From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 28D4AB674 for ; Wed, 2 Apr 2025 18:16:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743617792; cv=none; b=NGHc2JABgCx6L1XRmmm+0+9OFUC/DntoGkXKVZH8WcUIZ2AsAHQRya+xjhqVUMz4g3UVdqGUooiSfQ5skefU7G7QN7XHl74dNC+DjNG6ypELboqcxgf0FEN5HaS2AgI+iODOcldqeYTTznM0aau8JYoj5TQtKyZ/Dqpx/Nze4mQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743617792; c=relaxed/simple; bh=w7PrYtRAx4c/uDv7ZWUo0w6QoO2+YwivCacOGOGF7i8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=s1ariz7HXwFxq0uYIsJfDsVjVANzamo6XraOFgAAjDbdkbq+/flxUJPyWkEqNIQ3s5acNy2wt0cuUM3ix72QTvoeQYkQzzMSzDULoYppQACIeY/gycnrLLeHw0Fad/PyUYEANKDp5dOgfXXVgkiyjAvX+XzPwp8HeoyRKCvBsEc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mouyiy9w; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mouyiy9w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8CAADC4CEDD; Wed, 2 Apr 2025 18:16:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743617791; bh=w7PrYtRAx4c/uDv7ZWUo0w6QoO2+YwivCacOGOGF7i8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mouyiy9wZJJsAr0LsAFR9W+IniWXifkNvjNqbpROb8gKjYi1IA37qE7nd+EofLFvz XmnFQoIa62Ea672CmZk6qoev3YtYz4czB/3rHHufWRs6ZYn5URJ/rEPatBfa3OotzT UwjmXfkMUwu2DW/XGCDON3T/B1bLGejdDMYpeSyQ11c5S3SBRS83tc6ddZaolGk8qY bLX32pgoWdmJMuL1iWNqZYCc6kUjBBwrodKSw8DfeJ9lsOPNk7+CHpNkFewf2yeMQ2 DWJFSAbSqqTDiu/tu8LoD8OLMKwtH2wu+Y/GPKHHuy/PUS7EDD2RC1ySkZBfW9l7DP Sr4jDkd64K/QA== Date: Wed, 2 Apr 2025 08:16:30 -1000 From: Tejun Heo To: Frederic Weisbecker Cc: Marco Crivellari , Sebastian Andrzej Siewior , open list , Lai Jiangshan , Thomas Gleixner Subject: Re: [PATCH] workqueue: Always use wq_select_unbound_cpu() for WORK_CPU_UNBOUND. Message-ID: References: <20250221112003.1dSuoGyc@linutronix.de> <20250226161847.eYrJFpIg@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hello, Frederic. On Wed, Apr 02, 2025 at 06:40:47PM +0200, Frederic Weisbecker wrote: > > If we're renaming, I'd deprecate the schedule_*() interface and always use > > queue_*() and maybe: > > > > - Replace WQ_UNBOUND with its complement WQ_PERCPU. > > This one scares us a bit. Currently the default for alloc_workqueue() is > WQ_PERCPU. After that the default will be the reverse. Even if this > happens as a single patch treewide change, there will be conflicts > in the merge window with new users coming up that will happen to be > unbound whenever they were not intended to. > > But there is a way out of that if we are patient: > > 1) For one release, do a treewide change that introduces WQ_PERCPU and apply > it to all relevant users. Keep WQ_UNBOUND around for now and warn if neither > WQ_PERCPU nor WQ_UNBOUND has been passed (this and grep/coccinelle will catch > missed patches from other trees after the merge window). > > 2) Once that complete, remove WQ_UNBOUND and its uses on the next release. > > How does that sound? Yeah, that sounds way safer. > > - Add WQ_PREFER_PERCPU. > > This can be done afterward case by case. > > > - Rename system_wq -> system_percpu_wq. > > - Add system_prefer_percpu_wq. > > - Rename system_unbound_wq -> system_dfl_wq. > > Easy steps. Sounds great to me. Thanks. -- tejun