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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 67671C2D0A8 for ; Wed, 30 Sep 2020 07:52:05 +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 F0F8A2075F for ; Wed, 30 Sep 2020 07:52:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=suse.com header.i=@suse.com header.b="Yx+4OiWz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F0F8A2075F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 203C26E56D; Wed, 30 Sep 2020 07:52:04 +0000 (UTC) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by gabe.freedesktop.org (Postfix) with ESMTPS id 83D7189C3B; Tue, 29 Sep 2020 08:23:26 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1601367805; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=KFyfyEQCS1dcCR4BhfL+zwiQ3CuzyAy4x23tr+VkzjE=; b=Yx+4OiWzh8hL3oRWBVwsl7OoNxopUmSyQasLhmn1G1pwm5WeUKovPN8LH2bdOC7Tf1qJAG BQKht+ljEQ7JSXztBWuZ/SDej3VcAwduMW5YketNY8WVwtpxMMor30Pmo+P2rpxR7SkCAG TBCtVCqjpOLjck1NyY3qWCFDobpueAs= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0860EB2A1; Tue, 29 Sep 2020 08:23:25 +0000 (UTC) Date: Tue, 29 Sep 2020 10:23:24 +0200 From: Michal Hocko To: Daniel Vetter Subject: Re: [patch 00/13] preempt: Make preempt count unconditional Message-ID: <20200929081938.GC22035@dhcp22.suse.cz> References: <871rj4owfn.fsf@nanos.tec.linutronix.de> <87bli75t7v.fsf@nanos.tec.linutronix.de> <20200916152956.GV29330@paulmck-ThinkPad-P72> <20200916205840.GD29330@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Mailman-Approved-At: Wed, 30 Sep 2020 07:50:09 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juri Lelli , Peter Zijlstra , Sebastian Andrzej Siewior , Lai Jiangshan , dri-devel , Ben Segall , Linux-MM , "open list:KERNEL SELFTEST FRAMEWORK" , Will Deacon , Ard Biesheuvel , Anton Ivanov , linux-arch , Vincent Guittot , Herbert Xu , Brian Cain , linux-hexagon@vger.kernel.org, Russell King , Ingo Molnar , David Airlie , Ingo Molnar , Geert Uytterhoeven , Mel Gorman , Matt Turner , Valentin Schneider , linux-xtensa@linux-xtensa.org, Shuah Khan , "Paul E. McKenney" , Jeff Dike , intel-gfx , alpha , linux-um , Josh Triplett , Steven Rostedt , rcu@vger.kernel.org, linux-m68k , Ivan Kokshaysky , Rodrigo Vivi , Thomas Gleixner , Dietmar Eggemann , Linux ARM , Richard Henderson , Chris Zankel , Max Filippov , Linus Torvalds , LKML , Richard Weinberger , Mathieu Desnoyers , Andrew Morton , Daniel Bristot de Oliveira Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Message-ID: <20200929082324.8famVQB5auZveQpBwcIc-bLaXiTN4xv0cMhsg7igPNs@z> On Wed 16-09-20 23:43:02, Daniel Vetter wrote: > I can > then figure out whether it's better to risk not spotting issues with > call_rcu vs slapping a memalloc_noio_save/restore around all these > critical section which force-degrades any allocation to GFP_ATOMIC at did you mean memalloc_noreclaim_* here? > most, but has the risk that we run into code that assumes "GFP_KERNEL > never fails for small stuff" and has a decidedly less tested fallback > path than rcu code. Even if the above then please note that memalloc_noreclaim_* or PF_MEMALLOC should be used with an extreme care. Essentially only for internal memory reclaimers. It grants access to _all_ the available memory so any abuse can be detrimental to the overall system operation. Allocation failure in this mode means that we are out of memory and any code relying on such an allocation has to carefuly consider failure. This is not a random allocation mode. -- Michal Hocko SUSE Labs _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel