From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0190BC433F5 for ; Fri, 1 Oct 2021 15:50:23 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C1C1961A7D for ; Fri, 1 Oct 2021 15:50:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org C1C1961A7D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3E54F6EE2A; Fri, 1 Oct 2021 15:50:22 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7D5416EE2A; Fri, 1 Oct 2021 15:50:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=HAozprAp32k9vluNj0AhWzSv/u8RNIsE8GQbafTAqFI=; b=EjNsxX3QzNlfSlwpynUNG3XhQX ZDGss5O+cNt/k7rlRBE9UfxX6J5Il76R3cpedfqVBVUzUHVOmz0df5mzLhZJPsTAPjF4VswLYqVmS HokkwmLC6/pzbaicegAjcsnGx9QBWXhCdCAPxCzt9rmpd+AfhEchZSyC0ftj1SWNirudZFRmbTYBw uyj4m7xb18tt2JCceUU5ixGNI+ghnZHHdb1yo9DuezH62LjcAVNpnnmgHvtte2RePB3bPReoL50UU 2cj4T+VLNqMgSbuAXi53xSLVW/mpw/g1VXdGYBFwX3iKdfYduBR9gCzPxmY2hZx1iUpVIJwhcm5MB 605xK5ww==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mWKm1-00E2XF-V6; Fri, 01 Oct 2021 15:48:47 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id A9F95302A0E; Fri, 1 Oct 2021 17:48:32 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 57CE029ACCB62; Fri, 1 Oct 2021 17:48:32 +0200 (CEST) Date: Fri, 1 Oct 2021 17:48:32 +0200 From: Peter Zijlstra To: Tvrtko Ursulin Cc: Intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Tvrtko Ursulin , Ingo Molnar , Juri Lelli , Vincent Guittot Message-ID: References: <20210930171552.501553-1-tvrtko.ursulin@linux.intel.com> <20210930171552.501553-2-tvrtko.ursulin@linux.intel.com> <20210930183316.GC4323@worktop.programming.kicks-ass.net> <4aca656d-678f-4d61-38a4-d2e7a8fd89ab@linux.intel.com> <5c71ec04-9148-0587-c495-11dbd8f77d67@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5c71ec04-9148-0587-c495-11dbd8f77d67@linux.intel.com> Subject: Re: [Intel-gfx] [RFC 1/6] sched: Add nice value change notifier X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Fri, Oct 01, 2021 at 11:32:16AM +0100, Tvrtko Ursulin wrote: > > On 01/10/2021 10:04, Tvrtko Ursulin wrote: > > > > Hi Peter, > > > > On 30/09/2021 19:33, Peter Zijlstra wrote: > > > On Thu, Sep 30, 2021 at 06:15:47PM +0100, Tvrtko Ursulin wrote: > > > >   void set_user_nice(struct task_struct *p, long nice) > > > >   { > > > >       bool queued, running; > > > > -    int old_prio; > > > > +    int old_prio, ret; > > > >       struct rq_flags rf; > > > >       struct rq *rq; > > > > @@ -6913,6 +6945,9 @@ void set_user_nice(struct task_struct *p, > > > > long nice) > > > >        */ > > > >       p->sched_class->prio_changed(rq, p, old_prio); > > > > +    ret = atomic_notifier_call_chain(&user_nice_notifier_list, > > > > nice, p); > > > > +    WARN_ON_ONCE(ret != NOTIFY_DONE); > > > > + > > > >   out_unlock: > > > >       task_rq_unlock(rq, p, &rf); > > > >   } > > > > > > No, we're not going to call out to exported, and potentially unbounded, > > > functions under scheduler locks. > > > > Agreed, that's another good point why it is even more hairy, as I have > > generally alluded in the cover letter. > > > > Do you have any immediate thoughts on possible alternatives? > > > > Like for instance if I did a queue_work from set_user_nice and then ran > > a notifier chain async from a worker? I haven't looked at yet what > > repercussion would that have in terms of having to cancel the pending > > workers when tasks exit. I can try and prototype that and see how it > > would look. > > Hm or I simply move calling the notifier chain to after task_rq_unlock? That > would leave it run under the tasklist lock so probably still quite bad. Hmm? That's for normalize_rt_tasks() only, right? Just don't have it call the notifier in that special case (that's a magic sysrq thing anyway).