From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Galbraith Subject: Re: [ANNOUNCE] 3.18.7-rt2 Date: Tue, 24 Feb 2015 18:50:14 +0100 Message-ID: <1424800214.6955.30.camel@gmail.com> References: <20150223090617.GA26453@linutronix.de> <1424785301.8767.11.camel@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Sebastian Andrzej Siewior , linux-rt-users , LKML , Thomas Gleixner , rostedt@goodmis.org, John Kacur To: Gustavo Bittencourt Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On Tue, 2015-02-24 at 13:19 -0300, Gustavo Bittencourt wrote: > On Tue, Feb 24, 2015 at 10:41 AM, Mike Galbraith > wrote: > > locking, ww_mutex: fix ww_mutex vs self-deadlock > > > > If the caller already holds the mutex, task_blocks_on_rt_mutex() > > returns -EDEADLK, we proceed directly to rt_mutex_handle_deadlock() > > where it's instant game over. > > > > Let ww_mutexes return EDEADLK/EALREADY as they want to instead. > > > > Signed-off-by: Mike Galbraith > > --- > > kernel/locking/rtmutex.c | 17 +++++++++++------ > > 1 file changed, 11 insertions(+), 6 deletions(-) > > > > --- a/kernel/locking/rtmutex.c > > +++ b/kernel/locking/rtmutex.c > > The deadlock returned after I applied this patch in v3.18.7-rt2. Here is my log: Hrmph. I definitely want your patch to die ;-) It adds a whole new dimension to ww_mutex that only now exists in -rt. That's not good. My patchlet may not be perfect either, but it lets ww_mutex do that return EALREADY business it's supposed to, vs going straight to while(1). We can't have it both ways, so I suppose I'll fire up my old Q6600 box (that doesn't have annoying GTX980 that my userspace can't deal with DRM wise), and see if I can chase the nouveau thing down. I'm not all that enthusiastic though, as there are or at least were other issues with nouveau. Sebastian reported some completely _missing_ locking IIRC, that led to his box exploding. -Mike