linux-kernel - Re: [PATCH] drm: add locked variant of drm_fb_helper_force_kernel

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Message-ID: <20100412090506.26cf7179@virtuousgeek.org>
Date:	Mon, 12 Apr 2010 09:05:06 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Dave Airlie <airlied@...il.com>
Cc:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	James Simmons <jsimmons@...radead.org>
Subject: Re: [PATCH] drm: add locked variant of
 drm_fb_helper_force_kernel_mode

On Mon, 12 Apr 2010 10:05:00 +1000
Dave Airlie <airlied@...il.com> wrote:

> On Sat, Apr 10, 2010 at 8:11 AM, Jesse Barnes <jbarnes@...tuousgeek.org> wrote:
> > Needed for panic and kdb, since we need to avoid taking the mode_config
> > mutex.
> 
> One comment below.

Updated patch below.

-- 
Jesse Barnes, Intel Open Source Technology Center

>From 7e972aa6a2f432b8fd04cb5d1a51f4df2fddea62 Mon Sep 17 00:00:00 2001
From: Jesse Barnes <jbarnes@...tuousgeek.org>
Date: Thu, 8 Apr 2010 14:40:27 -0700
Subject: [PATCH] drm: add locked variant of drm_fb_helper_force_kernel_mode

Needed for panic and kdb, since we need to avoid taking the mode_config
mutex.

Signed-off-by: Jesse Barnes <jbarnes@...tuousgeek.org>
---
 drivers/gpu/drm/drm_fb_helper.c |   43 ++++++++++++++++++++++++++++++++------
 1 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 6929f5b..be0b95a 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -242,18 +242,22 @@ static int drm_fb_helper_parse_command_line(struct drm_fb_helper *fb_helper)
 	return 0;
 }
 
-bool drm_fb_helper_force_kernel_mode(void)
+bool drm_fb_helper_force_kernel_mode_locked(void)
 {
 	int i = 0;
 	bool ret, error = false;
 	struct drm_fb_helper *helper;
-
-	if (list_empty(&kernel_fb_helper_list))
-		return false;
+	struct drm_mode_set *mode_set;
+	struct drm_crtc *crtc;
 
 	list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) {
 		for (i = 0; i < helper->crtc_count; i++) {
-			struct drm_mode_set *mode_set = &helper->crtc_info[i].mode_set;
+			mode_set = &helper->crtc_info[i].mode_set;
+			crtc = helper->crtc_info[i].mode_set.crtc;
+
+			if (!crtc->enabled)
+				continue;
+
 			ret = drm_crtc_helper_set_config(mode_set);
 			if (ret)
 				error = true;
@@ -262,12 +266,37 @@ bool drm_fb_helper_force_kernel_mode(void)
 	return error;
 }
 
+bool drm_fb_helper_force_kernel_mode(void)
+{
+	bool ret;
+	struct drm_device *dev;
+	struct drm_fb_helper *helper;
+	struct drm_mode_set *mode_set;
+
+	if (list_empty(&kernel_fb_helper_list)) {
+		DRM_DEBUG_KMS("no fb helper list??\n");
+		return false;
+	}
+
+	/* Get the DRM device */
+	helper = list_first_entry(&kernel_fb_helper_list,
+				  struct drm_fb_helper,
+				  kernel_fb_list);
+	mode_set = &helper->crtc_info[0].mode_set;
+	dev = mode_set->crtc->dev;
+
+	mutex_lock(&dev->mode_config.mutex);
+	ret = drm_fb_helper_force_kernel_mode_locked();
+	mutex_unlock(&dev->mode_config.mutex);
+
+	return ret;
+}
+
 int drm_fb_helper_panic(struct notifier_block *n, unsigned long ununsed,
 			void *panic_str)
 {
 	DRM_ERROR("panic occurred, switching back to text console\n");
-	return drm_fb_helper_force_kernel_mode();
-	return 0;
+	return drm_fb_helper_force_kernel_mode_locked();
 }
 EXPORT_SYMBOL(drm_fb_helper_panic);
 
-- 
1.6.6.1


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