From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 26 Sep 2013 21:10:34 +0200 From: Oleg Nesterov To: Peter Hurley Cc: Greg Kroah-Hartman , Jiri Slaby , Andrew Morton , Linus Torvalds , codonell , Eduard Benes , Karel Srot , Matt Newsome , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] tty: Fix SIGTTOU not sent with tcflush() Message-ID: <20130926191034.GA26591@redhat.com> References: <52437AA2.5040907@hurleysoftware.com> <1380154395-4232-1-git-send-email-peter@hurleysoftware.com> <20130926163633.GA22849@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130926163633.GA22849@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: On 09/26, Oleg Nesterov wrote: > > Thanks Peter. > > Well. I'am afraid my testing was wrong, because Karel reports > it fixes the problem... > > But. I applied this patch to my 3.11 tree (last commit is bff157b3a) > which also has the additional patch (03e12617 "tty: disassociate_ctty() > sends the extra SIGCONT"), and > > TET_CONFIG=CFG TET_ROOT=. ./T.tcflush 4 > > still fails... T.tcflush was compiled on another (Karel's) machine, > perhaps there is something in libc, I do not know. > > So let me ask just in case, I assume the fix below doesn't depend on > other changes I could miss? > > I'll retest after git-pull and report... Still fails under the Linus's tree + this patch. However!!! Tested-by: Oleg Nesterov It turns out, T.tcflush doesn't expect it can start as a process group leader. In this case setsid() fails, then tty_open() doesn't set signal->tty, and thus this patch makes no difference: tty_check_change() fails because tty doesn't match signal->tty. And indeed, this test passes if you run it under strace, or simply do $ TET_CONFIG=CFG TET_ROOT=. perl -e "system './T.tcflush 4'" And damn, the fact it doesn't fail under strace doesn't allow you to see that setsid() fails ;) This is probably explains why Karel reported success, perhaps he didn't run this test individually. Thanks again Peter. Perhaps my analysis was wrong (and I do not see setsid() in the sources), I do not really care. but perhaps tcflush.c should be updated. Oleg.