* [PATCH] drm/fb-helper: Add locking to sysrq handling
@ 2020-10-07 13:30 Daniel Vetter
2020-10-08 9:22 ` Thomas Zimmermann
0 siblings, 1 reply; 3+ messages in thread
From: Daniel Vetter @ 2020-10-07 13:30 UTC (permalink / raw)
To: DRI Development
Cc: David Airlie, Daniel Vetter, Intel Graphics Development,
Thomas Zimmermann, Daniel Vetter
We didn't take the kernel_fb_helper_lock mutex, which protects that
code. While at it, simplify the code
- inline the function (originally shared with kgdb I think)
- drop the error tracking and all the complications
- drop the pointless early out, it served nothing
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
---
drivers/gpu/drm/drm_fb_helper.c | 26 +++++---------------------
1 file changed, 5 insertions(+), 21 deletions(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 8697554ccd41..c2f72bb6afb1 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -281,18 +281,12 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked);
#ifdef CONFIG_MAGIC_SYSRQ
-/*
- * restore fbcon display for all kms driver's using this helper, used for sysrq
- * and panic handling.
- */
-static bool drm_fb_helper_force_kernel_mode(void)
+/* emergency restore, don't bother with error reporting */
+static void drm_fb_helper_restore_work_fn(struct work_struct *ignored)
{
- bool ret, error = false;
struct drm_fb_helper *helper;
- if (list_empty(&kernel_fb_helper_list))
- return false;
-
+ mutex_lock(&kernel_fb_helper_lock);
list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) {
struct drm_device *dev = helper->dev;
@@ -300,22 +294,12 @@ static bool drm_fb_helper_force_kernel_mode(void)
continue;
mutex_lock(&helper->lock);
- ret = drm_client_modeset_commit_locked(&helper->client);
- if (ret)
- error = true;
+ drm_client_modeset_commit_locked(&helper->client);
mutex_unlock(&helper->lock);
}
- return error;
+ mutex_unlock(&kernel_fb_helper_lock);
}
-static void drm_fb_helper_restore_work_fn(struct work_struct *ignored)
-{
- bool ret;
-
- ret = drm_fb_helper_force_kernel_mode();
- if (ret == true)
- DRM_ERROR("Failed to restore crtc configuration\n");
-}
static DECLARE_WORK(drm_fb_helper_restore_work, drm_fb_helper_restore_work_fn);
static void drm_fb_helper_sysrq(int dummy1)
--
2.28.0
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^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] drm/fb-helper: Add locking to sysrq handling
2020-10-07 13:30 [PATCH] drm/fb-helper: Add locking to sysrq handling Daniel Vetter
@ 2020-10-08 9:22 ` Thomas Zimmermann
2020-10-08 9:29 ` Daniel Vetter
0 siblings, 1 reply; 3+ messages in thread
From: Thomas Zimmermann @ 2020-10-08 9:22 UTC (permalink / raw)
To: Daniel Vetter, DRI Development
Cc: David Airlie, Intel Graphics Development, Daniel Vetter
[-- Attachment #1.1.1: Type: text/plain, Size: 3019 bytes --]
Hi
Am 07.10.20 um 15:30 schrieb Daniel Vetter:
> We didn't take the kernel_fb_helper_lock mutex, which protects that
> code. While at it, simplify the code
> - inline the function (originally shared with kgdb I think)
> - drop the error tracking and all the complications
> - drop the pointless early out, it served nothing
>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> ---
> drivers/gpu/drm/drm_fb_helper.c | 26 +++++---------------------
> 1 file changed, 5 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 8697554ccd41..c2f72bb6afb1 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -281,18 +281,12 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
> EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked);
>
> #ifdef CONFIG_MAGIC_SYSRQ
> -/*
> - * restore fbcon display for all kms driver's using this helper, used for sysrq
> - * and panic handling.
> - */
> -static bool drm_fb_helper_force_kernel_mode(void)
> +/* emergency restore, don't bother with error reporting */
> +static void drm_fb_helper_restore_work_fn(struct work_struct *ignored)
> {
> - bool ret, error = false;
> struct drm_fb_helper *helper;
>
> - if (list_empty(&kernel_fb_helper_list))
> - return false;
> -
> + mutex_lock(&kernel_fb_helper_lock);
> list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) {
> struct drm_device *dev = helper->dev;
>
> @@ -300,22 +294,12 @@ static bool drm_fb_helper_force_kernel_mode(void)
> continue;
>
> mutex_lock(&helper->lock);
> - ret = drm_client_modeset_commit_locked(&helper->client);
> - if (ret)
> - error = true;
> + drm_client_modeset_commit_locked(&helper->client);
> mutex_unlock(&helper->lock);
> }
> - return error;
> + mutex_unlock(&kernel_fb_helper_lock);
> }
>
> -static void drm_fb_helper_restore_work_fn(struct work_struct *ignored)
> -{
> - bool ret;
> -
> - ret = drm_fb_helper_force_kernel_mode();
> - if (ret == true)
> - DRM_ERROR("Failed to restore crtc configuration\n");
Is there a specific reason for removing that warning? Even if it doesn't
show up on screen, is it not helpful in the kernel's log?
In any case, the rest looks good.
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Best regards
Thomas
> -}
> static DECLARE_WORK(drm_fb_helper_restore_work, drm_fb_helper_restore_work_fn);
>
> static void drm_fb_helper_sysrq(int dummy1)
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] drm/fb-helper: Add locking to sysrq handling
2020-10-08 9:22 ` Thomas Zimmermann
@ 2020-10-08 9:29 ` Daniel Vetter
0 siblings, 0 replies; 3+ messages in thread
From: Daniel Vetter @ 2020-10-08 9:29 UTC (permalink / raw)
To: Thomas Zimmermann
Cc: David Airlie, Intel Graphics Development, DRI Development, Daniel Vetter
On Thu, Oct 8, 2020 at 11:22 AM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>
> Hi
>
> Am 07.10.20 um 15:30 schrieb Daniel Vetter:
> > We didn't take the kernel_fb_helper_lock mutex, which protects that
> > code. While at it, simplify the code
> > - inline the function (originally shared with kgdb I think)
> > - drop the error tracking and all the complications
> > - drop the pointless early out, it served nothing
> >
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Maxime Ripard <mripard@kernel.org>
> > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > Cc: David Airlie <airlied@linux.ie>
> > Cc: Daniel Vetter <daniel@ffwll.ch>
> > ---
> > drivers/gpu/drm/drm_fb_helper.c | 26 +++++---------------------
> > 1 file changed, 5 insertions(+), 21 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> > index 8697554ccd41..c2f72bb6afb1 100644
> > --- a/drivers/gpu/drm/drm_fb_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > @@ -281,18 +281,12 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
> > EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked);
> >
> > #ifdef CONFIG_MAGIC_SYSRQ
> > -/*
> > - * restore fbcon display for all kms driver's using this helper, used for sysrq
> > - * and panic handling.
> > - */
> > -static bool drm_fb_helper_force_kernel_mode(void)
> > +/* emergency restore, don't bother with error reporting */
> > +static void drm_fb_helper_restore_work_fn(struct work_struct *ignored)
> > {
> > - bool ret, error = false;
> > struct drm_fb_helper *helper;
> >
> > - if (list_empty(&kernel_fb_helper_list))
> > - return false;
> > -
> > + mutex_lock(&kernel_fb_helper_lock);
> > list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) {
> > struct drm_device *dev = helper->dev;
> >
> > @@ -300,22 +294,12 @@ static bool drm_fb_helper_force_kernel_mode(void)
> > continue;
> >
> > mutex_lock(&helper->lock);
> > - ret = drm_client_modeset_commit_locked(&helper->client);
> > - if (ret)
> > - error = true;
> > + drm_client_modeset_commit_locked(&helper->client);
> > mutex_unlock(&helper->lock);
> > }
> > - return error;
> > + mutex_unlock(&kernel_fb_helper_lock);
> > }
> >
> > -static void drm_fb_helper_restore_work_fn(struct work_struct *ignored)
> > -{
> > - bool ret;
> > -
> > - ret = drm_fb_helper_force_kernel_mode();
> > - if (ret == true)
> > - DRM_ERROR("Failed to restore crtc configuration\n");
>
> Is there a specific reason for removing that warning? Even if it doesn't
> show up on screen, is it not helpful in the kernel's log?
I just found it really unhelpful, if you're trying to force-show
fbcon, what's the point if it doesn't work out? The user will notice.
Also, if we're really in a dire situation where you want this, in my
experience there's a bunch of random other reasons why this can fail,
mostly when the work we have to schedule for locking reasons never
runs. So it's also unreliable.
> In any case, the rest looks good.
>
> Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Thanks for taking a look, I'll apply it.
-Daniel
>
> Best regards
> Thomas
>
> > -}
> > static DECLARE_WORK(drm_fb_helper_restore_work, drm_fb_helper_restore_work_fn);
> >
> > static void drm_fb_helper_sysrq(int dummy1)
> >
>
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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