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 2DAA22E0901; Wed, 29 Oct 2025 15:12:00 +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=1761750721; cv=none; b=DgL1GI+JbTL4LhueTrobvHFj8iZtutj9ghJMQ7u4yXk2mTQSyZtZUHu7aFCdMXz4i2p7pYKAairD0RIRElXEbiLAD0zEdo9BybxyV8m6wad0ftk7WWAOBDt5bgJGepaecrBT/I6IJlzusZJdWQqQO59IsAboqDTrl6mflI7TmsE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761750721; c=relaxed/simple; bh=p8U6eXtI/y0u8cy9tTh7hEYJQEBjW65osHVr+rdqzWg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZLSnMF/9Q6CC+c4gZ/L9XvYeitrxAvGukt3X5IyYVMk777rKJUzkASA3pkF9SiQ6Hq9UxO6ACjCkFQu5CkVEfLVMdWLHdOeJTQ/GW3Ji25WII+WimYPej2/DoM+uR7R+8MP442psWnMjrMeCj67uz9iG+A2xXcKtFIVfgs1CPvM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HLt0YjKm; 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="HLt0YjKm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AD200C4CEF8; Wed, 29 Oct 2025 15:11:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761750720; bh=p8U6eXtI/y0u8cy9tTh7hEYJQEBjW65osHVr+rdqzWg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HLt0YjKmQFILafJC1zKCzuWAUUICI6A6dIdS2d466CrL7PEQdgF4YdrDAew6Pvj9B lZ80XrAO/w4o/fBxWPzU5c+Zz3LQiQBhpDsbSHtzrCjCmZ6mWQTi09aicjZ4jHcI30 ffvkOncJJqck/hJC0P5cWSBMWUntfvmnTzp6GMAweZ4vp7Mnax+Aeu036V3THPBRbs qn0QpmUnZ1QSSV6uWgQgP0uc7PT5QMq9Ct4llmFNCeADlC72LjAZiIero7T9DDeGoj 0RtrmQhQ9juf4Rj2yA8KWP964OAU56VU6Yi33fMpoBxK8HLiOHg4XTrERvuEr3Jwg2 NK7tR5ihak31w== Date: Wed, 29 Oct 2025 05:11:58 -1000 From: Tejun Heo To: Peter Zijlstra Cc: David Vernet , Andrea Righi , Changwoo Min , linux-kernel@vger.kernel.org, sched-ext@lists.linux.dev, Wen-Fang Liu Subject: Re: [PATCH v2 3/3] sched_ext: Allow scx_bpf_reenqueue_local() to be called from anywhere Message-ID: References: <20251025001849.1915635-1-tj@kernel.org> <20251025001849.1915635-4-tj@kernel.org> <20251029104546.GI3419281@noisy.programming.kicks-ass.net> 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: <20251029104546.GI3419281@noisy.programming.kicks-ass.net> Hello, On Wed, Oct 29, 2025 at 11:45:46AM +0100, Peter Zijlstra wrote: > On Mon, Oct 27, 2025 at 08:19:40AM -1000, Tejun Heo wrote: > > The ops.cpu_acquire/release() callbacks are broken - they miss events under > > multiple conditions and can't be fixed without adding global sched core hooks > > that sched maintainers don't want. > > I think I'll object to that statement just a wee bit. I think we can > make it work -- just not with the things proposed earlier. Sure, I'll massage it a bit before committing. > Anyway, if you want to reduce the sched_ext interface and remove > cpu_acquire/release entirely, this is fine too. > > I might still do that wakeup_preempt() change if I can merge / replace > the queue_mask RETRY_TASK logic -- I have vague memories the RT people > also wanted something like this a while ago and it isn't that big of a > change. Yeah, being able to create some kind of interlocking from ttwu to pick_task is something generally useful, I think, even if I don't use it right now. > 6.23 is a long time, can't we throw this out quicker? This thing wasn't > supposed to be an ABI after all. A 1 release cycle seems fine to me ;-) We've been discussing about compat policy lately and I think what we landed on was maintaining compatibility, when reasonably possible, over one LTS release + a couple non-LTS releases, which comes out to ~1.5 to 2 years. That seems to give most people enough sliding room while not choking us with too much compat overhead. This is a bit more work but it is actually surprisingly not that painful with all the BPF compat features, and seems to hit a reasonable balance. Thanks. -- tejun