From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1FF79C43603 for ; Thu, 5 Dec 2019 04:56:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D92EC2073B for ; Thu, 5 Dec 2019 04:56:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="gfu2s4eC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728883AbfLEE4Y (ORCPT ); Wed, 4 Dec 2019 23:56:24 -0500 Received: from mail-pg1-f202.google.com ([209.85.215.202]:34283 "EHLO mail-pg1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728132AbfLEE4Y (ORCPT ); Wed, 4 Dec 2019 23:56:24 -0500 Received: by mail-pg1-f202.google.com with SMTP id w9so1134634pgl.1 for ; Wed, 04 Dec 2019 20:56:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=UGw+elk+Q46fH6zXXZMT2OXr0euljB48U9bBxyx3aus=; b=gfu2s4eCN7BS3urrPU2aXVhzGbhqdTghf4zTXfanfnPJR6n1TBpXTu/d8HOu0BYh+i f1n9hgU5+hFzaHN4lQOl7PddlzKgGAN7pMxAfLkympEk8rJ4ONzktqOyhEINFvZgVxj9 TR1WoRjnK//p9E0AHtVHnOroNAM6YX8LUWhk1ABeglXOxYYIReRlBOZQoZQFo9VdGuoq dfOM5qNBL4SefKjhCumg1qiePTNLmFjZ8295riHQZ+eNki75cmjatTexBNR/qk9DokOM a6fU9tE5H+xHG/XXvCaJLDaKoRimdGJbX0HDc8cvp8tsq5d2ibWBHYdKxfulCEVp+HKj gSJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=UGw+elk+Q46fH6zXXZMT2OXr0euljB48U9bBxyx3aus=; b=VKuzUESRJrcHGODcwUVVuTFRP6Hmfvop5fiFl+vy1WYXkt8PCqv34Wo/Vj9B9cvwG6 3YWeDz7SHBYbyrYHThkeqQcx/NOA6lnqy/CxcGUaRgsd2ROT2Zb0DX+PcaqB5cR1adGi yn91jQEZ24Z4np8SA788s9cW1/jdIGh9jACMZECFdsvF2j++5nil/Q/PPe6hx6CUXdqQ 4DgK34Z7xYU82EXh5xD7o85b9mVGaETiijHACg1yqm4RqzdF+mFkrChkJdzl4aOUAp1H XzRt7Cxs4dhMPFq0sQ5cmV42k7aIWPqDWqOMr976uvVTQEqI7fFtLEi+zkAppadD40K1 nQCg== X-Gm-Message-State: APjAAAWI3sTwRhSoJVIZ9+lZ2zPO2UI11+ng7HqSPv0Am7T3adiXDb3y VkG6dRwJ3TU4Q2/glJmSFyklqrtIah4crw== X-Google-Smtp-Source: APXvYqwhWoUvaZceiyIVIAuL9tg0344t4RWmxDFsB2B2+mJyk2VZ1JxVbDzkbU6IEHBLlJOUs8nilMZy1JmSZA== X-Received: by 2002:a63:f60:: with SMTP id 32mr2149198pgp.206.1575521782759; Wed, 04 Dec 2019 20:56:22 -0800 (PST) Date: Wed, 4 Dec 2019 20:56:19 -0800 Message-Id: <20191205045619.204946-1-edumazet@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.24.0.393.g34dc348eaf-goog Subject: [PATCH] time: tick-sched: Annotate lockless access to last_jiffies_update From: Eric Dumazet To: Thomas Gleixner Cc: linux-kernel , Eric Dumazet , Eric Dumazet , syzbot Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org syzbot (KCSAN) reported a data-race in tick_do_update_jiffies64() [1] Use READ_ONCE() and WRITE_ONCE() to annotate this expected race. [1] BUG: KCSAN: data-race in tick_do_update_jiffies64 / tick_do_update_jiffies64 write to 0xffffffff8603d008 of 8 bytes by interrupt on cpu 1: tick_do_update_jiffies64+0x100/0x250 kernel/time/tick-sched.c:73 tick_sched_do_timer+0xd4/0xe0 kernel/time/tick-sched.c:138 tick_sched_timer+0x43/0xe0 kernel/time/tick-sched.c:1292 __run_hrtimer kernel/time/hrtimer.c:1514 [inline] __hrtimer_run_queues+0x274/0x5f0 kernel/time/hrtimer.c:1576 hrtimer_interrupt+0x22a/0x480 kernel/time/hrtimer.c:1638 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline] smp_apic_timer_interrupt+0xdc/0x280 arch/x86/kernel/apic/apic.c:1135 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830 arch_local_irq_restore arch/x86/include/asm/paravirt.h:756 [inline] kcsan_setup_watchpoint+0x1d4/0x460 kernel/kcsan/core.c:436 check_access kernel/kcsan/core.c:466 [inline] __tsan_read1 kernel/kcsan/core.c:593 [inline] __tsan_read1+0xc2/0x100 kernel/kcsan/core.c:593 kallsyms_expand_symbol.constprop.0+0x70/0x160 kernel/kallsyms.c:79 kallsyms_lookup_name+0x7f/0x120 kernel/kallsyms.c:170 insert_report_filterlist kernel/kcsan/debugfs.c:155 [inline] debugfs_write+0x14b/0x2d0 kernel/kcsan/debugfs.c:256 full_proxy_write+0xbd/0x100 fs/debugfs/file.c:225 __vfs_write+0x67/0xc0 fs/read_write.c:494 vfs_write fs/read_write.c:558 [inline] vfs_write+0x18a/0x390 fs/read_write.c:542 ksys_write+0xd5/0x1b0 fs/read_write.c:611 __do_sys_write fs/read_write.c:623 [inline] __se_sys_write fs/read_write.c:620 [inline] __x64_sys_write+0x4c/0x60 fs/read_write.c:620 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x44/0xa9 read to 0xffffffff8603d008 of 8 bytes by task 0 on cpu 0: tick_do_update_jiffies64+0x2b/0x250 kernel/time/tick-sched.c:62 tick_nohz_update_jiffies kernel/time/tick-sched.c:505 [inline] tick_nohz_irq_enter kernel/time/tick-sched.c:1257 [inline] tick_irq_enter+0x139/0x1c0 kernel/time/tick-sched.c:1274 irq_enter+0x4f/0x60 kernel/softirq.c:354 entering_irq arch/x86/include/asm/apic.h:517 [inline] entering_ack_irq arch/x86/include/asm/apic.h:523 [inline] smp_apic_timer_interrupt+0x55/0x280 arch/x86/kernel/apic/apic.c:1133 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830 native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:571 default_idle_call+0x1e/0x40 kernel/sched/idle.c:94 cpuidle_idle_call kernel/sched/idle.c:154 [inline] do_idle+0x1af/0x280 kernel/sched/idle.c:263 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:355 rest_init+0xec/0xf6 init/main.c:452 arch_call_rest_init+0x17/0x37 start_kernel+0x838/0x85e init/main.c:786 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490 x86_64_start_kernel+0x72/0x76 arch/x86/kernel/head64.c:471 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.0-rc7+ #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Signed-off-by: Eric Dumazet Reported-by: syzbot --- kernel/time/tick-sched.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 8b192e67aabc9d16d8a7b08c0356641b5462c783..a792d21cac645c63468f605207c0c5fd7b356242 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -58,8 +58,9 @@ static void tick_do_update_jiffies64(ktime_t now) /* * Do a quick check without holding jiffies_lock: + * The READ_ONCE() pairs with two updates done later in this function. */ - delta = ktime_sub(now, last_jiffies_update); + delta = ktime_sub(now, READ_ONCE(last_jiffies_update)); if (delta < tick_period) return; @@ -70,8 +71,9 @@ static void tick_do_update_jiffies64(ktime_t now) if (delta >= tick_period) { delta = ktime_sub(delta, tick_period); - last_jiffies_update = ktime_add(last_jiffies_update, - tick_period); + /* Pairs with the lockless read in this function. */ + WRITE_ONCE(last_jiffies_update, + ktime_add(last_jiffies_update, tick_period)); /* Slow path for long timeouts */ if (unlikely(delta >= tick_period)) { @@ -79,8 +81,10 @@ static void tick_do_update_jiffies64(ktime_t now) ticks = ktime_divns(delta, incr); - last_jiffies_update = ktime_add_ns(last_jiffies_update, - incr * ticks); + /* Pairs with the lockless read in this function. */ + WRITE_ONCE(last_jiffies_update, + ktime_add_ns(last_jiffies_update, + incr * ticks)); } do_timer(++ticks); -- 2.24.0.393.g34dc348eaf-goog