Re: 4.9-rc1 lockdep warning suggesting a deadlock between nouveau and i915 with prime video outputs active

From: Chris Wilson <chris@chris-wilson.co.uk>
To: Hans de Goede <hdegoede@redhat.com>
Cc: Ben Skeggs <bskeggs@redhat.com>, dri-devel@lists.freedesktop.org
Subject: Re: 4.9-rc1 lockdep warning suggesting a deadlock between nouveau and i915 with prime video outputs active
Date: Wed, 9 Nov 2016 17:26:00 +0000	[thread overview]
Message-ID: <20161109172600.GB9300@nuc-i3427.alporthouse.com> (raw)
In-Reply-To: <36638da4-8cf3-6fb6-26a0-8e9c4a0e2e05@redhat.com>

On Wed, Nov 09, 2016 at 06:02:40PM +0100, Hans de Goede wrote:
> Hi,
> 
> I noticed this while testing the displayport output attached
> to the nvidia GPU on a Thinkpad P50 while the intel GPU
> was driving the LCD panel (and was the primary GPU according
> to Xorg). This was while logging into gnome-3 with Xorg-1.19-rc2,
> from gdm (also running on top of Xorg-1.19-rc2).

Worth trying

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 6efdba4993fc..3e4dc782812d 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -505,7 +505,9 @@ int drm_dev_init(struct drm_device *dev,
 
        spin_lock_init(&dev->buf_lock);
        spin_lock_init(&dev->event_lock);
-       mutex_init(&dev->struct_mutex);
+       __mutex_init(&dev->struct_mutex,
+                    "struct_mutex",
+                    &dev->struct_mutex_class);
        mutex_init(&dev->filelist_mutex);
        mutex_init(&dev->ctxlist_mutex);
        mutex_init(&dev->master_mutex);
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index ae49c3174d24..ed2e53534c2e 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -808,6 +808,7 @@ struct drm_device {
 
        /** \name Locks */
        /*@{ */
+       struct lock_class_key struct_mutex_class;
        struct mutex struct_mutex;      /**< For others */
        struct mutex master_mutex;      /**< For drm_minor::master and drm_file::is_master */
        /*@} */

to test for a false positive first.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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