From patchwork Thu Sep 1 06:19:38 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hou Tao X-Patchwork-Id: 12961867 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ACCDFC65C0D for ; Thu, 1 Sep 2022 06:01:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230148AbiIAGBo (ORCPT ); Thu, 1 Sep 2022 02:01:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38774 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233269AbiIAGBk (ORCPT ); Thu, 1 Sep 2022 02:01:40 -0400 Received: from dggsgout11.his.huawei.com (unknown [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A4A3CE3C06 for ; Wed, 31 Aug 2022 23:01:36 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.143]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4MJ9PN1lYCzlDyP for ; Thu, 1 Sep 2022 14:00:08 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.124.27]) by APP2 (Coremail) with SMTP id Syh0CgDHGXO5ShBjaMHaAA--.4132S8; Thu, 01 Sep 2022 14:01:34 +0800 (CST) From: Hou Tao To: bpf@vger.kernel.org Cc: Song Liu , Sebastian Andrzej Siewior , Hao Sun , Hao Luo , Andrii Nakryiko , Yonghong Song , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , KP Singh , "David S . Miller" , Jakub Kicinski , Stanislav Fomichev , Jiri Olsa , John Fastabend , Lorenz Bauer , houtao1@huawei.com Subject: [PATCH bpf-next v2 4/4] selftests/bpf: Test concurrent updates on bpf_task_storage_busy Date: Thu, 1 Sep 2022 14:19:38 +0800 Message-Id: <20220901061938.3789460-5-houtao@huaweicloud.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20220901061938.3789460-1-houtao@huaweicloud.com> References: <20220901061938.3789460-1-houtao@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: Syh0CgDHGXO5ShBjaMHaAA--.4132S8 X-Coremail-Antispam: 1UD129KBjvJXoW3Ary8tF4UGw4rJry3WrWktFb_yoW7tw1xpa yIkF90krs5J3Z5Jr1rXwsrAry5K3Z3Za17Crs5GF93Aw40qF95Xr1xKr17ZFyfWw4YqFW3 ZrsIqF45Gr1DJaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUBIb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6r1S6rWUM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUAV Cq3wA2048vs2IY020Ec7CjxVAFwI0_Xr0E3s1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0 rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267 AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E 14v26rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7 xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Y z7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1l42xK82IYc2 Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s02 6x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r4a6rW5MIIYrxkI7VAKI48JMIIF0x vE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26F4j6r4UJwCI42IY 6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aV CY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7IU13l1DUUUUU== X-CM-SenderInfo: xkrx3t3r6k3tpzhluzxrxghudrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Hou Tao Under full preemptible kernel, task local storage lookup operations on the same CPU may update per-cpu bpf_task_storage_busy concurrently. If the update of bpf_task_storage_busy is not preemption safe, the final value of bpf_task_storage_busy may become not-zero forever and bpf_task_storage_trylock() will always fail. So add a test case to ensure the update of bpf_task_storage_busy is preemption safe. Will skip the test case when CONFIG_PREEMPT is disabled, and it can only reproduce the problem probabilistically. By increasing TASK_STORAGE_MAP_NR_LOOP and running it under ARM64 VM with 4-cpus, it takes about four rounds to reproduce: > test_maps is modified to only run test_task_storage_map_stress_lookup() $ export TASK_STORAGE_MAP_NR_THREAD=256 $ export TASK_STORAGE_MAP_NR_LOOP=81920 $ export TASK_STORAGE_MAP_PIN_CPU=1 $ time ./test_maps test_task_storage_map_stress_lookup(135):FAIL:bad bpf_task_storage_busy got -2 real 0m24.743s user 0m6.772s sys 0m17.966s Signed-off-by: Hou Tao --- .../bpf/map_tests/task_storage_map.c | 122 ++++++++++++++++++ .../bpf/progs/read_bpf_task_storage_busy.c | 39 ++++++ 2 files changed, 161 insertions(+) create mode 100644 tools/testing/selftests/bpf/map_tests/task_storage_map.c create mode 100644 tools/testing/selftests/bpf/progs/read_bpf_task_storage_busy.c diff --git a/tools/testing/selftests/bpf/map_tests/task_storage_map.c b/tools/testing/selftests/bpf/map_tests/task_storage_map.c new file mode 100644 index 000000000000..1adc9c292eb2 --- /dev/null +++ b/tools/testing/selftests/bpf/map_tests/task_storage_map.c @@ -0,0 +1,122 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 2022. Huawei Technologies Co., Ltd */ +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#include "test_maps.h" +#include "task_local_storage_helpers.h" +#include "read_bpf_task_storage_busy.skel.h" + +struct lookup_ctx { + bool start; + bool stop; + int pid_fd; + int map_fd; + int loop; +}; + +static void *lookup_fn(void *arg) +{ + struct lookup_ctx *ctx = arg; + long value; + int i = 0; + + while (!ctx->start) + usleep(1); + + while (!ctx->stop && i++ < ctx->loop) + bpf_map_lookup_elem(ctx->map_fd, &ctx->pid_fd, &value); + return NULL; +} + +static void abort_lookup(struct lookup_ctx *ctx, pthread_t *tids, unsigned int nr) +{ + unsigned int i; + + ctx->stop = true; + ctx->start = true; + for (i = 0; i < nr; i++) + pthread_join(tids[i], NULL); +} + +void test_task_storage_map_stress_lookup(void) +{ +#define MAX_NR_THREAD 4096 + unsigned int i, nr = 256, loop = 8192, cpu = 0; + struct read_bpf_task_storage_busy *skel; + pthread_t tids[MAX_NR_THREAD]; + struct lookup_ctx ctx; + cpu_set_t old, new; + const char *cfg; + int err; + + cfg = getenv("TASK_STORAGE_MAP_NR_THREAD"); + if (cfg) { + nr = atoi(cfg); + if (nr > MAX_NR_THREAD) + nr = MAX_NR_THREAD; + } + cfg = getenv("TASK_STORAGE_MAP_NR_LOOP"); + if (cfg) + loop = atoi(cfg); + cfg = getenv("TASK_STORAGE_MAP_PIN_CPU"); + if (cfg) + cpu = atoi(cfg); + + skel = read_bpf_task_storage_busy__open_and_load(); + err = libbpf_get_error(skel); + CHECK(err, "open_and_load", "error %d\n", err); + + /* Only for a fully preemptible kernel */ + if (!skel->kconfig->CONFIG_PREEMPT) + return; + + /* Save the old affinity setting */ + sched_getaffinity(getpid(), sizeof(old), &old); + + /* Pinned on a specific CPU */ + CPU_ZERO(&new); + CPU_SET(cpu, &new); + sched_setaffinity(getpid(), sizeof(new), &new); + + ctx.start = false; + ctx.stop = false; + ctx.pid_fd = sys_pidfd_open(getpid(), 0); + ctx.map_fd = bpf_map__fd(skel->maps.task); + ctx.loop = loop; + for (i = 0; i < nr; i++) { + err = pthread_create(&tids[i], NULL, lookup_fn, &ctx); + if (err) { + abort_lookup(&ctx, tids, i); + CHECK(err, "pthread_create", "error %d\n", err); + goto out; + } + } + + ctx.start = true; + for (i = 0; i < nr; i++) + pthread_join(tids[i], NULL); + + skel->bss->pid = getpid(); + err = read_bpf_task_storage_busy__attach(skel); + CHECK(err, "attach", "error %d\n", err); + + /* Trigger program */ + syscall(SYS_gettid); + skel->bss->pid = 0; + + CHECK(skel->bss->busy != 0, "bad bpf_task_storage_busy", "got %d\n", skel->bss->busy); +out: + read_bpf_task_storage_busy__destroy(skel); + /* Restore affinity setting */ + sched_setaffinity(getpid(), sizeof(old), &old); +} diff --git a/tools/testing/selftests/bpf/progs/read_bpf_task_storage_busy.c b/tools/testing/selftests/bpf/progs/read_bpf_task_storage_busy.c new file mode 100644 index 000000000000..a47bb0120719 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/read_bpf_task_storage_busy.c @@ -0,0 +1,39 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 2022. Huawei Technologies Co., Ltd */ +#include "vmlinux.h" +#include +#include + +extern bool CONFIG_PREEMPT __kconfig __weak; +extern const int bpf_task_storage_busy __ksym; + +char _license[] SEC("license") = "GPL"; + +int pid = 0; +int busy = 0; + +struct { + __uint(type, BPF_MAP_TYPE_TASK_STORAGE); + __uint(map_flags, BPF_F_NO_PREALLOC); + __type(key, int); + __type(value, long); +} task SEC(".maps"); + +SEC("raw_tp/sys_enter") +int BPF_PROG(read_bpf_task_storage_busy) +{ + int *value; + int key; + + if (!CONFIG_PREEMPT) + return 0; + + if (bpf_get_current_pid_tgid() >> 32 != pid) + return 0; + + value = bpf_this_cpu_ptr(&bpf_task_storage_busy); + if (value) + busy = *value; + + return 0; +}