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=-5.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS 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 C90D2C433E2 for ; Fri, 28 Aug 2020 09:07:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8949020776 for ; Fri, 28 Aug 2020 09:07:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598605629; bh=iJ29MQbverKkUXcy2t6xCo9ztoVcU48RgfAfleJOr/s=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=tt+et8MRuQ1ZNor1FDLay4ahr1Vxpxlz2JB5HXLTzYTX/+GdWM+YlBmpZoJngl0Az NKeUYwaeGGYcW9f575CiO4tEhy1Ou4Wh7E8CDxZzzo8bRFaunLK+YwdGdPS4OaAlUt iJVZQGMpyS/Rckh7+0yRAafpADDPNLQTc46NjfM8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728555AbgH1JHJ (ORCPT ); Fri, 28 Aug 2020 05:07:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:45062 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728016AbgH1JHI (ORCPT ); Fri, 28 Aug 2020 05:07:08 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 493062071B; Fri, 28 Aug 2020 09:07:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598605627; bh=iJ29MQbverKkUXcy2t6xCo9ztoVcU48RgfAfleJOr/s=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=sHOU5fS3eW+dkXh3hubsixQafbCFIeb1C1fi8ZpJ1lXPiGZyRfv/XBfYZRlHXGxej OZgGP+A/wy1jqDlMKbZB8R3dcWK8qb18wqqs7ib8GmeLrdF7mnOCFk6YidbK+2z5Bh mE+JLb+YzL8p2NXPen2uI8wj2pyksFsjyH74KdO8= Date: Fri, 28 Aug 2020 18:07:02 +0900 From: Masami Hiramatsu To: Masami Hiramatsu Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Eddy_Wu@trendmicro.com, x86@kernel.org, davem@davemloft.net, rostedt@goodmis.org, naveen.n.rao@linux.ibm.com, anil.s.keshavamurthy@intel.com, linux-arch@vger.kernel.org, cameron@moodycamel.com, oleg@redhat.com, will@kernel.org, paulmck@kernel.org Subject: Re: [RFC][PATCH 3/7] kprobes: Remove kretprobe hash Message-Id: <20200828180702.1e00c4e75e0f4b92fbc7b001@kernel.org> In-Reply-To: <20200828030059.d6618caf5b0214c424b941df@kernel.org> References: <20200827161237.889877377@infradead.org> <20200827161754.359432340@infradead.org> <20200828030059.d6618caf5b0214c424b941df@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Fri, 28 Aug 2020 03:00:59 +0900 Masami Hiramatsu wrote: > On Thu, 27 Aug 2020 18:12:40 +0200 > Peter Zijlstra wrote: > > > +static void invalidate_rp_inst(struct task_struct *t, struct kretprobe *rp) > > +{ > > + struct invl_rp_ipi iri = { > > + .task = t, > > + .rp = rp, > > + .done = false > > + }; > > + > > + for (;;) { > > + if (try_invoke_on_locked_down_task(t, __invalidate_rp_inst, rp)) > > + return; > > + > > + smp_call_function_single(task_cpu(t), __invalidate_rp_ipi, &iri, 1); > > + if (iri.done) > > + return; > > + } > > Hmm, what about making a status place holder and point it from > each instance to tell it is valid or not? > > struct kretprobe_holder { > atomic_t refcnt; > struct kretprobe *rp; > }; > > struct kretprobe { > ... > struct kretprobe_holder *rph; // allocate at register > ... > }; > > struct kretprobe_instance { > ... > struct kretprobe_holder *rph; // free if refcnt == 0 > ... > }; > > cleanup_rp_inst(struct kretprobe *rp) > { > rp->rph->rp = NULL; > } > > kretprobe_trampoline_handler() > { > ... > rp = READ_ONCE(ri->rph-rp); > if (likely(rp)) { > // call rp->handler > } else > rcu_call(ri, free_rp_inst_rcu); > ... > } > > free_rp_inst_rcu() > { > if (!atomic_dec_return(ri->rph->refcnt)) > kfree(ri->rph); > kfree(ri); > } > > This increase kretprobe_instance a bit, but make things simpler. > (and still keep lockless, atomic op is in the rcu callback). OK, I've written the code and run a smoke test on it. I'll send it with my 4th version of series. Thank you, -- Masami Hiramatsu