Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752624AbbKQHnp (ORCPT ); Tue, 17 Nov 2015 02:43:45 -0500 Received: from mx2.suse.de ([195.135.220.15]:47297 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751339AbbKQHno (ORCPT ); Tue, 17 Nov 2015 02:43:44 -0500 Subject: Re: [PATCH V4] mm: fix kernel crash in khugepaged thread To: yalin wang , Steven Rostedt References: <1447316462-19645-1-git-send-email-yalin.wang2010@gmail.com> <20151112092923.19ee53dd@gandalf.local.home> <5645BFAA.1070004@suse.cz> <20151113090115.1ad4235b@gandalf.local.home> <2F74FF6B-66DC-4BF9-972A-C2F5FFFA979F@gmail.com> <5649ACF6.1000704@suse.cz> <20151116092501.761f31d7@gandalf.local.home> <233209B0-A466-4149-93C6-7173FF0FD4C5@gmail.com> <20151116214304.6fa42a4e@grimm.local.home> <8582F660-B54A-474B-960E-CD5D0FF6428F@gmail.com> Cc: Ingo Molnar , Andrew Morton , Ebru Akagunduz , Rik van Riel , "Kirill A. Shutemov" , jmarchan@redhat.com, mgorman@techsingularity.net, willy@linux.intel.com, linux-kernel , linux-mm@kvack.org From: Vlastimil Babka Message-ID: <564ADAB1.9030500@suse.cz> Date: Tue, 17 Nov 2015 08:43:45 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <8582F660-B54A-474B-960E-CD5D0FF6428F@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1842 Lines: 63 On 17.11.2015 4:58, yalin wang wrote: > >> On Nov 17, 2015, at 10:43, Steven Rostedt wrote: >> >> On Tue, 17 Nov 2015 10:21:47 +0800 >> yalin wang wrote: >> >> >> >> Because the print_fmt has nothing to do with the fields. You can have >> as your print_fmt as: >> >> TP_printk("Message = %s", "hello dolly!") >> >> And both userspace and the kernel with process that correctly (if I got >> string processing working in userspace, which I believe I do). The >> string is processed, it's not dependent on TP_STRUCT__entry() unless it >> references a field there. Which can also be used too: >> >> TP_printk("Message = %s", __entry->musical ? "Hello dolly!" : >> "Death Trap!") >> >> userspace will see in the entry: >> >> print_fmt: "Message = %s", REC->musical ? "Hello dolly!" : "Death Trap!" >> >> as long as the field "musical" exists, all is well. >> >> -- Steve > Aha, i see. > Thanks very much for your explanation. > Better print fat is : > TP_printk("mm=%p, scan_pfn=%s, writable=%d, referenced=%d, none_or_zero=%d, status=%s, unmapped=%d", > __entry->mm, > __entry->pfn == (-1UL) ? "(null)" : itoa(buff, __entry->pin, 10), …..) > > is this possible ? I doubt so. Why don't we just do (with %lx): __entry->pfn != -1UL ? __entry->pfn : 0, Status already tells us that it's not a real pfn 0 (which I doubt would be userspace-mapped and thus reachable by khugepaged anyway?). Also it's what some other tracepoints do, see e.g. mm_page class in include/trace/events/kmem.h. > Thanks > > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/