From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 12 Jan 2012 14:00:17 -0800 From: Greg KH To: Jiri Slaby Cc: Arnd Bergmann , alan@linux.intel.com, linux-serial@vger.kernel.org, jirislaby@gmail.com, linux-kernel@vger.kernel.org, "3.0 3.1 3.2" Subject: Re: [PATCH] TTY: fix UV serial console regression Message-ID: <20120112220017.GA1440@suse.de> References: <4EDE988B.6010501@suse.cz> <1326405315-6601-1-git-send-email-jslaby@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1326405315-6601-1-git-send-email-jslaby@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: On Thu, Jan 12, 2012 at 10:55:15PM +0100, Jiri Slaby wrote: > Commit 74c2107759d (serial: Use block_til_ready helper) and its fixup > 3f582b8c110 (serial: fix termios settings in open) introduced a > regression on UV systems. The serial eventually freezes while being > used. It's completely unpredictable and sometimes needs a heap of > traffic to happen first. > > To reproduce this, yast installation was used as it turned out to be > pretty reliable in reproducing. Especially during installation process > where one doesn't have an SSH daemon running. And no monitor as the HW > is completely headless. So this was fun to find. Given the machine > doesn't boot on vanilla before 2.6.36 final. (And the commits above > are older.) > > Unless there is some bad race in the code, the hardware seems to be > pretty broken. Otherwise pure MSR read should not cause such a bug, > or? > > So to prevent the bug, revert to the old behavior. I.e. read modem > status only if we really have to -- for non-CLOCAL set serials. > Non-CLOCAL works on this hardware OK, I tried. See? I don't. > > And document that shit. Thanks for tracking this down, I'll queue it up and get it to Linus after 3.3-rc1 is out. greg k-h