Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758701Ab3DAN6Q (ORCPT ); Mon, 1 Apr 2013 09:58:16 -0400 Received: from alvesta.synopsys.com ([198.182.60.77]:56255 "EHLO alvesta.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758647Ab3DAN6E (ORCPT ); Mon, 1 Apr 2013 09:58:04 -0400 Message-ID: <5159925B.5050806@synopsys.com> Date: Mon, 1 Apr 2013 19:27:47 +0530 From: Vineet Gupta User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 Newsgroups: gmane.linux.serial,gmane.linux.kernel To: lkml CC: , Ingo Molnar , "Peter Zijlstra" , Jiri Slaby , Peter Hurley Subject: Re: n_tty_write() going into schedule but NOT coming out References: <5156DC21.20901@synopsys.com> In-Reply-To: <5156DC21.20901@synopsys.com> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.12.197.41] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1988 Lines: 60 Hi, Any thoughts: I observe the same issue even with CONFIG_PREEMPT and CONFIG_PREEMPT_COUNT -Vineet On 03/30/2013 06:05 PM, Vineet Gupta wrote: > Hi, > > I've been stress testing ARC Linux 3.8 (same happens for 3.9-rc3 as well). The > setup has 3 telnet sessions, each running find . -name "*" in a loop. > The platform is a FPGA @ 80 MHz, running a single core ARC700 so kernel .config > has !SMP and PREEMPT_NONE. > > After ~10 mins of run, I see that one of the telnet session gets stuck (and later > the 2nd one as well), while system is still alive, 3rd telnet is running find merrily. > > [ARCLinux]$ ps > .... > 7 root 0:00 inetd > 62 root 0:00 -/bin/sh > 64 root 1:34 telnetd -i -l /bin/sh > 65 root 0:00 /bin/sh > 75 root 1:47 telnetd -i -l /bin/sh > 76 root 0:00 /bin/sh > 79 root 0:53 telnetd -i -l /bin/sh > 80 root 0:00 /bin/sh > 281 root 0:00 find / -name * <--- stuck > 358 root 0:03 find / -name * <--- stuck > 377 root 0:00 find / -name * > 378 root 0:00 ps > > Hung find task is sitting in the schedule() call in n_tty_write() > > [ARCLinux]$ cat /proc/281/stack > [<8065945e>] n_tty_write+0x23a/0x424 > [<80655cd4>] tty_write+0x1ac/0x2d4 > [<805976ba>] vfs_write+0x92/0x110 > [<80597816>] sys_write+0x4e/0x88 > [<8050e780>] ret_from_system_call+0x0/0x4 > > This task never resumes out of schedule() - verified by putting a hardware > breakpoint on next insn - using a JTAG host debugger. > > Attached are .config, /proc/281/sched, /proc/schedstat, /proc/sched_debug > > My knowledge of schedular is close to none, hence any tips to debug this further > would be much appreciated. > > > TIA, > -Vineet > -- 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/