From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vineet Gupta Subject: Re: n_tty_write() going into schedule but NOT coming out Date: Sat, 6 Apr 2013 15:02:02 +0530 Message-ID: <515FEB92.9060707@synopsys.com> References: <5156DC21.20901@synopsys.com> <5159925B.5050806@synopsys.com> <1364829008.3617.21.camel@thor.lan> <515ADC96.7090908@synopsys.com> <1365191567.3585.10.camel@thor.lan> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from us02smtp2.synopsys.com ([198.182.60.77]:48110 "EHLO alvesta.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1163221Ab3DFJcQ (ORCPT ); Sat, 6 Apr 2013 05:32:16 -0400 In-Reply-To: <1365191567.3585.10.camel@thor.lan> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Peter Hurley Cc: lkml , linux-serial@vger.kernel.org, Jiri Slaby On 04/06/2013 01:22 AM, Peter Hurley wrote: > I'll see if I can reproduce this over the weekend on an old single-core laptop I > still have. TIA for doing this. > There were some race conditions in the N_TTY line discipline which I > recently fixed. Those changes are in linux-next. Can you test if this is > reproducible on linux-next? I tried today's -next and I see the same issue :-( > Assuming I don't reproduce this on the laptop, the only other > explanation I can think of right now is that ARCLinux is not properly > handling signal-driven i/o (assuming the BusyBox /bin/sh uses SIGIO). Do > you know if there is anything special about the way ARCLinux handle > signals? No, it's pretty standard stuff - we are uClibc based though - as opposed to glibc so there might be some subtleties - but we do run LTP open posix regularly. Also the test setup is a slowish 80MHz FPGA so this is not something many people have in their regular test setups. I'll start reading the relevant code myself - and will be willing to take any debug/test patches which help with troubleshooting of this issue. Just to re-iterate, my test setup has a minimal busybox based rootfs, 3 telnet sessions, each running a while true; do find / -name "*" ; done I'm running out of ramfs, no external disk/nfs mounts to reduce the peripheral I/O slowing down the find (although NFS stuff will be caches anyways after first fetch). Also please make sure you have CONFIG_PREEMPT_COUNT otherwise there's a possibility (atleast on ARC builds) that a stale register causes timer list to be corrupted in mod_timer(). Thx, -Vineet