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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 2390AC2D0B1 for ; Tue, 10 Dec 2019 04:02:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED3152080D for ; Tue, 10 Dec 2019 04:02:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575950547; bh=oTekImA/+nyeVowpRPE5W/zaHGtAeTl/S2YCyonCT+Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YgdRqhL72eg4YO8S4dejoQQBHFqTvlf+2PoxwT/TcLQLzZijkA026iL8pb3QL2nhw ZFcO3hzkIwOcDUBihobrD8Tjmz9EjajWPXae+C6xEOe+xoKfEYJJiyT8X2bVI6V1+z DSbNNtTK1NCAiqeQproG9gfeE67MJyoIuMN32wMk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726969AbfLJECA (ORCPT ); Mon, 9 Dec 2019 23:02:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:41458 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726619AbfLJEB7 (ORCPT ); Mon, 9 Dec 2019 23:01:59 -0500 Received: from paulmck-ThinkPad-P72.home (199-192-87-166.static.wiline.com [199.192.87.166]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7E2F820836; Tue, 10 Dec 2019 04:01:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575950518; bh=oTekImA/+nyeVowpRPE5W/zaHGtAeTl/S2YCyonCT+Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kSTbikKxP6JlBINsNOFN8mHsL9YfNH8UXKlI9LK1IaK4ovT385qezvSWmNfxsxIUY uk5AUencqDDPPddoqwO0k+NN0k4V+5rQEpJFwYixqDtkZt/cLj6MMH3rEKGF9lOszu q2RTDZtDuDkC5wFaLMwAtod98+LxFOPRL5ENHSLs= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Marco Elver , "Paul E . McKenney" , Ingo Molnar , Dmitry Vyukov Subject: [PATCH tip/core/rcu 03/10] rcu: Fix data-race due to atomic_t copy-by-value Date: Mon, 9 Dec 2019 20:01:47 -0800 Message-Id: <20191210040154.2498-3-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20191210040122.GA2419@paulmck-ThinkPad-P72> References: <20191210040122.GA2419@paulmck-ThinkPad-P72> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: Marco Elver This fixes a data-race where `atomic_t dynticks` is copied by value. The copy is performed non-atomically, resulting in a data-race if `dynticks` is updated concurrently. This data-race was found with KCSAN: ================================================================== BUG: KCSAN: data-race in dyntick_save_progress_counter / rcu_irq_enter write to 0xffff989dbdbe98e0 of 4 bytes by task 10 on cpu 3: atomic_add_return include/asm-generic/atomic-instrumented.h:78 [inline] rcu_dynticks_snap kernel/rcu/tree.c:310 [inline] dyntick_save_progress_counter+0x43/0x1b0 kernel/rcu/tree.c:984 force_qs_rnp+0x183/0x200 kernel/rcu/tree.c:2286 rcu_gp_fqs kernel/rcu/tree.c:1601 [inline] rcu_gp_fqs_loop+0x71/0x880 kernel/rcu/tree.c:1653 rcu_gp_kthread+0x22c/0x3b0 kernel/rcu/tree.c:1799 kthread+0x1b5/0x200 kernel/kthread.c:255 read to 0xffff989dbdbe98e0 of 4 bytes by task 154 on cpu 7: rcu_nmi_enter_common kernel/rcu/tree.c:828 [inline] rcu_irq_enter+0xda/0x240 kernel/rcu/tree.c:870 irq_enter+0x5/0x50 kernel/softirq.c:347 Reported by Kernel Concurrency Sanitizer on: CPU: 7 PID: 154 Comm: kworker/7:1H Not tainted 5.3.0+ #5 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 Workqueue: kblockd blk_mq_run_work_fn ================================================================== Signed-off-by: Marco Elver Cc: Paul E. McKenney Cc: Josh Triplett Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: Joel Fernandes Cc: Ingo Molnar Cc: Dmitry Vyukov Cc: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- include/trace/events/rcu.h | 4 ++-- kernel/rcu/tree.c | 11 ++++++----- 2 files changed, 8 insertions(+), 7 deletions(-) diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 6612260..697e2c0 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -449,7 +449,7 @@ TRACE_EVENT_RCU(rcu_fqs, */ TRACE_EVENT_RCU(rcu_dyntick, - TP_PROTO(const char *polarity, long oldnesting, long newnesting, atomic_t dynticks), + TP_PROTO(const char *polarity, long oldnesting, long newnesting, int dynticks), TP_ARGS(polarity, oldnesting, newnesting, dynticks), @@ -464,7 +464,7 @@ TRACE_EVENT_RCU(rcu_dyntick, __entry->polarity = polarity; __entry->oldnesting = oldnesting; __entry->newnesting = newnesting; - __entry->dynticks = atomic_read(&dynticks); + __entry->dynticks = dynticks; ), TP_printk("%s %lx %lx %#3x", __entry->polarity, diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 1694a6b..6145e08 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -577,7 +577,7 @@ static void rcu_eqs_enter(bool user) } lockdep_assert_irqs_disabled(); - trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, rdp->dynticks); + trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks)); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); rdp = this_cpu_ptr(&rcu_data); do_nocb_deferred_wakeup(rdp); @@ -650,14 +650,15 @@ static __always_inline void rcu_nmi_exit_common(bool irq) * leave it in non-RCU-idle state. */ if (rdp->dynticks_nmi_nesting != 1) { - trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, rdp->dynticks); + trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, + atomic_read(&rdp->dynticks)); WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */ rdp->dynticks_nmi_nesting - 2); return; } /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ - trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, rdp->dynticks); + trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks)); WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ if (irq) @@ -744,7 +745,7 @@ static void rcu_eqs_exit(bool user) rcu_dynticks_task_exit(); rcu_dynticks_eqs_exit(); rcu_cleanup_after_idle(); - trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, rdp->dynticks); + trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, atomic_read(&rdp->dynticks)); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); WRITE_ONCE(rdp->dynticks_nesting, 1); WARN_ON_ONCE(rdp->dynticks_nmi_nesting); @@ -833,7 +834,7 @@ static __always_inline void rcu_nmi_enter_common(bool irq) } trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="), rdp->dynticks_nmi_nesting, - rdp->dynticks_nmi_nesting + incby, rdp->dynticks); + rdp->dynticks_nmi_nesting + incby, atomic_read(&rdp->dynticks)); WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */ rdp->dynticks_nmi_nesting + incby); barrier(); -- 2.9.5