Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752215AbbKQD6x (ORCPT ); Mon, 16 Nov 2015 22:58:53 -0500 Received: from mail-pa0-f54.google.com ([209.85.220.54]:36333 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751421AbbKQD6w convert rfc822-to-8bit (ORCPT ); Mon, 16 Nov 2015 22:58:52 -0500 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.0 \(3094\)) Subject: Re: [PATCH V4] mm: fix kernel crash in khugepaged thread From: yalin wang In-Reply-To: <20151116214304.6fa42a4e@grimm.local.home> Date: Tue, 17 Nov 2015 11:58:44 +0800 Cc: Vlastimil Babka , 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 Content-Transfer-Encoding: 8BIT Message-Id: <8582F660-B54A-474B-960E-CD5D0FF6428F@gmail.com> 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> To: Steven Rostedt X-Mailer: Apple Mail (2.3094) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1716 Lines: 57 > On Nov 17, 2015, at 10:43, Steven Rostedt wrote: > > On Tue, 17 Nov 2015 10:21:47 +0800 > yalin wang wrote: > > >> i have not tried , >> just a question, >> if you print a %s , but don’t call trace_define_field() do define this string in >> __entry , how does user space perf tool to get this string info and print it ? >> i am curious .. >> i can try this when i have time. and report to you . > > 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 ? 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/