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 3197617A305; Fri, 19 Jun 2026 00:27:26 +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=1781828847; cv=none; b=VN8y2V3Fi5Ngiw3Sg2SKAeq4+4mjl6cNfXFtv33xNcA+HF+/i8zjrS5kSemWf9/ciJlxy2ZSwqsYKi+fuANKx0rCw2ssxGQZpFq7t1Bu70KUSh+hYam1mUbkX7MuRSAE5mjPEsaqLiSXRVi2yJksNG7fx45yBckCY238QSl+QIM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781828847; c=relaxed/simple; bh=N5XifisHN3nS4YI7Gx7dcpOUkKbPumxrjtJXP2wrHOg=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=dEOQE0OhIK0aloo6rEGLm3Skod/PphYx/VJOIcC3RWzjhB0HEjLGJxKvrgHqqY0mmufWJYGL/7wtkJlLOIyaiLN/aB6G5tbkHo+y2vgVcYIF3r+Vua0Ycy9HnqA+W70gdDrF8Oxn+sXSeXDYh6YeCsdV34ba9BTK4wQg/rw3hXQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iRCVgr3l; 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="iRCVgr3l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96DA41F00A3A; Fri, 19 Jun 2026 00:27:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781828846; bh=CL2kfO0YaZ3LrY3n9ruy4IxSrOCHi1fzSmxILQP3SrA=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=iRCVgr3lMRuuvoUo721gmryrkp6A6GSkYd5GF2XwJQjYJ53XYw+LvoEnEqVyooXb/ 4Gu9Zjt2sCEov52vuHtp/HqOnL7tJDNkl9D7/cJoKn3fwWKBsnT6jUw/bdSPWHb9sA IgmofFkGeatJmOkOwmI0v1pZhJVBEnqGKE1AwWtD29VV78AJRkHAb71aTdI88oKUJh v8yCAAJOgYgScc3rWRoMiRX5c63FXI/PL4Fd9c8DhLikiOjO6mBtp5hAavokwqwCS0 DBUBBjwW+MDVRuahChf/z7RuftbcD0cjHhet3rc6CQco/155EbyoxIhfmop9pGjUGc Iv5H+XoDKNymA== From: Tamir Duberstein Date: Thu, 18 Jun 2026 20:26:45 -0400 Subject: [PATCH bpf v2 7/8] libbpf: ringbuf: Use compiler atomics Precedence: bulk X-Mailing-List: linux-kselftest@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: <20260618-bpf-ringbuf-fixes-v2-7-33fde039ddf3@kernel.org> References: <20260618-bpf-ringbuf-fixes-v2-0-33fde039ddf3@kernel.org> In-Reply-To: <20260618-bpf-ringbuf-fixes-v2-0-33fde039ddf3@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 , Bing-Jhong Billy Jheng , David Vernet Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Werner , Zvi Effron , Andrii Nakryiko , Emil Tsalapatis , Tamir Duberstein X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2897; i=tamird@kernel.org; h=from:subject:message-id; bh=N5XifisHN3nS4YI7Gx7dcpOUkKbPumxrjtJXP2wrHOg=; b=owGbwMvMwCV2wYdPVfy60HTG02pJDFkmPTc+cp69K37v/pSbL+y1WHnnze1MbO7Q+95QpfFXW JRz/Z8tHRNZGMS4GCzFFFkSRQ/tTU+9vUc2891xmDmsTCBDpEUaGICAhYEvNzGv1EjHSM9U21DP 0EjHQMeYgYtTAKZaK4KRYZYQ21PfD8kPgzvYZ1mmF6yd/OBC0a2/Trm8p/pvnbs+3Yjhn0ZTYv7 +0q9zE4p39+66snTD5kBF3mm7AnzuGgWHv1bs5QIA 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. Reviewed-by: Emil Tsalapatis 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 1c5bce2b5e12..141f2cbe56eb 100644 --- a/tools/lib/bpf/ringbuf.c +++ b/tools/lib/bpf/ringbuf.c @@ -270,14 +270,14 @@ 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); /* Positions wrap; the consumer cannot logically pass the producer. */ 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) @@ -291,14 +291,16 @@ 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; @@ -413,8 +415,8 @@ 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) @@ -422,7 +424,7 @@ 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.rc0.159.gbe5d7338c2