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 9D9FF401A16 for ; Thu, 30 Jul 2026 09:52:18 +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=1785405141; cv=none; b=Y5B1ANGypVAVf4nahcDcoachAYQqJIc6zDQVH+JinOI5G7Hl4SZahaCsQ56p/q0ZY7fD4v7ANJPJxID8RdjGch11F5sYxiOujZGmi6wr+6CbcMcHDjbz5CjCxB4L9Tp+4NwnC7xbxegtvMO8EcvdYXsuJ4+oQmZKwgo3bib1Adc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785405141; c=relaxed/simple; bh=WojzRvv0rXl+aW5k/hOdAbOV0JWZ8uhpq/hBBUd0a2Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aT9lxEC3bcjlJXQyufhGYDNPqFxOgKcJhXub8MtlblzSSVMhx++vNHm76QH44fTszmRw5wry2d5C48h0uNGzWqenlOquItQNXbE1hzv2NdI0bnXRey9KHstG/qZh533H5TDljDoi8etLaK8On2Oa0TmfXfDWu3L/73ClvDTT7go= 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=V5VrR53Z; 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="V5VrR53Z" 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=933/6+NI1BvuUYITK8haYrEa+juOdiNVKLbs63wan/U=; b=V5VrR53Z9jPjlaxWgLUKL93jch d3Hkec7BrPqbkBsvmnpsV6MBHKYCk5CTNsKpH76i+41wIwkKSNt3KAsI3ZUmw406UH52v63Q7d4mI zzvzP1hihuGqoopSso6WPJPpSXZsJSqcHCd6daKjeAsMjy0gVxNDXyO1QSB0GRnRi7bvdWQAlNDpm aYvGyBVNUvMVcpk/62SEyc9U1S3gWDc+5fDiyrvFqK1m5orBHu2jN1/P9+jCnwviytPqeFmWF0KaN KdvfGNDXp5AoDohs/wolvh0SExjbALOHnK60WLeYQhRTRzigC4pT20g3CuWZ7fU7vuBRNvid8t/9s Nd25SfjA==; 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 1wpNQv-00000006YNl-3Tzg; Thu, 30 Jul 2026 09:52:09 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id C1A04300EA1; Thu, 30 Jul 2026 11:52:08 +0200 (CEST) Date: Thu, 30 Jul 2026 11:52:08 +0200 From: Peter Zijlstra To: Andrea Righi Cc: Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Tejun Heo , Patrick Bellasi , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] sched: Fix SCHED_FLAG_KEEP_PARAMS side effects Message-ID: <20260730095208.GK49529@noisy.programming.kicks-ass.net> References: <20260730055011.2267333-1-arighi@nvidia.com> <20260730093224.GN49951@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: <20260730093224.GN49951@noisy.programming.kicks-ass.net> On Thu, Jul 30, 2026 at 11:32:24AM +0200, Peter Zijlstra wrote: > On Thu, Jul 30, 2026 at 07:50:09AM +0200, Andrea Righi wrote: > > SCHED_FLAG_KEEP_PARAMS allows sched_setattr() to update generic task > > attributes while retaining the task's existing scheduling parameters and > > class. > > Well, KEEP_PARAMS is only sensible when the policy is unchanged, but > that isn't in fact enforced. > > Do we want something like so to start with? > > --- > diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c > index b215b0ead9a6..48094923a755 100644 > --- a/kernel/sched/syscalls.c > +++ b/kernel/sched/syscalls.c > @@ -979,8 +979,11 @@ SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr, > if (!p) > return -ESRCH; > > - if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS) > + if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS) { > + if (attr.sched_policy != p->policy) Ah, it also needs to deal with SETPARAM_POLICY, so something like: attr.sched_policy != SETPARAM_POLICY && attr.sched_policy != p->policy I suppose. > + return -EINVAL; > get_params(p, &attr, 0); > + } > > return sched_setattr(p, &attr); > }