Hi Am 16.02.23 um 21:11 schrieb Daniel Vetter:
On Thu, Feb 16, 2023 at 03:06:20PM +0100, Thomas Zimmermann wrote:Move drm_fb_helper_unprepare() from drm_fb_helper_fini() into the calling fbdev implementation. Avoids a possible stale mutex with generic fbdev code. As indicated by its name, drm_fb_helper_prepare() prepares struct drm_fb_helper before setting up the fbdev support with a call to drm_fb_helper_init(). In legacy fbdev emulation, this happens next to each other. If successful, drm_fb_helper_fini() later tear down the fbdev device and also unprepare via drm_fb_helper_unprepare(). Generic fbdev emulation prepares struct drm_fb_helper immediately after allocating the instance. It only calls drm_fb_helper_init() as part of processing a hotplug event. If the hotplug-handling fails, it runs drm_fb_helper_fini(). This unprepares the fb-helper instance and the next hotplug event runs on stale data. Solve this by moving drm_fb_helper_unprepare() from drm_fb_helper_fini() into the fbdev implementations. Call it right before freeing the fb-helper instance. Fixes: 4825797c36da ("drm/fb-helper: Introduce drm_fb_helper_unprepare()") Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> Cc: Maxime Ripard <mripard@xxxxxxxxxx> Cc: David Airlie <airlied@xxxxxxxxx> Cc: Daniel Vetter <daniel@xxxxxxxx> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>This reminds me of an old patch I just recently stumbled over again: https://lore.kernel.org/dri-devel/Y3St2VHJ7jEmcNFw@phenom.ffwll.local/ Should I resurrect that one maybe and send it out? I think that also ties a bit into your story here.
I don't think it will be necessary. I began to convert the existing fbdev emulation to make use of drm_client, which should resove a number of problems. I expect to post this after the various trees have merged the recent changes to fbdev helpers.
Best regards Thomas
--- drivers/gpu/drm/armada/armada_fbdev.c | 3 +++ drivers/gpu/drm/drm_fb_helper.c | 2 -- drivers/gpu/drm/drm_fbdev_generic.c | 2 ++ drivers/gpu/drm/exynos/exynos_drm_fbdev.c | 3 ++- drivers/gpu/drm/gma500/framebuffer.c | 2 ++ drivers/gpu/drm/i915/display/intel_fbdev.c | 1 + drivers/gpu/drm/msm/msm_fbdev.c | 2 ++ drivers/gpu/drm/omapdrm/omap_fbdev.c | 2 ++ drivers/gpu/drm/radeon/radeon_fb.c | 2 ++ drivers/gpu/drm/tegra/fb.c | 1 + 10 files changed, 17 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/armada/armada_fbdev.c b/drivers/gpu/drm/armada/armada_fbdev.c index 07e410c62b7a..0e44f53e9fa4 100644 --- a/drivers/gpu/drm/armada/armada_fbdev.c +++ b/drivers/gpu/drm/armada/armada_fbdev.c @@ -147,6 +147,7 @@ int armada_fbdev_init(struct drm_device *dev) err_fb_setup: drm_fb_helper_fini(fbh); err_fb_helper: + drm_fb_helper_unprepare(fbh); priv->fbdev = NULL; return ret; } @@ -164,6 +165,8 @@ void armada_fbdev_fini(struct drm_device *dev) if (fbh->fb) fbh->fb->funcs->destroy(fbh->fb);+ drm_fb_helper_unprepare(fbh);+ priv->fbdev = NULL; } } diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 28c428e9c530..a39998047f8a 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -590,8 +590,6 @@ void drm_fb_helper_fini(struct drm_fb_helper *fb_helper)I think it would be good to update the kerneldoc of _init() and _fini() here to mention each another like we usually do with these pairs. Same with prepare/unprepare() although the latter rerfences _prepare() already.} mutex_unlock(&kernel_fb_helper_lock);- drm_fb_helper_unprepare(fb_helper);- if (!fb_helper->client.funcs) drm_client_release(&fb_helper->client); } diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c index 365f80717fa1..4d6325e91565 100644 --- a/drivers/gpu/drm/drm_fbdev_generic.c +++ b/drivers/gpu/drm/drm_fbdev_generic.c @@ -65,6 +65,8 @@ static void drm_fbdev_fb_destroy(struct fb_info *info)drm_client_framebuffer_delete(fb_helper->buffer);drm_client_release(&fb_helper->client); + + drm_fb_helper_unprepare(fb_helper); kfree(fb_helper); }diff --git a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c b/drivers/gpu/drm/exynos/exynos_drm_fbdev.cindex b89e33af8da8..4929ffe5a09a 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c +++ b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c @@ -183,8 +183,8 @@ int exynos_drm_fbdev_init(struct drm_device *dev)err_setup:drm_fb_helper_fini(helper); - err_init: + drm_fb_helper_unprepare(helper); private->fb_helper = NULL; kfree(fbdev);@@ -219,6 +219,7 @@ void exynos_drm_fbdev_fini(struct drm_device *dev)fbdev = to_exynos_fbdev(private->fb_helper);exynos_drm_fbdev_destroy(dev, private->fb_helper);+ drm_fb_helper_unprepare(private->fb_helper); kfree(fbdev); private->fb_helper = NULL; } diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c index 1f04c07ee180..f471e0cb7298 100644 --- a/drivers/gpu/drm/gma500/framebuffer.c +++ b/drivers/gpu/drm/gma500/framebuffer.c @@ -427,6 +427,7 @@ int psb_fbdev_init(struct drm_device *dev) fini: drm_fb_helper_fini(fb_helper); free: + drm_fb_helper_unprepare(fb_helper); kfree(fb_helper); return ret; } @@ -439,6 +440,7 @@ static void psb_fbdev_fini(struct drm_device *dev) return;psb_fbdev_destroy(dev, dev_priv->fb_helper);+ drm_fb_helper_unprepare(dev_priv->fb_helper); kfree(dev_priv->fb_helper); dev_priv->fb_helper = NULL; } diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c index 6113d7627d45..98029059f701 100644 --- a/drivers/gpu/drm/i915/display/intel_fbdev.c +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c @@ -352,6 +352,7 @@ static void intel_fbdev_destroy(struct intel_fbdev *ifbdev) if (ifbdev->fb) drm_framebuffer_remove(&ifbdev->fb->base);+ drm_fb_helper_unprepare(&ifbdev->helper);kfree(ifbdev); }diff --git a/drivers/gpu/drm/msm/msm_fbdev.c b/drivers/gpu/drm/msm/msm_fbdev.cindex 915b213f3a5c..c804e5ba682a 100644 --- a/drivers/gpu/drm/msm/msm_fbdev.c +++ b/drivers/gpu/drm/msm/msm_fbdev.c @@ -170,6 +170,7 @@ struct drm_fb_helper *msm_fbdev_init(struct drm_device *dev) fini: drm_fb_helper_fini(helper); fail: + drm_fb_helper_unprepare(helper); kfree(fbdev); return NULL; } @@ -196,6 +197,7 @@ void msm_fbdev_free(struct drm_device *dev) drm_framebuffer_remove(fbdev->fb); }+ drm_fb_helper_unprepare(helper);kfree(fbdev);priv->fbdev = NULL;diff --git a/drivers/gpu/drm/omapdrm/omap_fbdev.c b/drivers/gpu/drm/omapdrm/omap_fbdev.c index fc5f52d567c6..84429728347f 100644 --- a/drivers/gpu/drm/omapdrm/omap_fbdev.c +++ b/drivers/gpu/drm/omapdrm/omap_fbdev.c @@ -256,6 +256,7 @@ void omap_fbdev_init(struct drm_device *dev) fini: drm_fb_helper_fini(helper); fail: + drm_fb_helper_unprepare(helper); kfree(fbdev);dev_warn(dev->dev, "omap_fbdev_init failed\n");@@ -286,6 +287,7 @@ void omap_fbdev_fini(struct drm_device *dev) if (fbdev->fb) drm_framebuffer_remove(fbdev->fb);+ drm_fb_helper_unprepare(helper);kfree(fbdev);priv->fbdev = NULL;diff --git a/drivers/gpu/drm/radeon/radeon_fb.c b/drivers/gpu/drm/radeon/radeon_fb.c index 6e5eed0e157c..c4807f0c43bc 100644 --- a/drivers/gpu/drm/radeon/radeon_fb.c +++ b/drivers/gpu/drm/radeon/radeon_fb.c @@ -367,6 +367,7 @@ int radeon_fbdev_init(struct radeon_device *rdev) fini: drm_fb_helper_fini(&rfbdev->helper); free: + drm_fb_helper_unprepare(&rfbdev->helper); kfree(rfbdev); return ret; } @@ -377,6 +378,7 @@ void radeon_fbdev_fini(struct radeon_device *rdev) return;radeon_fbdev_destroy(rdev->ddev, rdev->mode_info.rfbdev);+ drm_fb_helper_unprepare(&rdev->mode_info.rfbdev->helper); kfree(rdev->mode_info.rfbdev); rdev->mode_info.rfbdev = NULL; } diff --git a/drivers/gpu/drm/tegra/fb.c b/drivers/gpu/drm/tegra/fb.c index 153c39c32c71..bfebe2786d61 100644 --- a/drivers/gpu/drm/tegra/fb.c +++ b/drivers/gpu/drm/tegra/fb.c @@ -315,6 +315,7 @@ static struct tegra_fbdev *tegra_fbdev_create(struct drm_device *drm)static void tegra_fbdev_free(struct tegra_fbdev *fbdev){ + drm_fb_helper_unprepare(&fbdev->base);Ok this one tegra change was a bit tricky, drivers really should just use drmm_/devm_ for everything :-) With the kerneldoc augmented: Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>kfree(fbdev); }--2.39.1
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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