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.gnu.org (lists.gnu.org [209.51.188.17]) (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 1B0BBE9A03B for ; Wed, 18 Feb 2026 10:45:41 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vsf3n-0000R6-Eu; Wed, 18 Feb 2026 05:45:35 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vsf3f-0000Pw-9Y for qemu-rust@nongnu.org; Wed, 18 Feb 2026 05:45:27 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vsf3b-0002nH-FR for qemu-rust@nongnu.org; Wed, 18 Feb 2026 05:45:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1771411520; h=from:from:reply-to: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; bh=1daQWUYdxPH0U39GJiqxU0N0Xk6rs2qulmWoOgh/mOo=; b=K32nqNEB9odnFaPz6vmR6A8xQZ+bxB6cXb20WNpdtl+NngfawVMgG1ZSuRGMYCntFS2cOV 07pRv8/Ms9UTxewesmtnF/DhgTdCQa0rgkPrEMJpQnwGPuIiB2l2+UO5XjVeLbOV6H6KkC oplaNWv8nH3Wkg4RMHsd+oRSHzlcZ1c= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-93-laaogyxCOISg7a4gQKmong-1; Wed, 18 Feb 2026 05:45:17 -0500 X-MC-Unique: laaogyxCOISg7a4gQKmong-1 X-Mimecast-MFC-AGG-ID: laaogyxCOISg7a4gQKmong_1771411516 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5CCCA1800282; Wed, 18 Feb 2026 10:45:15 +0000 (UTC) Received: from redhat.com (unknown [10.45.224.150]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7E7BA19560B5; Wed, 18 Feb 2026 10:45:09 +0000 (UTC) Date: Wed, 18 Feb 2026 10:45:05 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Cc: qemu-devel@nongnu.org, Manos Pitsidianakis , Stefan Weil , "Dr. David Alan Gilbert" , Pierrick Bouvier , devel@lists.libvirt.org, Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Hanna Reitz , Kevin Wolf , qemu-block@nongnu.org, qemu-rust@nongnu.org, Paolo Bonzini , Gerd Hoffmann , Christian Schoenebeck , Richard Henderson Subject: Re: [PATCH v6 12/27] util: avoid repeated prefix on incremental qemu_log calls Message-ID: References: <20260211152508.732487-1-berrange@redhat.com> <20260211152508.732487-13-berrange@redhat.com> <87ms16e5vc.fsf@pond.sub.org> MIME-Version: 1.0 In-Reply-To: <87ms16e5vc.fsf@pond.sub.org> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-MFC-PROC-ID: N6u_X4Cl5b6IH0EYUE8y7XIH_At_0UufJOrZzpwyISA_1771411516 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -13 X-Spam_score: -1.4 X-Spam_bar: - X-Spam_report: (-1.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.043, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, GB_FAKE_RF=0.754, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-rust@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: QEMU Rust-related patches and discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-rust-bounces+qemu-rust=archiver.kernel.org@nongnu.org Sender: qemu-rust-bounces+qemu-rust=archiver.kernel.org@nongnu.org On Wed, Feb 18, 2026 at 10:52:07AM +0100, Markus Armbruster wrote: > Daniel P. Berrangé writes: > > > There are three general patterns to QEMU log output > > > > 1. Single complete message calls > > > > qemu_log("Some message\n"); > > > > 2. Direct use of fprintf > > > > FILE *f = qemu_log_trylock() > > fprintf(f, "..."); > > fprintf(f, "..."); > > fprintf(f, "...\n"); > > qemu_log_unlock(f) > > Real code needs to check @f or risk crashing. Shouldn't we show that > here? Yes, we should really. > > 3. Mixed use of qemu_log_trylock/qemu_log() > > > > FILE *f = qemu_log_trylock() > > qemu_log("...."); > > qemu_log("...."); > > qemu_log("....\n"); > > qemu_log_unlock(f) > > > > When message prefixes are enabled, the timestamp will be > > unconditionally emitted for all qemu_log() calls. This > > works fine in the 1st case, and has no effect in the 2nd > > case. In the 3rd case, however, we get the timestamp > > printed over & over in each fragment. > > > > One can suggest that pattern (3) is pointless as it is > > functionally identical to (2) but with extra indirection > > and overhead. None the less we have a fair bit of code > > that does this. > > > > The qemu_log() call itself is nothing more than a wrapper > > which does pattern (2) with a single fprintf() call. > > qemu_log_trylock()'s lock is recursive. Worth a comment? Not sure. Sure. > > Fixes: 012842c07552 (log: make '-msg timestamp=on' apply to all qemu_log usage) > > Reported-by: Richard Henderson > > Signed-off-by: Daniel P. Berrangé > > Reviewed-by: Markus Armbruster > With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|