop2/NghmmUMDeSKDr8 YQN0Ie79r2WJct/4dvjaAGrIsr20v8IByw/BsTdbKYJ3My0y0HMS7Xnqk3dUoob41epI PqBQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781659842; x=1782264642; h=in-reply-to:references:to:from:subject:cc:message-id:date :content-transfer-encoding:mime-version:x-gm-gg:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=foa9TfDTwAbcXqfmpgXrr65v3TLgk179Ri/oJcEA6IE=; b=k5iuSD4lXw84DEYEpIzJTn7pVOTrjaWWrA2c7C9KAZ3rfexHUH4yi3du5XpEjmFre9 6mvSOlxvt8+O8B5jCWQJcSosvi2n6ljVvvqFGt4UEZGMP8T213K6uzNaI/MA1imH8DzF TIWIDk8pn8x9pF+HSWtJuw45ALap0HNk8MeVm6PaZR5J8+XCpYtA3sUml031pSushwxo p9Zj7yDb2whyIdHU0OP+no2HmPg0aqEF2tjRe07BE5k2Xden+whXZ0fp5J3JZ/iLFKTn 4pg9bT+VLsV3vOlgMG9jYun8nryAQC9auu2mfMd9L0o55ME+9kp1RvxwZRH19du7rEiy U+jg== X-Forwarded-Encrypted: i=1; AFNElJ9UZAOrlUYlpQeRFdLsoJF7XfROcKzxo3c40os0g4P8xKr7Zhw2TdfGX6NLfcorAfd0EbuH9FOrNImKkr1/dik=@vger.kernel.org X-Gm-Message-State: AOJu0YwNVtNd+rnF/EH+g4oB5nFMKA0zjR2+lhMnFY8O7v/5ZFqblzjU fHXsDn/IjYAjDxO9Qg1EJxcc2n67LfvlQlm6EBwvfI/47qDwTyaZzWqSwHbXGmUxczA= X-Gm-Gg: AfdE7ckRYEFX8aIH7KlwL+JBfUCo6t9LcTZdzTYVfi1fKiDRqwaQ1M+g+tpv68mNYAV u1AU9mBS9kJrMb3eByhqJKjKdQRv84iPZ9ZUsbzPBVbqE7tQWDRzkDtsHymTqRGWG8JBeh+ocCI SID0lmpBu59KaleiUEk/Jm7qxWrTOmvTp+l3RVi4IXXJBKHAq/renJX/l8FZcLxzEbr02EP/pNv 45i7a/fAowBdYkKn53gPmiZYsVTzg4QHljR9UDV0q2P2fwF6+/xlBzjOu0KR7JnM4jx/QtzaInA 57h39NopbcOhlK1kmXIVEppMJ71UgoVyfAwEQ1OzRcevl+x+TEH/EI2kYNSqjSeozGa+Yl/CPHY eQImgMWwKqKcpjMeUR3bva6YajbiT3DNmlr/B0i6DleH9SEr7Klx0MoPihp05irP07ZLjUN9kuU TuFDUr X-Received: by 2002:a05:7301:100b:b0:307:934e:da79 with SMTP id 5a478bee46e88-30bca0aacbbmr1227152eec.34.1781659841751; Tue, 16 Jun 2026 18:30:41 -0700 (PDT) Received: from localhost ([2620:10d:c090:600::2568]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3081ddaf69asm21886860eec.0.2026.06.16.18.30.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 16 Jun 2026 18:30:41 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 16 Jun 2026 21:30:38 -0400 Message-Id: Cc: , , , "Andrew Werner" , "Zvi Effron" , "Andrii Nakryiko" Subject: Re: [PATCH bpf 4/6] libbpf: ringbuf: Use compiler atomics From: "Emil Tsalapatis" To: "Tamir Duberstein" , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Martin KaFai Lau" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , "Shuah Khan" , "Andrea Righi" , "Xu Kuohai" , "Andrea Righi" X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20260613-bpf-ringbuf-fixes-v1-0-e623481cb724@kernel.org> <20260613-bpf-ringbuf-fixes-v1-4-e623481cb724@kernel.org> In-Reply-To: <20260613-bpf-ringbuf-fixes-v1-4-e623481cb724@kernel.org> On Sat Jun 13, 2026 at 9:48 PM EDT, Tamir Duberstein wrote: > Consumer-side ring buffer code uses architecture-specific smp_* helpers > for shared memory accesses. > > Use compiler atomics instead. They provide equivalent acquire and > release ordering through a portable userspace interface and allow the > next commit to use compiler fences in the wakeup protocol without mixing > atomic interfaces. > > Assisted-by: Codex:gpt-5.5 > Signed-off-by: Tamir Duberstein Reviewed-by: Emil Tsalapatis > --- > tools/lib/bpf/ringbuf.c | 20 +++++++++++--------- > 1 file changed, 11 insertions(+), 9 deletions(-) > > diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c > index b7adce37b519..1c24a83f59d5 100644 > --- a/tools/lib/bpf/ringbuf.c > +++ b/tools/lib/bpf/ringbuf.c > @@ -264,13 +264,13 @@ static int64_t ringbuf_process_ring(struct ring *r,= size_t n) > if (n =3D=3D 0) > return 0; > =20 > - cons_pos =3D smp_load_acquire(r->consumer_pos); > + cons_pos =3D __atomic_load_n(r->consumer_pos, __ATOMIC_ACQUIRE); > do { > got_new_data =3D false; > - prod_pos =3D smp_load_acquire(r->producer_pos); > + prod_pos =3D __atomic_load_n(r->producer_pos, __ATOMIC_ACQUIRE); > while (cons_pos !=3D prod_pos) { > len_ptr =3D r->data + (cons_pos & r->mask); > - len =3D smp_load_acquire(len_ptr); > + len =3D __atomic_load_n(len_ptr, __ATOMIC_ACQUIRE); > =20 > /* sample not committed yet, bail out for now */ > if (len & BPF_RINGBUF_BUSY_BIT) > @@ -284,14 +284,16 @@ static int64_t ringbuf_process_ring(struct ring *r,= size_t n) > err =3D r->sample_cb(r->ctx, sample, len); > if (err < 0) { > /* update consumer pos and bail out */ > - smp_store_release(r->consumer_pos, > - cons_pos); > + __atomic_store_n(r->consumer_pos, > + cons_pos, > + __ATOMIC_RELEASE); > return err; > } > cnt++; > } > =20 > - smp_store_release(r->consumer_pos, cons_pos); > + __atomic_store_n(r->consumer_pos, cons_pos, > + __ATOMIC_RELEASE); > =20 > if (cnt >=3D n) > goto done; > @@ -406,8 +408,8 @@ struct ring *ring_buffer__ring(struct ring_buffer *rb= , unsigned int idx) > =20 > unsigned long ring__consumer_pos(const struct ring *r) > { > - /* Synchronizes with smp_store_release() in ringbuf_process_ring(). */ > - return smp_load_acquire(r->consumer_pos); > + /* Synchronizes with the release store in ringbuf_process_ring(). */ > + return __atomic_load_n(r->consumer_pos, __ATOMIC_ACQUIRE); > } > =20 > unsigned long ring__producer_pos(const struct ring *r) > @@ -415,7 +417,7 @@ unsigned long ring__producer_pos(const struct ring *r= ) > /* Synchronizes with smp_store_release() in __bpf_ringbuf_reserve() in > * the kernel. > */ > - return smp_load_acquire(r->producer_pos); > + return __atomic_load_n(r->producer_pos, __ATOMIC_ACQUIRE); > } > =20 > size_t ring__avail_data_size(const struct ring *r)