From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DC7C82C21F1; Sun, 14 Jun 2026 01:49:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781401748; cv=none; b=UhZi0NNkoLZbXZzPHGaedtbuP6qql+q/MH23N3CtsvTQWZH5v5gAvogyy9I36/2tc+IWr5BcTzBlw7ICZdJuFByw+rLTEBCVR3p0yRmCDPY1hdcrb3ohyF0nCtT3LNTmTo2ndy6OZMn7hjirhuRtkXYGebBRA8FRnqptg6t403c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781401748; c=relaxed/simple; bh=8dz6/SaOc+F+Uw4uQoNwuNT0SOhzqBTepT6Zbf/lkRY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=mV3RGIS9iaHGxnvD51NO2HJVonBtbRxDJaZrGUnTI/aOZdyKRr3zwrXjZrinkdx875wcxE14YxBJGBZ2AC68F5LPL3qY985AwpbpT5V0EmQqk+119rB4d6vID84s5PNWmAik6Z6jeg0B2u+Gc7NlmBxiis2oSc0LG8m2o391H/I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PDmFKxwo; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PDmFKxwo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C5751F00AC4; Sun, 14 Jun 2026 01:49:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781401745; bh=pVlAB0niwxQq8SW/aQUHkK5p0Bl8aaDn/Fg5ktLe2nw=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=PDmFKxwozMpmyo8+ujtaLp5jiwOmq/gvSIIN7hDwgBUQSPQOAzdVasmnGt/LEWzFM UrhA0tCnYtt18NFNlDms3qWDiVQecr/qCYE3pCCn68atvMvbYkRAk5Stf6Aya5hteI 7xbVKqmxgkn/xVD17pJ/XvhbEn6I6cmZ3n4W3jwZrkk8OH7NvwlXyK2VaIWzqMFE2t G1Jsxd8+GtGGWtLm1T+tfdnOenYJYt99zmWDQKwlfmZa4t4DOWQc12taz8d6pIH7y/ /FsOEiGMwKXXx66Q6Bvv77RRbmaTyvsqURMxdo507OualQu0O4gkNT4ZxxkxEi0cxI SAJb5mjnERE/Q== From: Tamir Duberstein Date: Sat, 13 Jun 2026 21:48:47 -0400 Subject: [PATCH bpf 4/6] libbpf: ringbuf: Use compiler atomics Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260613-bpf-ringbuf-fixes-v1-4-e623481cb724@kernel.org> References: <20260613-bpf-ringbuf-fixes-v1-0-e623481cb724@kernel.org> In-Reply-To: <20260613-bpf-ringbuf-fixes-v1-0-e623481cb724@kernel.org> To: 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 Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Werner , Zvi Effron , Andrii Nakryiko , Tamir Duberstein X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2768; i=tamird@kernel.org; h=from:subject:message-id; bh=8dz6/SaOc+F+Uw4uQoNwuNT0SOhzqBTepT6Zbf/lkRY=; b=owGbwMvMwCV2wYdPVfy60HTG02pJDFl6HG3Oi27VMdyeyckqPPO4fOrpGU/n//uXcZxRw/Wea oRIlIJ4x0QWBjEuBksxRZZE0UN701Nv75HNfHccZg4rE8gQaZEGBiBgYeDLTcwrNdIx0jPVNtQz NNIx0DFm4OIUgKlefJPhf8IHxVVG4uXhvzzLbqeKnT12WcztSNKOs1J6j+Vv1GctrmT4Hyn2MUH VavMK1pzzHUJCRuKnVAoM7JxaJS1M3e+rav/hBQA= X-Developer-Key: i=tamird@kernel.org; a=openpgp; fpr=5A6714204D41EC844C50273C19D6FF6092365380 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 --- 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 == 0) return 0; - cons_pos = smp_load_acquire(r->consumer_pos); + cons_pos = __atomic_load_n(r->consumer_pos, __ATOMIC_ACQUIRE); do { got_new_data = false; - prod_pos = smp_load_acquire(r->producer_pos); + prod_pos = __atomic_load_n(r->producer_pos, __ATOMIC_ACQUIRE); while (cons_pos != prod_pos) { len_ptr = r->data + (cons_pos & r->mask); - len = smp_load_acquire(len_ptr); + len = __atomic_load_n(len_ptr, __ATOMIC_ACQUIRE); /* 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 = 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++; } - smp_store_release(r->consumer_pos, cons_pos); + __atomic_store_n(r->consumer_pos, cons_pos, + __ATOMIC_RELEASE); if (cnt >= n) goto done; @@ -406,8 +408,8 @@ struct ring *ring_buffer__ring(struct ring_buffer *rb, unsigned int idx) 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); } 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); } size_t ring__avail_data_size(const struct ring *r) -- 2.55.0.rc0.96.gc050c23164