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 4E0C4367292 for ; Thu, 30 Jul 2026 09:32:36 +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=1785403961; cv=none; b=Yln0u6hIjh5lnF1B76n4FwQJqXAR187/9vCYdLH3VaLVrJIJScnvuOOg9Hj68lWyEywT5kqudev31jYSZ2Gv9i0KRgrEaHugjAusm3Z7lcFKys5oZ5YpXx2+zTpz0gHlb2exFLgAR6M5TezLjjsYB8Ghgz7rD9TQ/y7zws2YlzM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785403961; c=relaxed/simple; bh=wAjpS3lDHR0a75r5D/3kYln0dj+qRzK0QEfhJyTsuDY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Nw/l6u+xNpRcPYuhD+ZrLXu5LA0SidyUR2/UtJ6Y6NfYwY3occj4lLlMeTcBChm8kqPXcn3Eypz+/jvbagNAN7grgnK+LThaO7Me6M8gVbSaD3HcEGkvaLbQ3skpyayglD3XkjvvZTP/d6U3uB0DTDlQFb4raoKnyyIyamU8OvE= 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=Pn3Oq2gF; 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="Pn3Oq2gF" 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=EYwX9fOXgmiSx20LGVnXNRj8ijecKNqIOuZW/gTAYcE=; b=Pn3Oq2gFdaKLZ8i8fZFc4npvH6 COuoi/C987wzhnTPVup+zKjGalPfojenmO4yUyhE4t0T97D/yzq7o3Rjr8TLTGgqY3PO2T5q/nXH7 vNuD2xtVgercRuFGqjJUgOxSJuu7F3vcFgocEmwklsm5rRUBNgeH1zrGPwaEy2axwyUaHLi/1xHRJ DgNlYCNzkbN8ZJ4K2NZ+AVllU5mkGtbGt81ViUeSTFegYWPj1NxYoIG7DDgoz6PqWEbaK0B0g0TzL ++bz5tnd9+qImQelXfZcROtX1dgujDFHM6r/cPwQMyzCDSYWXXcRrbaPa6VNj6p01UwS9A/CUVbv5 PWvsKDCQ==; 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 1wpN7q-00000006XPV-07E9; Thu, 30 Jul 2026 09:32:26 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 97D13300969; Thu, 30 Jul 2026 11:32:24 +0200 (CEST) Date: Thu, 30 Jul 2026 11:32:24 +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: <20260730093224.GN49951@noisy.programming.kicks-ass.net> References: <20260730055011.2267333-1-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: <20260730055011.2267333-1-arighi@nvidia.com> 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) + return -EINVAL; get_params(p, &attr, 0); + } return sched_setattr(p, &attr); }