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 Received: from lists.lttng.org (lists.lttng.org [167.114.26.123]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D8F96C433EF for ; Tue, 14 Jun 2022 14:19:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=lists.lttng.org; s=default; t=1655216396; bh=4za8tjTTfGB/X46eReIHxFpW5hGYMP13YGVlrmAXdaI=; h=Date:To:Cc:In-Reply-To:References:Subject:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From:Reply-To:From; b=Dq0k908iP/u+ei54X+MGxd7bwTuG5I+tifxhixlNcxdGadd7wGy8y1ZZJn4n6Wtj3 9e/9GQm8r+QjQPOQIqHFkN2NPn+l57tvk2ddQR6O3MRa7V6skP1h1kTv5faLdXaoKM 7dIQCI6LTJLUpzAEGdXvpAkU0mEXB33U/icXD0Z3eY5K5+pZ2xdeCDphfRe+EgD+a2 jLs4l+76LGLnkg8pJiTsO+PzM0PxZQBEkvYJ5dzHouRJy0op0Lt11HCtkHQ1I00pGs GZmEujYP1S7ksQidwemBCCWsvsDdPAHDQzyGq+S2ADbgDC/3PqtHotm1r03dzHgFIQ BxqNFdLj3e71A== Received: from lists-lttng01.efficios.com (localhost [IPv6:::1]) by lists.lttng.org (Postfix) with ESMTP id 4LMrDX0Gqnz88X; Tue, 14 Jun 2022 10:19:56 -0400 (EDT) Received: from mail.efficios.com (mail.efficios.com [167.114.26.124]) by lists.lttng.org (Postfix) with ESMTPS id 4LMrDW1Fqvz8TF for ; Tue, 14 Jun 2022 10:19:54 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id B0FB43C67C8 for ; Tue, 14 Jun 2022 10:19:54 -0400 (EDT) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id zuh4gM4ahptd; Tue, 14 Jun 2022 10:19:54 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 58A113C67C7; Tue, 14 Jun 2022 10:19:54 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 58A113C67C7 X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id jN6wwz7m6opL; Tue, 14 Jun 2022 10:19:54 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id 4E06A3C67B6; Tue, 14 Jun 2022 10:19:54 -0400 (EDT) Date: Tue, 14 Jun 2022 10:19:54 -0400 (EDT) To: Minlan Wang Cc: lttng-dev Message-ID: <1389308213.59040.1655216394223.JavaMail.zimbra@efficios.com> In-Reply-To: <20220614035533.GA174967@localhost.localdomain>+C23B4245BB527E95> References: <20220614035533.GA174967@localhost.localdomain> MIME-Version: 1.0 X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_4272 (ZimbraWebClient - FF100 (Linux)/8.8.15_GA_4257) Thread-Topic: urcu workqueue thread uses 99% of cpu while workqueue is empty Thread-Index: QwgfFyVxBy9wNzVzv74Jesiw6xDQkw== Subject: Re: [lttng-dev] urcu workqueue thread uses 99% of cpu while workqueue is empty X-BeenThere: lttng-dev@lists.lttng.org X-Mailman-Version: 2.1.39 Precedence: list List-Id: LTTng development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Mathieu Desnoyers via lttng-dev Reply-To: Mathieu Desnoyers Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: lttng-dev-bounces@lists.lttng.org Sender: "lttng-dev" ----- On Jun 13, 2022, at 11:55 PM, Minlan Wang wangminlan@szsandstone.com wrote: > Hi, Mathieu, > We are running a CentOS 8.2 os on Intel(R) Xeon(R) CPU E5-2630 v4, Also, can you provide more information about which exact Linux kernel version you are using ? Thanks, Mathieu > and using the workqueue interfaces in src/workqueue.h in > userspace-rcu-latest-0.12.tar.bz2. > Recently, we found the workqueue thread rushes cpu into 99% usage. > After some debuging, we found that the futex in struct urcu_workqueue got > into very big negative value, e.g, -12484; while the qlen, cbs_tail, and > cbs_head suggest that the workqueue is empty. > We add a watchpoint of workqueue->futex in workqueue_thread(), and got this > log when workqueue->futex first get into -2: > ... > Old value = -1 > New value = 0 > 0x00007ffff37c1d6d in futex_wake_up (futex=0x55555f74aa40) at workqueue.c:160 > 160 in workqueue.c > #0 0x00007ffff37c1d6d in futex_wake_up (futex=0x55555f74aa40) at > workqueue.c:160 > #1 0x00007ffff37c2737 in wake_worker_thread (workqueue=0x55555f74aa00) at > workqueue.c:324 > #2 0x00007ffff37c29fb in urcu_workqueue_queue_work (workqueue=0x55555f74aa00, > work=0x555566e05e00, func=0x7ffff7523c90 ) at > workqueue.c:3 > 67 > #3 0x00007ffff752c520 in aio_complete_cb (ctx=, > iocb=, res=, res2=) at > bio/aio_bio_adapter.c:152 > #4 0x00007ffff752c696 in poll_io_complete (arg=0x555562e4f4a0) at > bio/aio_bio_adapter.c:289 > #5 0x00007ffff72e6ea5 in start_thread () from /usr/lib64/libpthread.so.0 > #6 0x00007ffff415d96d in clone () from /usr/lib64/libc.so.6 > [Switching to Thread 0x7fffde3f3700 (LWP 821768)] > Hardware watchpoint 4: -location workqueue->futex > > Old value = 0 > New value = -1 > 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at > ../include/urcu/uatomic.h:490 > 490 ../include/urcu/uatomic.h: No such file or directory. > #0 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at > ../include/urcu/uatomic.h:490 > #1 workqueue_thread (arg=0x55555f74aa00) at workqueue.c:250 > #2 0x00007ffff72e6ea5 in start_thread () from /usr/lib64/libpthread.so.0 > #3 0x00007ffff415d96d in clone () from /usr/lib64/libc.so.6 > Hardware watchpoint 4: -location workqueue->futex > > Old value = -1 > New value = -2 > 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at > ../include/urcu/uatomic.h:490 > 490 in ../include/urcu/uatomic.h > #0 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at > ../include/urcu/uatomic.h:490 > #1 workqueue_thread (arg=0x55555f74aa00) at workqueue.c:250 > #2 0x00007ffff72e6ea5 in start_thread () from /usr/lib64/libpthread.so.0 > #3 0x00007ffff415d96d in clone () from /usr/lib64/libc.so.6 > Hardware watchpoint 4: -location workqueue->futex > > Old value = -2 > New value = -3 > 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at > ../include/urcu/uatomic.h:490 > 490 in ../include/urcu/uatomic.h > #0 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at > ../include/urcu/uatomic.h:490 > #1 workqueue_thread (arg=0x55555f74aa00) at workqueue.c:250 > #2 0x00007ffff72e6ea5 in start_thread () from /usr/lib64/libpthread.so.0 > #3 0x00007ffff415d96d in clone () from /usr/lib64/libc.so.6 > Hardware watchpoint 4: -location workqueue->futex > ... > > After this, things went into wild, workqueue->futex got into bigger negative > value, and workqueue thread eat up the cpu it is using. > This ends only when workqueue->futex down flew into 0. > > Do you have any idea why this is happening, and how to fix it? > > B.R > Minlan Wang -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev