This is a note to let you know that I've just added the patch titled
drm/i915: Fix races on fbdev
to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-i915-fix-races-on-fbdev.patch
and it can be found in the queue-4.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a7442b93cf32c1e1ddb721a26cd1f92302e2a222 Mon Sep 17 00:00:00 2001
From: Lukas Wunner <lukas@xxxxxxxxx>
Date: Wed, 9 Mar 2016 12:52:53 +0100
Subject: drm/i915: Fix races on fbdev
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
From: Lukas Wunner <lukas@xxxxxxxxx>
commit a7442b93cf32c1e1ddb721a26cd1f92302e2a222 upstream.
The ->lastclose callback invokes intel_fbdev_restore_mode() and has
been witnessed to run before intel_fbdev_initial_config_async()
has finished.
We might likewise receive hotplug events before we've had a chance to
fully set up the fbdev.
Fix by waiting for the asynchronous thread to finish.
v2:
An async_synchronize_full() was also added to intel_fbdev_set_suspend()
in v1 which turned out to be entirely gratuitous. It caused a deadlock
on suspend (discovered by CI, thanks to Damien Lespiau and Tomi Sarvela
for CI support) and was unnecessary since a device is never suspended
until its ->probe callback (and all asynchronous tasks it scheduled)
have finished. See dpm_prepare(), which calls wait_for_device_probe(),
which calls async_synchronize_full().
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93580
Reported-by: Gustav Fägerlind <gustav.fagerlind@xxxxxxxxx>
Reported-by: "Li, Weinan Z" <weinan.z.li@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Link: http://patchwork.freedesktop.org/patch/msgid/20160309115147.67B2B6E0D3@xxxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_dma.c | 8 +++-----
drivers/gpu/drm/i915/intel_fbdev.c | 3 +++
2 files changed, 6 insertions(+), 5 deletions(-)
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -437,11 +437,9 @@ static int i915_load_modeset_init(struct
* Some ports require correctly set-up hpd registers for detection to
* work properly (leading to ghost connected connector status), e.g. VGA
* on gm45. Hence we can only set up the initial fbdev config after hpd
- * irqs are fully enabled. Now we should scan for the initial config
- * only once hotplug handling is enabled, but due to screwed-up locking
- * around kms/fbdev init we can't protect the fdbev initial config
- * scanning against hotplug events. Hence do this first and ignore the
- * tiny window where we will loose hotplug notifactions.
+ * irqs are fully enabled. We protect the fbdev initial config scanning
+ * against hotplug events by waiting in intel_fbdev_output_poll_changed
+ * until the asynchronous thread has finished.
*/
intel_fbdev_initial_config_async(dev);
--- a/drivers/gpu/drm/i915/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/intel_fbdev.c
@@ -797,6 +797,8 @@ void intel_fbdev_set_suspend(struct drm_
void intel_fbdev_output_poll_changed(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
+
+ async_synchronize_full();
if (dev_priv->fbdev)
drm_fb_helper_hotplug_event(&dev_priv->fbdev->helper);
}
@@ -808,6 +810,7 @@ void intel_fbdev_restore_mode(struct drm
struct intel_fbdev *ifbdev = dev_priv->fbdev;
struct drm_fb_helper *fb_helper;
+ async_synchronize_full();
if (!ifbdev)
return;
Patches currently in stable-queue which might be from lukas@xxxxxxxxx are
queue-4.5/drm-i915-fix-races-on-fbdev.patch
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