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Sun, 01 Feb 2026 19:12:25 -0800 (PST) Received: from localhost.localdomain ([116.128.244.171]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a88b6e4110sm124318605ad.84.2026.02.01.19.12.18 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sun, 01 Feb 2026 19:12:25 -0800 (PST) From: chengkaitao To: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, yangfeng@kylinos.cn, alexei.starovoitov@gmail.com Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, Chengkaitao Subject: [PATCH v3 0/3] bpf/verifier: Expand the usage scenarios of bpf_kptr_xchg Date: Mon, 2 Feb 2026 11:12:12 +0800 Message-ID: <20260202031214.69958-1-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chengkaitao When using bpf_kptr_xchg, we triggered the following error: 31: (85) call bpf_kptr_xchg#194 function calls are not allowed while holding a lock bpf_kptr_xchg can now be used in lock-held contexts, so we extended its usage scope in [patch 1/2]. When writing test cases using bpf_kptr_xchg and bpf_rbtree_*, the following approach must be followed: bpf_spin_lock(&lock); rb_n = bpf_rbtree_root(&root); while (rb_n && can_loop) { rb_n = bpf_rbtree_remove(&root, rb_n); if (!rb_n) goto fail; tnode = container_of(rb_n, struct tree_node, node); node_data = bpf_kptr_xchg(&tnode->node_data, NULL); if (!node_data) goto fail; data = node_data->data; /* use data to do something */ node_data = bpf_kptr_xchg(&tnode->node_data, node_data); if (node_data) goto fail; bpf_rbtree_add(&root, rb_n, less); if (lookup_key < tnode->key) rb_n = bpf_rbtree_left(&root, rb_n); else rb_n = bpf_rbtree_right(&root, rb_n); } bpf_spin_unlock(&lock); The above illustrates a lock-remove-read-add-unlock workflow, which exhibits lower performance. To address this, we introduced support for a streamlined lock-read-unlock operation in [patch 2/2]. Changes in v3: - Fix compilation errors Changes in v2: - Allow using bpf_kptr_xchg even if the NON_OWN_REF flag is set - Add test case Link to V2: https://lore.kernel.org/all/20260201031607.32940-1-pilgrimtao@gmail.com/ Link to V1: https://lore.kernel.org/all/20260122081426.78472-1-pilgrimtao@gmail.com/ Chengkaitao (3): bpf/verifier: allow calling bpf_kptr_xchg while holding a lock bpf/verifier: allow using bpf_kptr_xchg even if the NON_OWN_REF flag is set selftests/bpf: Add supplementary tests for bpf_kptr_xchg kernel/bpf/verifier.c | 7 +- .../testing/selftests/bpf/prog_tests/rbtree.c | 6 + tools/testing/selftests/bpf/progs/bpf_misc.h | 4 + .../selftests/bpf/progs/rbtree_search_kptr.c | 164 ++++++++++++++++++ 4 files changed, 179 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/rbtree_search_kptr.c -- 2.50.1 (Apple Git-155)