2019-10-25 20:44:00

by Will Deacon

[permalink] [raw]
Subject: Re: [PATCH] drm/radeon: Handle workqueue allocation failure

On Fri, Oct 25, 2019 at 06:06:26PM +0200, Michel D?nzer wrote:
> On 2019-10-25 1:04 p.m., Will Deacon wrote:
> > In the highly unlikely event that we fail to allocate the "radeon-crtc"
> > workqueue, we should bail cleanly rather than blindly march on with a
> > NULL pointer installed for the 'flip_queue' field of the 'radeon_crtc'
> > structure.
> >
> > This was reported previously by Nicolas, but I don't think his fix was
> > correct:
>
> Neither is this one I'm afraid. See my feedback on
> https://patchwork.freedesktop.org/patch/331534/ .

Thanks. Although I agree with you wrt the original patch, I don't think
the workqueue allocation failure is distinguishable from the CRTC allocation
failure with my patch. Are you saying that the error path there is broken
too?

Will


2019-10-25 20:46:09

by Michel Dänzer

[permalink] [raw]
Subject: Re: [PATCH] drm/radeon: Handle workqueue allocation failure

On 2019-10-25 6:18 p.m., Will Deacon wrote:
> On Fri, Oct 25, 2019 at 06:06:26PM +0200, Michel Dänzer wrote:
>> On 2019-10-25 1:04 p.m., Will Deacon wrote:
>>> In the highly unlikely event that we fail to allocate the "radeon-crtc"
>>> workqueue, we should bail cleanly rather than blindly march on with a
>>> NULL pointer installed for the 'flip_queue' field of the 'radeon_crtc'
>>> structure.
>>>
>>> This was reported previously by Nicolas, but I don't think his fix was
>>> correct:
>>
>> Neither is this one I'm afraid. See my feedback on
>> https://patchwork.freedesktop.org/patch/331534/ .
>
> Thanks. Although I agree with you wrt the original patch, I don't think
> the workqueue allocation failure is distinguishable from the CRTC allocation
> failure with my patch. Are you saying that the error path there is broken
> too?

The driver won't actually work if radeon_crtc_init bails silently, it'll
just fall over at some later point.


--
Earthling Michel Dänzer | https://redhat.com
Libre software enthusiast | Mesa and X developer

2019-10-31 16:57:00

by Will Deacon

[permalink] [raw]
Subject: Re: [PATCH] drm/radeon: Handle workqueue allocation failure

On Fri, Oct 25, 2019 at 06:20:01PM +0200, Michel D?nzer wrote:
> On 2019-10-25 6:18 p.m., Will Deacon wrote:
> > On Fri, Oct 25, 2019 at 06:06:26PM +0200, Michel D?nzer wrote:
> >> On 2019-10-25 1:04 p.m., Will Deacon wrote:
> >>> In the highly unlikely event that we fail to allocate the "radeon-crtc"
> >>> workqueue, we should bail cleanly rather than blindly march on with a
> >>> NULL pointer installed for the 'flip_queue' field of the 'radeon_crtc'
> >>> structure.
> >>>
> >>> This was reported previously by Nicolas, but I don't think his fix was
> >>> correct:
> >>
> >> Neither is this one I'm afraid. See my feedback on
> >> https://patchwork.freedesktop.org/patch/331534/ .
> >
> > Thanks. Although I agree with you wrt the original patch, I don't think
> > the workqueue allocation failure is distinguishable from the CRTC allocation
> > failure with my patch. Are you saying that the error path there is broken
> > too?
>
> The driver won't actually work if radeon_crtc_init bails silently, it'll
> just fall over at some later point.

Ok, so how about fleshing it out as per below?

Will

--->8

diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index e81b01f8db90..177acee06620 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -668,21 +668,29 @@ static const struct drm_crtc_funcs radeon_crtc_funcs = {
.page_flip_target = radeon_crtc_page_flip_target,
};

-static void radeon_crtc_init(struct drm_device *dev, int index)
+static int radeon_crtc_init(struct drm_device *dev, int index)
{
struct radeon_device *rdev = dev->dev_private;
struct radeon_crtc *radeon_crtc;
+ struct workqueue_struct *wq;
int i;

radeon_crtc = kzalloc(sizeof(struct radeon_crtc) + (RADEONFB_CONN_LIMIT * sizeof(struct drm_connector *)), GFP_KERNEL);
if (radeon_crtc == NULL)
- return;
+ return -ENOMEM;
+
+ wq = alloc_workqueue("radeon-crtc", WQ_HIGHPRI, 0);
+ if (unlikely(!wq)) {
+ kfree(radeon_crtc);
+ return - ENOMEM;
+ }

drm_crtc_init(dev, &radeon_crtc->base, &radeon_crtc_funcs);

drm_mode_crtc_set_gamma_size(&radeon_crtc->base, 256);
radeon_crtc->crtc_id = index;
- radeon_crtc->flip_queue = alloc_workqueue("radeon-crtc", WQ_HIGHPRI, 0);
+ radeon_crtc->flip_queue = wq;
+
rdev->mode_info.crtcs[index] = radeon_crtc;

if (rdev->family >= CHIP_BONAIRE) {
@@ -711,6 +719,8 @@ static void radeon_crtc_init(struct drm_device *dev, int index)
radeon_atombios_init_crtc(dev, radeon_crtc);
else
radeon_legacy_init_crtc(dev, radeon_crtc);
+
+ return 0;
}

static const char *encoder_names[38] = {
@@ -1602,9 +1612,8 @@ int radeon_modeset_init(struct radeon_device *rdev)
rdev->ddev->mode_config.fb_base = rdev->mc.aper_base;

ret = radeon_modeset_create_props(rdev);
- if (ret) {
- return ret;
- }
+ if (ret)
+ goto err_drm_mode_config_cleanup;

/* init i2c buses */
radeon_i2c_init(rdev);
@@ -1617,7 +1626,9 @@ int radeon_modeset_init(struct radeon_device *rdev)

/* allocate crtcs */
for (i = 0; i < rdev->num_crtc; i++) {
- radeon_crtc_init(rdev->ddev, i);
+ ret = radeon_crtc_init(rdev->ddev, i);
+ if (ret)
+ goto err_drm_mode_config_cleanup;
}

/* okay we should have all the bios connectors */
@@ -1645,6 +1656,10 @@ int radeon_modeset_init(struct radeon_device *rdev)
ret = radeon_pm_late_init(rdev);

return 0;
+
+err_drm_mode_config_cleanup:
+ drm_mode_config_cleanup(rdev->ddev);
+ return ret;
}

void radeon_modeset_fini(struct radeon_device *rdev)