From a7442b93cf32c1e1ddb721a26cd1f92302e2a222 Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Wed, 9 Mar 2016 12:52:53 +0100 Subject: [PATCH] drm/i915: Fix races on fbdev MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Reported-by: "Li, Weinan Z" Cc: Chris Wilson Cc: stable@vger.kernel.org Signed-off-by: Lukas Wunner Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/20160309115147.67B2B6E0D3@gabe.freedesktop.org --- drivers/gpu/drm/i915/i915_dma.c | 8 +++----- drivers/gpu/drm/i915/intel_fbdev.c | 3 +++ 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c index fc8ac98c12d7..1ac1ea969eec 100644 --- a/drivers/gpu/drm/i915/i915_dma.c +++ b/drivers/gpu/drm/i915/i915_dma.c @@ -493,11 +493,9 @@ static int i915_load_modeset_init(struct drm_device *dev) * 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); diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c index 5e0dcb3961be..153ea7a3fcf6 100644 --- a/drivers/gpu/drm/i915/intel_fbdev.c +++ b/drivers/gpu/drm/i915/intel_fbdev.c @@ -808,6 +808,8 @@ void intel_fbdev_set_suspend(struct drm_device *dev, int state, bool synchronous 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); } @@ -819,6 +821,7 @@ void intel_fbdev_restore_mode(struct drm_device *dev) struct intel_fbdev *ifbdev = dev_priv->fbdev; struct drm_fb_helper *fb_helper; + async_synchronize_full(); if (!ifbdev) return; -- 2.20.1