[PATCH] xfree86: detach scanout pixmaps when detaching output GPUs

[Aaron Plattner]

Commit 8f4640bdb9d3988148e09a08d2c7e3bab1d538d6 fixed a bit of a
chicken-and-egg problem by detaching GPU screens when their providers
are destroyed, which happens before CloseScreen is called.  However,
this created a new problem: the GPU screen tears down its RandR crtc
objects during CloseScreen and if one of them is active, it tries to
detach the scanout pixmap then.  This crashes because
RRCrtcDetachScanoutPixmap tries to get the master screen's screen
pixmap, but crtc->pScreen->current_master is already NULL at that
point.

It doesn't make sense for an unbound GPU screen to still be scanning
out its former master screen's pixmap, so detach them first when the
provider is destroyed.

Signed-off-by: Aaron Plattner <aplattner at nvidia.com>
---
Dave, does this seem like a reasonable way to work around this particular crash?

 hw/xfree86/modes/xf86RandR12.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/hw/xfree86/modes/xf86RandR12.c b/hw/xfree86/modes/xf86RandR12.c
index 2817aaa..76614de 100644
--- a/hw/xfree86/modes/xf86RandR12.c
+++ b/hw/xfree86/modes/xf86RandR12.c
@@ -1771,6 +1771,19 @@ xf86RandR12EnterVT(ScrnInfoPtr pScrn)
     return RRGetInfo(pScreen, TRUE);    /* force a re-probe of outputs and notify clients about changes */
 }
 
+static void
+xf86DetachOutputGPU(ScreenPtr pScreen)
+{
+    rrScrPrivPtr rp = rrGetScrPriv(pScreen);
+    int i;
+
+    /* make sure there are no attached shared scanout pixmaps first */
+    for (i = 0; i < rp->numCrtcs; i++)
+        RRCrtcDetachScanoutPixmap(rp->crtcs[i]);
+
+    DetachOutputGPU(pScreen);
+}
+
 static Bool
 xf86RandR14ProviderSetOutputSource(ScreenPtr pScreen,
                                    RRProviderPtr provider,
@@ -1780,7 +1793,7 @@ xf86RandR14ProviderSetOutputSource(ScreenPtr pScreen,
         if (provider->output_source) {
             ScreenPtr cmScreen = pScreen->current_master;
 
-            DetachOutputGPU(pScreen);
+            xf86DetachOutputGPU(pScreen);
             AttachUnboundGPU(cmScreen, pScreen);
         }
         provider->output_source = NULL;
@@ -1808,7 +1821,7 @@ xf86RandR14ProviderSetOffloadSink(ScreenPtr pScreen,
     if (!sink_provider) {
         if (provider->offload_sink) {
             ScreenPtr cmScreen = pScreen->current_master;
-            DetachOutputGPU(pScreen);
+            xf86DetachOutputGPU(pScreen);
             AttachUnboundGPU(cmScreen, pScreen);
         }
 
@@ -1899,7 +1912,7 @@ xf86RandR14ProviderDestroy(ScreenPtr screen, RRProviderPtr provider)
             RRSetChanged(screen);
         }
         else if (config->randr_provider->output_source) {
-            DetachOutputGPU(screen);
+            xf86DetachOutputGPU(screen);
             config->randr_provider->output_source = NULL;
             RRSetChanged(screen);
         }
-- 
1.8.2.2