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 739AA10D14B4 for ; Mon, 30 Mar 2026 13:43:35 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1w7Ctr-0003DQ-7Y; Mon, 30 Mar 2026 09:43:27 -0400 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 1w7Ctp-0003Bs-2A for qemu-trivial@nongnu.org; Mon, 30 Mar 2026 09:43:25 -0400 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 1w7Ctn-0002PA-1d for qemu-trivial@nongnu.org; Mon, 30 Mar 2026 09:43:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1774878202; 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:in-reply-to:in-reply-to: references:references; bh=21ztP/JKNYyajacLTv2VZBb+x/ur9yFC74QVg7IQS08=; b=c86+KT+TabRAnvdQs/duM25UZBuhIqZbRaVbZHB+dggM/HDIoEh1bHLvsvWZ4j3mYaO33c f5mHHaTo1of3XFmvKGO8eG6HZO4jG7qbhHK4fUtMvg7xLqhbaeW//Prl1Pah7SE5IoYUtb Q1FVxd8XwfPxvJqoano+7yZZv8u/Q6Q= Received: from mx-prod-mc-08.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-411-cZtcrZr2O42gSgdUZws1ew-1; Mon, 30 Mar 2026 09:43:19 -0400 X-MC-Unique: cZtcrZr2O42gSgdUZws1ew-1 X-Mimecast-MFC-AGG-ID: cZtcrZr2O42gSgdUZws1ew_1774878197 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 06C1518002FD; Mon, 30 Mar 2026 13:43:17 +0000 (UTC) Received: from redhat.com (unknown [10.44.36.79]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 44B6C180035F; Mon, 30 Mar 2026 13:43:15 +0000 (UTC) Date: Mon, 30 Mar 2026 14:43:11 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Stepan Popov Cc: qemu-devel@nongnu.org, qemu-trivial@nongnu.org, Paolo Bonzini Subject: Re: [PATCH] thread-pool: signal condition variable while holding lock Message-ID: References: <20260330130104.85200-1-Stepan.Popov@kaspersky.com> MIME-Version: 1.0 In-Reply-To: <20260330130104.85200-1-Stepan.Popov@kaspersky.com> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-MFC-PROC-ID: AlldUPnRwkH_j-qlOwlkVMOiorsFBZLWWECElfpRrZQ_1774878197 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline 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: -5 X-Spam_score: -0.6 X-Spam_bar: / X-Spam_report: (-0.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.54, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=1, RCVD_IN_VALIDITY_RPBL_BLOCKED=1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-trivial-bounces+qemu-trivial=archiver.kernel.org@nongnu.org Sender: qemu-trivial-bounces+qemu-trivial=archiver.kernel.org@nongnu.org On Mon, Mar 30, 2026 at 04:01:04PM +0300, Stepan Popov wrote: > Move qemu_cond_signal() inside the critical section protected by pool->lock. > Signaling while holding the lock imposes more predictable scheduling behavior. > > Signed-off-by: Stepan Popov > --- > util/thread-pool.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/util/thread-pool.c b/util/thread-pool.c > index 8f8cb38d5c..8e55aefd07 100644 > --- a/util/thread-pool.c > +++ b/util/thread-pool.c > @@ -265,8 +265,8 @@ BlockAIOCB *thread_pool_submit_aio(ThreadPoolFunc *func, void *arg, > spawn_thread(pool); > } > QTAILQ_INSERT_TAIL(&pool->request_list, req, reqs); > - qemu_mutex_unlock(&pool->lock); > qemu_cond_signal(&pool->request_cond); > + qemu_mutex_unlock(&pool->lock); > return &req->common; > } Doesn't this order mean that when the signal wakes up the waiting thread, that thread will get temporarily re-blocked waiting for 'lock' to be released by the original thread too. 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 :|