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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 4AFA2C282CE for ; Mon, 11 Feb 2019 13:52:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 19A41222B1 for ; Mon, 11 Feb 2019 13:52:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="hVozEyWS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728320AbfBKNwH (ORCPT ); Mon, 11 Feb 2019 08:52:07 -0500 Received: from merlin.infradead.org ([205.233.59.134]:42362 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727472AbfBKNwH (ORCPT ); Mon, 11 Feb 2019 08:52:07 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; 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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=eWj3rusOmVs9VU5WrUyV3EmRPWyzvShi15z9JJNii/c=; b=hVozEyWSFnyoOUQcnRc2RCaV3 0J398ZZndorxm7wOPboATWk4jdD5UWzPHAioDvqYGGE0Wjv9fM0yM2c5HYQNuYcN9JCUMghQbSGAG 27EkDEEZ5evdFr/qh4DMiB+hDqXvw0NKCvIJ8mOuy8AI0Z3kasJTwW4aiwpNZ0Vu0C5Q4xSQC+u1t g18qOJswBz/38yhkgoC6NOYTycWKjYT9+11vOq15BHHlISuq970oi7W4X3xuAfZldikevC1tOs0Bh B4lMnEBsQnx3IMx0UzhVcMlMnacF0JUWtGfVPaqYH40L4SpkXsXR2MY6hg5PidRJqkizqPXON2DyG mCppZU+lw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gtC09-0001XH-J4; Mon, 11 Feb 2019 13:52:01 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 3C2032370CE11; Mon, 11 Feb 2019 14:51:59 +0100 (CET) Date: Mon, 11 Feb 2019 14:51:59 +0100 From: Peter Zijlstra To: Ingo Molnar Cc: Julien Thierry , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, mingo@redhat.com, catalin.marinas@arm.com, will.deacon@arm.com, james.morse@arm.com, hpa@zytor.com, valentin.schneider@arm.com Subject: Re: [PATCH v3 3/4] uaccess: Check no rescheduling function is called in unsafe region Message-ID: <20190211135159.GC32511@hirez.programming.kicks-ass.net> References: <1547560709-56207-1-git-send-email-julien.thierry@arm.com> <1547560709-56207-4-git-send-email-julien.thierry@arm.com> <20190211134527.GA121589@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190211134527.GA121589@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 11, 2019 at 02:45:27PM +0100, Ingo Molnar wrote: > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index a674c7db..b1bb7e9 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -3289,6 +3289,14 @@ static inline void schedule_debug(struct task_struct *prev) > > __schedule_bug(prev); > > preempt_count_set(PREEMPT_DISABLED); > > } > > + > > + if (IS_ENABLED(CONFIG_DEBUG_UACCESS_SLEEP) && > > + unlikely(unsafe_user_region_active())) { > > + printk(KERN_ERR "BUG: scheduling while user_access enabled: %s/%d/0x%08x\n", > > + prev->comm, prev->pid, preempt_count()); > > + dump_stack(); > > + } > > + > > rcu_sleep_check(); > > > > profile_hit(SCHED_PROFILING, __builtin_return_address(0)); > > @@ -6151,6 +6159,20 @@ void ___might_sleep(const char *file, int line, int preempt_offset) > > EXPORT_SYMBOL(___might_sleep); > > #endif > > > > +#ifdef CONFIG_DEBUG_UACCESS_SLEEP > > +void __might_resched(const char *file, int line) > > +{ > > + if (!unsafe_user_region_active()) > > + return; > > Could you please more clearly explain why you want/need an exception from > the __might_resched() debug warning? In specific; how is the addition in schedule_debug() not triggering on PREEMPT=y kernels? If code is preemptible, you can (get) schedule(d). If it is not preemptible; you do not need these additional tests.