drm/fb-helper: Don't call dirty callback for untouched clips

tiwai · danvet · commit 87d3b6588f9b · 2016-10-26T10:31:53.000+02:00
Since 4.7 kernel, we've seen the error messages like kernel: [TTM] Buffer eviction failed kernel: qxl 0000:00:02.0: object_init failed for (4026540032, 0x00000001) kernel: [drm:qxl_alloc_bo_reserved [qxl]] *ERROR* failed to allocate VRAM BO on QXL when switching and accessing on VT. The culprit was the generic deferred_io code (qxl driver switched to it since 4.7). There is a race between the dirty clip update and the call of callback. In drm_fb_helper_dirty(), the dirty clip is updated in the spinlock, while it kicks off the update worker outside the spinlock. Meanwhile the update worker clears the dirty clip in the spinlock, too. Thus, when drm_fb_helper_dirty() is called concurrently, schedule_work() is called after the clip is cleared in the first worker call. This patch addresses it by validating the clip before calling the dirty fb callback. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98322 Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1003298 Fixes: eaa434d ('drm/fb-helper: Add fb_deferred_io support') Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/20161020150530.5787-1-tiwai@suse.de
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
@@ -644,7 +644,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
 	clip->x2 = clip->y2 = 0;
 	spin_unlock_irqrestore(&helper->dirty_lock, flags);
 
-	helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
+	/* call dirty callback only when it has been really touched */
+	if (clip_copy.x1 < clip_copy.x2 && clip_copy.y1 < clip_copy.y2)
+		helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
 }
 
 /**

Original file line number	Diff line number	Diff line change
`@@ -644,7 +644,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)`
`644`	`644`	`clip->x2 = clip->y2 = 0;`
`645`	`645`	`spin_unlock_irqrestore(&helper->dirty_lock, flags);`
`646`	`646`
`647`		`- helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);`
	`647`	`+ /* call dirty callback only when it has been really touched */`
	`648`	`+ if (clip_copy.x1 < clip_copy.x2 && clip_copy.y1 < clip_copy.y2)`
	`649`	`+ helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);`
`648`	`650`	`}`
`649`	`651`
`650`	`652`	`/**`