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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68BDCC433EF for ; Mon, 17 Jan 2022 12:13:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F11586B0071; Mon, 17 Jan 2022 07:13:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EC2466B0073; Mon, 17 Jan 2022 07:13:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DAFB96B0074; Mon, 17 Jan 2022 07:13:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0246.hostedemail.com [216.40.44.246]) by kanga.kvack.org (Postfix) with ESMTP id C90A46B0071 for ; Mon, 17 Jan 2022 07:13:44 -0500 (EST) Received: from smtpin31.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 8874895CA9 for ; Mon, 17 Jan 2022 12:13:44 +0000 (UTC) X-FDA: 79039669968.31.63F6AC5 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) by imf16.hostedemail.com (Postfix) with ESMTP id 50A1F180007 for ; Mon, 17 Jan 2022 12:13:41 +0000 (UTC) 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=0xwjXHytdG9TW+eEv4h5HG046BJiyWLMcQrJvytddgc=; b=Pz8qepblptPdOh+nacvo2kZqQ4 1ITos2gLO+OPiB77uK7PkjNvo7oL9fZrE+gVFXl/EZjE0fcMaiuNDDZR+/mhn1jDamMHBX68xBPZP P1QvUSgvqMdcGkx60U3GHqCbO8uOdwurN8/WsCs0sTIey18EU6B+ACuqHIPrhVnY87KG+cJNTAegQ 1vO7/SjXM0Kv51kNUDzTMp5ysaC4X0YLehawm3MHYtqHk98oar1uNQWWLRst0Prx1WLzD0m2O1PLF mzkSome0hxLI/FCGZpTOZk2AJaqz0QPkKKgkCbgDGUnSbVfU2K+190bUlsEpAH+MLJ/u0BwG5WwhJ hBIqjnRQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1n9Qsd-001dpx-C8; Mon, 17 Jan 2022 12:12:59 +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 (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 775EA3001FD; Mon, 17 Jan 2022 13:12:57 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 387852027C5EF; Mon, 17 Jan 2022 13:12:57 +0100 (CET) Date: Mon, 17 Jan 2022 13:12:57 +0100 From: Peter Zijlstra To: Peter Oskolkov Cc: mingo@redhat.com, tglx@linutronix.de, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, x86@kernel.org, pjt@google.com, posk@google.com, avagin@google.com, jannh@google.com, tdelisle@uwaterloo.ca Subject: Re: [RFC][PATCH 3/3] sched: User Mode Concurency Groups Message-ID: References: <20211214204445.665580974@infradead.org> <20211214205358.701701555@infradead.org> <20211221171900.GA580323@dev-hv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 50A1F180007 X-Stat-Signature: d9k93e3ppah7dj1t8f5khhr9yfec138s Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=infradead.org header.s=desiato.20200630 header.b=Pz8qepbl; spf=none (imf16.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.92.199) smtp.mailfrom=peterz@infradead.org; dmarc=none X-HE-Tag: 1642421621-336801 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jan 14, 2022 at 03:09:55PM +0100, Peter Zijlstra wrote: > On Tue, Dec 21, 2021 at 05:19:00PM +0000, Peter Oskolkov wrote: > > > + /* > > > + * Workers will still block in umcg_notify_resume() before they can > > > + * consume their error, servers however need to get the error asap. > > > + * > > > + * Still, things might be unrecoverably screwy after this. Not our > > > + * problem. > > > > I think we should explicitly document the unrecoverable screwiness > > of errors here, so that the userspace proactively kills itself > > to avoid badness. The only reason that returning an error here is > > mildly preferable to just killing the task (we already do that > > in other places) is to give the userspace an opportunity to > > log an error, with more state/info than we can do here. > > Bah, I should've written a better comment, because I can't quite > remember the case I had in mind. Also, again from the LAZY patch, I > think we can actually do better in some of the cases here. > > Specifically, currently we'll enqueue on ::runnable_workers_ptr and fail > waking ::next_tid and leave it at that. While I think waking > ::server_tid in that case makes sense. > > I'll go prod at this. Is anybody actually planning to use ::next_tid for workers? My current thinking is that much of the problems here stem from that. Let me ponder more..