From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 CDB3C455176; Thu, 10 Sep 2026 10:38:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789036712; cv=none; b=MPv7IqTPyM9n1bW+LwMThvCGUp+uZzFqs6zgs1hRV2INFfWjsUD41U/uReE2vgStu4lNAg22vWDD4J5t8TNG4Ufbho0yecfuB8HuRUry9jxz7L1XjLfcAFv8Vt6QCGCGO/puut4uGileW2H85NecS28QxguG+cF1O17T/BepvZQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789036712; c=relaxed/simple; bh=6vnFr65x8+MgNoAd6e1I2W0+ljuPVyeuH7FB4u4TqPE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=CQfh0tFdVLSLR3/sl5Z4BLulIfS408cgSR7wlMTIH7WH+D44npi9BPVYc7CzSS6reoPsj+QACJmvCmSxg5ajEHiVK2Butn7NywE1w0u+N6ACiAwU/yJjtcSZaSh4bOsnn1XLDEeSRNamdBX+BjivwxffIFa6W658Azu68YccOd4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=m3IDpAg2; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="m3IDpAg2" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=8r6IyBpcLFd8eGwMl+s54hpnssHIQXxQVO6P+3A6Prw=; b=m3IDpAg2cgu9vNfEQuM6yRy89t AN7pCCLryAK2Kk0m6xGaKH16hg/sCyUyemYjV5junlTsQHHkRGF09Bm63B3T9lvAJlKNx9rtqSfIj UHTuxpejXUxqjsDHDuxPNAednXrfqq2h/hueZhJB0Cw3Y3Jm1Lbrby7DTDYg5iB47O3vw032RN8aQ +C7ZgnysoKl/BQKba0UyHjTF748+/1haYQyGQFRLIE1WHg/paNVAF+LeYBVzIOnGJxIBqYDFq28E9 FcSNFv5QmsrXAwz/Sd2wRIIY00GAcMgE/77nMph25oU03jsO3et0Rz5sGm5gmM3B1h4D5CLfbvHR7 P3Lk/PFw==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.2 #2 (Red Hat Linux)) id 1x4cAd-00000002LAx-3QFs; Thu, 10 Sep 2026 10:38:19 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 60A4B30056B; Thu, 10 Sep 2026 12:38:18 +0200 (CEST) Date: Thu, 10 Sep 2026 12:38:18 +0200 From: Peter Zijlstra To: Andrea Righi Cc: Tejun Heo , David Vernet , Changwoo Min , John Stultz , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Christian Loehle , David Dai , Emil Tsalapatis , Lee Trager , Richard Cheng , Koba Ko , Aiqun Yu , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH 07/18] sched: Add sched_ext hooks for proxy execution Message-ID: <20260910103818.GH4120091@noisy.programming.kicks-ass.net> References: <20260831134338.1531664-1-arighi@nvidia.com> <20260831134338.1531664-8-arighi@nvidia.com> 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: <20260831134338.1531664-8-arighi@nvidia.com> On Mon, Aug 31, 2026 at 03:42:17PM +0200, Andrea Righi wrote: > Proxy execution splits the scheduling context (the donor) from the > execution context (the lock owner). sched_ext needs to observe that > split at three points in __schedule(): > > - whether a blocked EXT task can be retained on the runqueue as a > donor, > - when a donor's scheduling context starts driving a lock owner, > - once proxy resolution has settled for the current pick. > > Introduce scx_allow_proxy_exec(), scx_proxy_donor_start() and > scx_proxy_resolved(), and add their call sites in __schedule(). The > implementations are empty here and are filled in by the sched_ext > changes that follow, so that all the sched core changes needed by proxy > execution stay together in the preparatory patches. > > SCHED_PROXY_EXEC still depends on !SCHED_CLASS_EXT, so the new hooks are > inert: they are compiled out with CONFIG_SCHED_CLASS_EXT=n and > unreachable otherwise. > > This is a preparatory change to support proxy execution with sched_ext. > No functional change. > > Signed-off-by: Andrea Righi > --- > kernel/sched/core.c | 12 +++++++----- > kernel/sched/ext/ext.c | 13 +++++++++++++ > kernel/sched/ext/ext.h | 6 ++++++ > 3 files changed, 26 insertions(+), 5 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index bb79fcfa21cd2..d578dd635f2eb 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -7217,13 +7217,12 @@ static void __sched notrace __schedule(int sched_mode) > } > } else if (!preempt && prev_state) { > /* > - * We pass task_is_blocked() as the should_block arg > - * in order to keep mutex-blocked tasks on the runqueue > - * for slection with proxy-exec (without proxy-exec > - * task_is_blocked() will always be false). > + * Keep mutex-blocked tasks on the runqueue for proxy execution > + * only when their scheduling class allows it. Without proxy > + * execution, task_is_blocked() always returns false. > */ > try_to_block_task(rq, prev, &prev_state, > - !task_is_blocked(prev)); > + !task_is_blocked(prev) || !scx_allow_proxy_exec(prev)); > switch_count = &prev->nvcsw; > } > > @@ -7244,6 +7243,7 @@ static void __sched notrace __schedule(int sched_mode) > } > if (next == rq->idle) { > zap_balance_callbacks(rq); > + scx_proxy_resolved(rq); > goto keep_resched; > } > } > @@ -7264,6 +7264,8 @@ static void __sched notrace __schedule(int sched_mode) > donor->sched_class->put_prev_task(rq, donor, donor); > donor->sched_class->set_next_task(rq, donor, true); > } > + scx_proxy_donor_start(rq); > + scx_proxy_resolved(rq); > } else { > rq_set_donor(rq, next); > } Can you expand on the need for scx_proxy_resolved() ? I understand the other two, but this one I'm struggling with a bit.