lkml.org 
[lkml]   [2008]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: TIOCGWINSZ retuns old pty size after receiving SIGWINCH


* On 2008-08-19 Ico Doornekamp <lkml@zevv.nl> wrote :

>
>
> * On 2008-08-19 Andrew Morton <akpm@linux-foundation.org> wrote :
>
> > On Tue, 19 Aug 2008 09:54:14 +0200 Ico Doornekamp <lkml@zevv.nl> wrote:
> > >
> > > * On 2008-08-19 Andrew Morton <akpm@linux-foundation.org> wrote :
> > >
> > > > On Sun, 10 Aug 2008 17:08:59 +0200 Ico Doornekamp <lkml@zevv.nl> wrote:
> > > >
> > > > > Recently my X terminals showed annoying behaviour where the application
> > > > > in the terminal was not resized properly to the actual size of the X
> > > > > terminal emulator window, resulting in a lot of misaligned text on the
> > > > > screen. Hunting the issue down from the windowmanager and the terminal
> > > > > emulator program, I suspect the problem might lie in the kernel. I'm
> > > > > running 2.6.26 on a dual core i386.
> > > > >
> > > > > What I see is this: the userspace application receives a SIGWINCH signal
> > > > > and acquires the terminal size usign the TIOCGWINSZ ioctl. It seems that
> > > > > in some cases the old instead of the new terminal size is returned.
> > > > > A small delay before the ioctl seems to 'fix' this behaviour.
> > > > >
> > > > > I noticed some changes involving locking in the the pty code in the last
> > > > > kernel verions, could one of these changes cause the above behaviour ? If
> > > > > so, wouldn't this affect much more users ?
> > > >
> > > > hm, that code is pretty simple and although it does the SIGWINCH and
> > > > the window-size setting in a peculiar order, it looks to be race-free.
> > > >
> > > > Approximately what proportion of the time does it go wrong?
> > >
> > > I guess about 10 to 20% of the resizes. I happen to be using a tiling
> > > window manager which causes resizing more often and more agressive then
> > > 'normal' window managers, I guess this helps triggering the problem.
> > >
> > > I temporary worked around this issue this by changing the order of the
> > > signal and the updating of the pty size in tty_io.c's tiocswinsz(), but
> > > this is not much of a real fix.
> > >
> >
> > Well damn. Are you sure? The code looks solid to me.
> >
> > At least, it does after
> >
> > Author: Alan Cox <alan@redhat.com> 2008-08-15 02:39:38
> > Committer: Linus Torvalds <torvalds@linux-foundation.org> 2008-08-15 10:34:07
> > Parent: 000b9151d7851cc1e490b2a76d0206e524f43cca (Fix race/oops in tty layer after BKL pushdown)
> > Branches: git-cifs, git-ia64, git-nfs, git-powerpc-merge, linux-next, remotes/origin/master
> > Follows: v2.6.27-rc3
> > Precedes: next-20080818
> >
> > tty: remove resize window special case
> >
> > perhaps you're still running a kernel which is earlier than that?
>
> I reported the behaviour on 2.6.26.2, but I was not aware this issue was
> adressed already in the 2.6.27 tree. I will update to the latest 2.6.27
> rc and report if the problem still persists.

I am not able to reproduce the problem with git 2.6.27-rc3-next-20080819.



\
 
 \ /
  Last update: 2008-08-19 19:59    [W:0.045 / U:4.512 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site