From nobody Sat Feb 7 21:05:35 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 808513644C0; Fri, 9 Jan 2026 16:46:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767977162; cv=none; b=ldb3R0a7fYOx6NDBXLu070ZUErUJbf/BOML/1SkHTYQCC/eRa2d9gVmNXGw3DdJgL/3giryRx+6jB4kUUP1/aWJjWxTsXw4XO2/WsL8QLSLEZKPga6Xk0wGd/JkV2R/cVZmMNA3FYTP4t+C5fxQr9xvgzsLQsQG8grgsBtSRTtg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767977162; c=relaxed/simple; bh=qwqr59+EFyHFWI195WTIHNmr8NmyseP9DCtQwOU8gBI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=JvyIzzMmvEOBhIsHw305mfA291hOaYCYSOVeKQ/iIpqTGxzNatHqPdASM4BLH32IGT33V2+iiJ+x0b/JsptAfMUDqkQA0UrAYrS2M8JJemHMo3lc6WmJMVhTXbo3UVUq53M7hEUV6NdzVHDMUcg0WmwiiQ0q01ltJwzt/my1iY4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sQeWOmvB; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="sQeWOmvB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B019FC4CEF1; Fri, 9 Jan 2026 16:46:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767977162; bh=qwqr59+EFyHFWI195WTIHNmr8NmyseP9DCtQwOU8gBI=; h=From:To:Cc:Subject:Date:From; b=sQeWOmvBFHOikesvsi++uX1JDovaS1li9FFZqR5e+QS5IG0YkvBdAMDXs/DI7LBMx nhTI6QAdjW8ZEO0KyaKCcZEZQPDlvriqtYhWhqd8typg+rIdIf9yIw3UL0WSHizNcr 8HrJ9A29VQZkCr0KA9ce40gUYSffraRV7F8lpFVs9Zyci/EtC9/uZmjZgm/GEYZWKi LBUtq2ymSfl3R9LafZAGvDcVAwQ/jotm8zj5EIWtUMGrGFUf31UkfLNq+bKjbWHvx+ 32dK0ykbPIlmicv5DNnPQsGy5PIpQeQ+y0xVT4sDzA6bAavypvNUOMn7/a8utczaOu GrlctFn7wfjPw== From: Tycho Andersen To: Arnaldo Carvalho de Melo , Namhyung Kim Cc: Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , James Clark , Chun-Tse Shao , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Ravi Bangoria , K Prateek Nayak Subject: [PATCH] perf: fix segfault in `lock contention -b` Date: Fri, 9 Jan 2026 09:44:17 -0700 Message-ID: <20260109164417.396138-1-tycho@kernel.org> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: linux-kernel@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" From: "Tycho Andersen (AMD)" When run on a kernel without BTF info, I get: libbpf: kernel BTF is missing at '/sys/kernel/btf/vmlinux', was CONFIG_= DEBUG_INFO_BTF enabled? libbpf: failed to find valid kernel BTF Program received signal SIGSEGV, Segmentation fault. 0x00005555556915b7 in btf.type_cnt () (gdb) bt #0 0x00005555556915b7 in btf.type_cnt () #1 0x0000555555691fbc in btf_find_by_name_kind () #2 0x00005555556920d0 in btf.find_by_name_kind () #3 0x00005555558a1b7c in init_numa_data (con=3D0x7fffffffd0a0) at util= /bpf_lock_contention.c:125 #4 0x00005555558a264b in lock_contention_prepare (con=3D0x7fffffffd0a0= ) at util/bpf_lock_contention.c:313 #5 0x0000555555620702 in __cmd_contention (argc=3D0, argv=3D0x7fffffff= ea10) at builtin-lock.c:2084 #6 0x0000555555622c8d in cmd_lock (argc=3D0, argv=3D0x7fffffffea10) at= builtin-lock.c:2755 #7 0x0000555555651451 in run_builtin (p=3D0x555556104f00 , argc=3D3, argv=3D0x7fffffffea10) at perf.c:349 #8 0x00005555556516ed in handle_internal_command (argc=3D3, argv=3D0x7= fffffffea10) at perf.c:401 #9 0x000055555565184e in run_argv (argcp=3D0x7fffffffe7fc, argv=3D0x7f= ffffffe7f0) at perf.c:445 #10 0x0000555555651b9f in main (argc=3D3, argv=3D0x7fffffffea10) at per= f.c:553 If we really are running -b without BTF info, the error is fatal, so let's propagate it and exit accordingly. Signed-off-by: Tycho Andersen (AMD) CC: Ravi Bangoria CC: K Prateek Nayak --- tools/perf/util/bpf_lock_contention.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lo= ck_contention.c index 7b5671f13c53..0f207e577037 100644 --- a/tools/perf/util/bpf_lock_contention.c +++ b/tools/perf/util/bpf_lock_contention.c @@ -34,7 +34,7 @@ static bool slab_cache_equal(long key1, long key2, void *= ctx __maybe_unused) return key1 =3D=3D key2; } =20 -static void check_slab_cache_iter(struct lock_contention *con) +static int check_slab_cache_iter(struct lock_contention *con) { s32 ret; =20 @@ -43,19 +43,20 @@ static void check_slab_cache_iter(struct lock_contentio= n *con) con->btf =3D btf__load_vmlinux_btf(); if (con->btf =3D=3D NULL) { pr_debug("BTF loading failed: %s\n", strerror(errno)); - return; + return -errno; } =20 ret =3D btf__find_by_name_kind(con->btf, "bpf_iter__kmem_cache", BTF_KIND= _STRUCT); if (ret < 0) { bpf_program__set_autoload(skel->progs.slab_cache_iter, false); pr_debug("slab cache iterator is not available: %d\n", ret); - return; + return ret; } =20 has_slab_iter =3D true; =20 bpf_map__set_max_entries(skel->maps.slab_caches, con->map_nr_entries); + return 0; } =20 static void run_slab_cache_iter(void) @@ -301,7 +302,8 @@ int lock_contention_prepare(struct lock_contention *con) skel->rodata->use_cgroup_v2 =3D 1; } =20 - check_slab_cache_iter(con); + if (check_slab_cache_iter(con) < 0) + return -1; =20 if (con->filters->nr_slabs && has_slab_iter) { skel->rodata->has_slab =3D 1; base-commit: 5572ad8fddecd4a0db19801262072ff5916b7589 --=20 2.52.0