From patchwork Tue May 11 11:32:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rocco Yue X-Patchwork-Id: 12250763 X-Patchwork-Delegate: kuba@kernel.org 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_GIT 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 D818AC433ED for ; Tue, 11 May 2021 11:46:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E936611AC for ; Tue, 11 May 2021 11:46:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231496AbhEKLrR (ORCPT ); Tue, 11 May 2021 07:47:17 -0400 Received: from mailgw01.mediatek.com ([210.61.82.183]:35917 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S230478AbhEKLrP (ORCPT ); Tue, 11 May 2021 07:47:15 -0400 X-UUID: 2e0ed729685147178540493ee8094e32-20210511 X-UUID: 2e0ed729685147178540493ee8094e32-20210511 Received: from mtkmrs01.mediatek.inc [(172.21.131.159)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 525358072; Tue, 11 May 2021 19:46:06 +0800 Received: from MTKCAS06.mediatek.inc (172.21.101.30) by mtkmbs01n2.mediatek.inc (172.21.101.79) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 11 May 2021 19:46:04 +0800 Received: from localhost.localdomain (10.15.20.246) by MTKCAS06.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Tue, 11 May 2021 19:46:03 +0800 From: Rocco yue To: "David S . Miller" , Jakub Kicinski , Matthias Brugger CC: Andrew Morton , Masahiro Yamada , Nick Desaulniers , Andy Shevchenko , Peter Zijlstra , Tetsuo Handa , , , , , , Rocco Yue Subject: [PATCH][v3] rtnetlink: add rtnl_lock debug log Date: Tue, 11 May 2021 19:32:57 +0800 Message-ID: <20210511113257.2094-1-rocco.yue@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 X-MTK: N Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org From: Rocco Yue We often encounter system hangs caused by certain process holding rtnl_lock for a long time. Even if there is a lock detection mechanism in Linux, it is a bit troublesome and affects the system performance. We hope to add a lightweight debugging mechanism for detecting rtnl_lock. Up to now, we have discovered and solved some potential bugs through this lightweight rtnl_lock debugging mechanism, which is helpful for us. When you say Y for RTNL_LOCK_DEBUG, then the kernel will detect if any function hold rtnl_lock too long and some key information will be printed out to help locate the problem. i.e: from the following logs, we can clearly know that the pid=2206 RfxSender_4 process holds rtnl_lock for a long time, causing the system to hang. And we can also speculate that the delay operation may be performed in devinet_ioctl(), resulting in rtnl_lock was not released in time. [ 40.191481] rtnetlink: -- rtnl_print_btrace start -- [ 40.191494] rtnetlink: RfxSender_4[2206][R] hold rtnl_lock more than 2 sec, start time: 38181400013 [ 40.191571] Call trace: [ 40.191586] rtnl_print_btrace+0xf0/0x124 [ 40.191656] __delay+0xc0/0x180 [ 40.191663] devinet_ioctl+0x21c/0x75c [ 40.191668] inet_ioctl+0xb8/0x1f8 [ 40.191675] sock_do_ioctl+0x70/0x2ac [ 40.191682] sock_ioctl+0x5dc/0xa74 [ 40.191715] rtnetlink: -- rtnl_print_btrace end -- [ 42.181879] rtnetlink: rtnl_lock is held by [2206] from [38181400013] to [42181875177] Signed-off-by: Rocco Yue --- lib/Kconfig.debug | 10 ++++++ net/core/rtnetlink.c | 85 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 95 insertions(+) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 678c13967580..f1a722e16bee 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -2027,6 +2027,16 @@ config KCOV_IRQ_AREA_SIZE soft interrupts. This specifies the size of those areas in the number of unsigned long words. +config RTNL_LOCK_DEBUG + bool "rtnl_lock debugging, deadlock detection" + depends on STACKTRACE_SUPPORT + select STACKTRACE + help + If you say Y here then the kernel will detect whether any function + hold rtnl_lock too long and some key information will be printed + out to help locate the problem. + If unsure, say N. + menuconfig RUNTIME_TESTING_MENU bool "Runtime Testing" def_bool y diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 714d5fa38546..4f81086e5a42 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -12,6 +12,8 @@ * Vitaly E. Lavrov RTA_OK arithmetics was wrong. */ +#define pr_fmt(fmt) "rtnetlink: " fmt + #include #include #include @@ -57,6 +59,81 @@ #define RTNL_MAX_TYPE 50 #define RTNL_SLAVE_MAX_TYPE 40 +#ifdef CONFIG_RTNL_LOCK_DEBUG + +#include +#include + +/* Debug log and btrace will be printed when the rtnl_lock + * is held for more than RTNL_LOCK_MAX_HOLD_TIME seconds + */ +#define RTNL_LOCK_MAX_HOLD_TIME 2 + +#define RTNL_LOCK_MAX_TRACE 10 /* stack trace length */ + +struct rtnl_debug_btrace_t { + struct task_struct *task; + int pid; + unsigned long long start_time; + unsigned long long end_time; + unsigned long addrs[RTNL_LOCK_MAX_TRACE]; + unsigned int nr_entries; +}; + +static struct rtnl_debug_btrace_t rtnl_instance; + +static void rtnl_print_btrace(struct timer_list *unused); +static DEFINE_TIMER(rtnl_chk_timer, rtnl_print_btrace); + +/* Save stack trace to the given array of RTNL_LOCK_MAX_TRACE size. + */ +static int __save_stack_trace(unsigned long *trace) +{ + return stack_trace_save(trace, RTNL_LOCK_MAX_TRACE, 0); +} + +static void rtnl_get_btrace(struct task_struct *who) +{ + unsigned long expires; + + rtnl_instance.task = who; + rtnl_instance.pid = who->pid; + rtnl_instance.start_time = sched_clock(); + rtnl_instance.end_time = 0; + rtnl_instance.nr_entries = __save_stack_trace(rtnl_instance.addrs); + + expires = jiffies + RTNL_LOCK_MAX_HOLD_TIME * HZ; + mod_timer(&rtnl_chk_timer, expires); +} + +static void rtnl_print_btrace(struct timer_list *unused) +{ + pr_info("-- %s start --\n", __func__); + pr_info("%s[%d][%c] hold rtnl_lock more than %d sec, start time: %llu\n", + rtnl_instance.task->comm, + rtnl_instance.pid, + task_state_to_char(rtnl_instance.task), + RTNL_LOCK_MAX_HOLD_TIME, + rtnl_instance.start_time); + stack_trace_print(rtnl_instance.addrs, rtnl_instance.nr_entries, 0); + show_stack(rtnl_instance.task, NULL, KERN_INFO); + pr_info("-- %s end --\n", __func__); +} + +static void rtnl_relase_btrace(void) +{ + rtnl_instance.end_time = sched_clock(); + del_timer_sync(&rtnl_chk_timer); + + if (rtnl_instance.end_time - rtnl_instance.start_time > 2 * NSEC_PER_SEC) { + pr_info("rtnl_lock is held by [%d] from [%llu] to [%llu]\n", + rtnl_instance.pid, + rtnl_instance.start_time, + rtnl_instance.end_time); + } +} +#endif + struct rtnl_link { rtnl_doit_func doit; rtnl_dumpit_func dumpit; @@ -70,6 +147,10 @@ static DEFINE_MUTEX(rtnl_mutex); void rtnl_lock(void) { mutex_lock(&rtnl_mutex); + +#ifdef CONFIG_RTNL_LOCK_DEBUG + rtnl_get_btrace(current); +#endif } EXPORT_SYMBOL(rtnl_lock); @@ -95,6 +176,10 @@ void __rtnl_unlock(void) defer_kfree_skb_list = NULL; +#ifdef CONFIG_RTNL_LOCK_DEBUG + rtnl_relase_btrace(); +#endif + mutex_unlock(&rtnl_mutex); while (head) {