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=-11.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 25FE5C433E7 for ; Mon, 19 Oct 2020 20:00:33 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 66415222B8 for ; Mon, 19 Oct 2020 20:00:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Um57Vndk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 66415222B8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=tempfail smtp.mailfrom=dm-devel-bounces@redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603137630; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=RcFVJ6gymnWhNwStp/FXUQ6tBxtiLw6TBPWS9L56DCc=; b=Um57VndkYFNEqbrdj5HZyRyXEEhsYhxbl5VdBQN9HA8UzrajppaEXG7btUqbqxqOFP1PI2 +GU4czW/Ph1m3sXYKVXhyeJjgHz3dVXuI6OmR7PWPKepntlrTNttKBwGNMRmoMLJGTPMw/ Ta+5tJuxrGqDIgYIHaVW/G6rMGrakLs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-108-CUt5Q1BtP_qLH4stzxVAJg-1; Mon, 19 Oct 2020 16:00:27 -0400 X-MC-Unique: CUt5Q1BtP_qLH4stzxVAJg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DD4848049C9; Mon, 19 Oct 2020 20:00:22 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4518010013D0; Mon, 19 Oct 2020 20:00:22 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 6BCF6181A06B; Mon, 19 Oct 2020 20:00:20 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 09JK0IOv028605 for ; Mon, 19 Oct 2020 16:00:18 -0400 Received: by smtp.corp.redhat.com (Postfix) id CCBAD5D9EF; Mon, 19 Oct 2020 20:00:18 +0000 (UTC) Received: from octiron.msp.redhat.com (octiron.msp.redhat.com [10.15.80.209]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 22C865D9D2; Mon, 19 Oct 2020 20:00:15 +0000 (UTC) Received: from octiron.msp.redhat.com (localhost.localdomain [127.0.0.1]) by octiron.msp.redhat.com (8.14.9/8.14.9) with ESMTP id 09JK0DTo013939; Mon, 19 Oct 2020 15:00:13 -0500 Received: (from bmarzins@localhost) by octiron.msp.redhat.com (8.14.9/8.14.9/Submit) id 09JK0CTY013938; Mon, 19 Oct 2020 15:00:12 -0500 Date: Mon, 19 Oct 2020 15:00:12 -0500 From: Benjamin Marzinski To: mwilck@suse.com Message-ID: <20201019200012.GE3384@octiron.msp.redhat.com> References: <20201016104501.8700-1-mwilck@suse.com> <20201016104501.8700-19-mwilck@suse.com> MIME-Version: 1.0 In-Reply-To: <20201016104501.8700-19-mwilck@suse.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-loop: dm-devel@redhat.com Cc: lixiaokeng@huawei.com, dm-devel@redhat.com Subject: Re: [dm-devel] [PATCH v2 18/29] libmultipath: fix log_thread startup and teardown X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Fri, Oct 16, 2020 at 12:44:50PM +0200, mwilck@suse.com wrote: > From: Martin Wilck > > This fixes several issues with the log_thread. First, the running > flag logq_running should be set by the thread itself, not by > log_thread_start()/_stop(). Second, the thread was both cancelled and > terminated via a flag (again, logq_running). It's sufficient, > and better, to just cancel it and use logq_running as indication for > successful termination. Third, the locking wasn't cancel-safe in some > places. Forth, log_thread_start() and log_thread_stop() didn't wait for > startup/teardown properly. Fifth, using (pthread_t)0 is wrong (pthread_t is > opaque; there's no guarantee that 0 is not a valid pthread_t value). Sixth, > pthread_cancel() was called under logq_lock, which doesn't make sense to > me at all. > > Signed-off-by: Martin Wilck > --- > libmultipath/log_pthread.c | 72 ++++++++++++++++++++++++++------------ > 1 file changed, 49 insertions(+), 23 deletions(-) > > diff --git a/libmultipath/log_pthread.c b/libmultipath/log_pthread.c > index 0c327ff..3c73941 100644 > --- a/libmultipath/log_pthread.c > +++ b/libmultipath/log_pthread.c > @@ -13,6 +13,7 @@ > #include "log_pthread.h" > #include "log.h" > #include "lock.h" > +#include "util.h" > > static pthread_t log_thr; > > @@ -56,44 +57,70 @@ static void flush_logqueue (void) > } while (empty == 0); > } > > +static void cleanup_log_thread(__attribute((unused)) void *arg) > +{ > + logdbg(stderr, "log thread exiting"); > + pthread_mutex_lock(&logev_lock); > + logq_running = 0; > + pthread_mutex_unlock(&logev_lock); > +} > + > static void * log_thread (__attribute__((unused)) void * et) > { > int running; > > pthread_mutex_lock(&logev_lock); > - logq_running = 1; > + running = logq_running; > + if (!running) > + logq_running = 1; > + pthread_cond_signal(&logev_cond); > pthread_mutex_unlock(&logev_lock); > + if (running) > + /* already started */ > + return NULL; > + pthread_cleanup_push(cleanup_log_thread, NULL); > > mlockall(MCL_CURRENT | MCL_FUTURE); > logdbg(stderr,"enter log_thread\n"); > > while (1) { > pthread_mutex_lock(&logev_lock); > - if (logq_running && !log_messages_pending) > + pthread_cleanup_push(cleanup_mutex, &logev_lock); > + while (!log_messages_pending) > + /* this is a cancellation point */ > pthread_cond_wait(&logev_cond, &logev_lock); > log_messages_pending = 0; > - running = logq_running; > - pthread_mutex_unlock(&logev_lock); > - if (!running) > - break; > + pthread_cleanup_pop(1); > + > flush_logqueue(); > } > + pthread_cleanup_pop(1); > return NULL; > } > > void log_thread_start (pthread_attr_t *attr) > { > - logdbg(stderr,"enter log_thread_start\n"); > + bool err = false; > > - pthread_mutex_init(&logq_lock, NULL); > - pthread_mutex_init(&logev_lock, NULL); > - pthread_cond_init(&logev_cond, NULL); If you remove these initializers, then these variables are uninitialized. I realize that patch 29 makes them statically initialized, so I'm not sure how big of an issue it is. I guess it depends on how much we care about the possiblity of things not working right when bisecting an issue. -Ben > + logdbg(stderr,"enter log_thread_start\n"); > > if (log_init("multipathd", 0)) { > fprintf(stderr,"can't initialize log buffer\n"); > exit(1); > } > + > + pthread_mutex_lock(&logev_lock); > + pthread_cleanup_push(cleanup_mutex, &logev_lock); > if (pthread_create(&log_thr, attr, log_thread, NULL)) { > + err = true; > + } > + > + /* wait for thread startup */ > + while (!logq_running) > + pthread_cond_wait(&logev_cond, &logev_lock); > + pthread_cleanup_pop(1); > + > + if (err) { > fprintf(stderr,"can't start log thread\n"); > exit(1); > } > @@ -112,27 +139,26 @@ void log_thread_reset (void) > > void log_thread_stop (void) > { > + int running; > + > if (!la) > return; > > logdbg(stderr,"enter log_thread_stop\n"); > > pthread_mutex_lock(&logev_lock); > - logq_running = 0; > - pthread_cond_signal(&logev_cond); > - pthread_mutex_unlock(&logev_lock); > - > - pthread_mutex_lock(&logq_lock); > - pthread_cancel(log_thr); > - pthread_mutex_unlock(&logq_lock); > - pthread_join(log_thr, NULL); > - log_thr = (pthread_t)0; > + pthread_cleanup_push(cleanup_mutex, &logev_lock); > + running = logq_running; > + if (running) { > + pthread_cancel(log_thr); > + pthread_cond_signal(&logev_cond); > + } > + pthread_cleanup_pop(1); > > - flush_logqueue(); > + if (running) > + pthread_join(log_thr, NULL); > > - pthread_mutex_destroy(&logq_lock); > - pthread_mutex_destroy(&logev_lock); > - pthread_cond_destroy(&logev_cond); > > + flush_logqueue(); > log_close(); > } > -- > 2.28.0 -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel