* [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED()
@ 2018-07-11 19:17 Steven Rostedt
2018-07-11 19:38 ` Hans de Goede
2018-07-12 1:58 ` Sergey Senozhatsky
0 siblings, 2 replies; 7+ messages in thread
From: Steven Rostedt @ 2018-07-11 19:17 UTC (permalink / raw)
To: LKML
Cc: Petr Mladek, Sergey Senozhatsky, Hans de Goede, Daniel Vetter,
Thomas Zimmermann, Bartlomiej Zolnierkiewicz, Andrew Morton
From: Steven Rostedt (VMware) <rostedt@goodmis.org>
There's been discussion on the fb list about the addition of
WARN_CONSOLE_UNLOCKED() inside the fb code. The complaint is that when
the fb module is loaded with lockless_register_fb the console lock is
not taken for debugging reasons. With the addition of
WARN_CONSOLE_UNLOCK() within the fb code, this causes the console to
fill up with warnings when trying to debug the fb driver.
There's also a #if 1 that enables the warning which was added before
git history, and we look down on constant #if's in the kernel nowadays
anyway.
Remove the #if 1 and add a ignore_console_lock_warning boolean that can
be set by drivers to ignore the warning in order to do debugging.
Link: http://lkml.kernel.org/r/717e6337-e7a6-7a92-1c1b-8929a25696b5@suse.de
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
diff --git a/include/linux/console.h b/include/linux/console.h
index dfd6b0e97855..9d4a6b985154 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -200,11 +200,9 @@ void vcs_make_sysfs(int index);
void vcs_remove_sysfs(int index);
/* Some debug stub to catch some of the obvious races in the VT code */
-#if 1
-#define WARN_CONSOLE_UNLOCKED() WARN_ON(!is_console_locked() && !oops_in_progress)
-#else
-#define WARN_CONSOLE_UNLOCKED()
-#endif
+extern bool ignore_console_lock_warning;
+#define WARN_CONSOLE_UNLOCKED() \
+ WARN_ON(!ignore_console_lock_warning && !is_console_locked() && !oops_in_progress)
/* VESA Blanking Levels */
#define VESA_NO_BLANKING 0
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 247808333ba4..d9056efc3739 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -66,6 +66,9 @@ int console_printk[4] = {
CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
};
+bool ignore_console_lock_warning __read_mostly;
+EXPORT_SYMBOL(ignore_console_lock_warning);
+
/*
* Low level drivers may need that to know if they can schedule in
* their unblank() callback or not. So let's export it.
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED()
2018-07-11 19:17 [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED() Steven Rostedt
@ 2018-07-11 19:38 ` Hans de Goede
2018-07-12 1:58 ` Sergey Senozhatsky
1 sibling, 0 replies; 7+ messages in thread
From: Hans de Goede @ 2018-07-11 19:38 UTC (permalink / raw)
To: Steven Rostedt, LKML
Cc: Petr Mladek, Sergey Senozhatsky, Daniel Vetter,
Thomas Zimmermann, Bartlomiej Zolnierkiewicz, Andrew Morton
Hi,
On 11-07-18 21:17, Steven Rostedt wrote:
>
> From: Steven Rostedt (VMware) <rostedt@goodmis.org>
>
> There's been discussion on the fb list about the addition of
> WARN_CONSOLE_UNLOCKED() inside the fb code. The complaint is that when
> the fb module is loaded with lockless_register_fb the console lock is
> not taken for debugging reasons. With the addition of
> WARN_CONSOLE_UNLOCK() within the fb code, this causes the console to
> fill up with warnings when trying to debug the fb driver.
>
> There's also a #if 1 that enables the warning which was added before
> git history, and we look down on constant #if's in the kernel nowadays
> anyway.
>
> Remove the #if 1 and add a ignore_console_lock_warning boolean that can
> be set by drivers to ignore the warning in order to do debugging.
>
> Link: http://lkml.kernel.org/r/717e6337-e7a6-7a92-1c1b-8929a25696b5@suse.de
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Based on the fbdev discussion this seems a good idea to me
and codewise this looks good to:
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Regards,
Hans
> ---
> diff --git a/include/linux/console.h b/include/linux/console.h
> index dfd6b0e97855..9d4a6b985154 100644
> --- a/include/linux/console.h
> +++ b/include/linux/console.h
> @@ -200,11 +200,9 @@ void vcs_make_sysfs(int index);
> void vcs_remove_sysfs(int index);
>
> /* Some debug stub to catch some of the obvious races in the VT code */
> -#if 1
> -#define WARN_CONSOLE_UNLOCKED() WARN_ON(!is_console_locked() && !oops_in_progress)
> -#else
> -#define WARN_CONSOLE_UNLOCKED()
> -#endif
> +extern bool ignore_console_lock_warning;
> +#define WARN_CONSOLE_UNLOCKED() \
> + WARN_ON(!ignore_console_lock_warning && !is_console_locked() && !oops_in_progress)
>
> /* VESA Blanking Levels */
> #define VESA_NO_BLANKING 0
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 247808333ba4..d9056efc3739 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -66,6 +66,9 @@ int console_printk[4] = {
> CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
> };
>
> +bool ignore_console_lock_warning __read_mostly;
> +EXPORT_SYMBOL(ignore_console_lock_warning);
> +
> /*
> * Low level drivers may need that to know if they can schedule in
> * their unblank() callback or not. So let's export it.
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED()
2018-07-11 19:17 [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED() Steven Rostedt
2018-07-11 19:38 ` Hans de Goede
@ 2018-07-12 1:58 ` Sergey Senozhatsky
2018-07-12 3:09 ` Steven Rostedt
1 sibling, 1 reply; 7+ messages in thread
From: Sergey Senozhatsky @ 2018-07-12 1:58 UTC (permalink / raw)
To: Steven Rostedt
Cc: LKML, Petr Mladek, Sergey Senozhatsky, Hans de Goede,
Daniel Vetter, Thomas Zimmermann, Bartlomiej Zolnierkiewicz,
Andrew Morton
On (07/11/18 15:17), Steven Rostedt wrote:
> +bool ignore_console_lock_warning __read_mostly;
> +EXPORT_SYMBOL(ignore_console_lock_warning);
OK. So, to recap,
We made is_console_locked() EXPORT_SYMBOL recently [it's still in linux-next],
so people could use WARN_CONSOLE_UNLOCKED in more places; this made other
people unhappy, so now we add another EXPORT_SYMBOL to the picture, which will
disable those newly added WARN_CONSOLE_UNLOCKED and make other people happy
again.
This makes me wonder - do we want to add more WARN_CONSOLE_UNLOCKED in the
first place? :)
Other than that, the patch looks OK to me I guess. I'm not super happy with
more printk EXPORT_SYMBOL-s, frankly speaking, I'm not entirely in love with
the "add a bool flag to suppress warn print outs which we added in the
previous patch" direction, but if you guys want/need it...
Probably I'm just dramatizing it, as usual ;)
The removal of "#if 1" is definitely nice.
Let's hear from Petr.
-ss
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED()
2018-07-12 1:58 ` Sergey Senozhatsky
@ 2018-07-12 3:09 ` Steven Rostedt
2018-07-12 4:25 ` Sergey Senozhatsky
0 siblings, 1 reply; 7+ messages in thread
From: Steven Rostedt @ 2018-07-12 3:09 UTC (permalink / raw)
To: Sergey Senozhatsky
Cc: LKML, Petr Mladek, Sergey Senozhatsky, Hans de Goede,
Daniel Vetter, Thomas Zimmermann, Bartlomiej Zolnierkiewicz,
Andrew Morton
On Thu, 12 Jul 2018 10:58:48 +0900
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote:
> On (07/11/18 15:17), Steven Rostedt wrote:
> > +bool ignore_console_lock_warning __read_mostly;
> > +EXPORT_SYMBOL(ignore_console_lock_warning);
>
> OK. So, to recap,
> We made is_console_locked() EXPORT_SYMBOL recently [it's still in linux-next],
> so people could use WARN_CONSOLE_UNLOCKED in more places; this made other
> people unhappy, so now we add another EXPORT_SYMBOL to the picture, which will
> disable those newly added WARN_CONSOLE_UNLOCKED and make other people happy
> again.
Note, it only made people that added a module parameter that disables
grabbing the console lock in the first place for debugging purposes
only. The added WARN_CONSOLE_UNLOCKED() are good. Nobody complaining
that they exist. They are complaining that it breaks one of their
debugging work flows, and need to disable it when they are doing so.
>
> This makes me wonder - do we want to add more WARN_CONSOLE_UNLOCKED in the
> first place? :)
I would say yes.
>
> Other than that, the patch looks OK to me I guess. I'm not super happy with
> more printk EXPORT_SYMBOL-s, frankly speaking, I'm not entirely in love with
> the "add a bool flag to suppress warn print outs which we added in the
> previous patch" direction, but if you guys want/need it...
I could add a comment explaining why it exists. Something like:
/*
* Set this is you need to quiet WARN_CONSOLE_UNLOCKED() for debugging
* purposes.
*/
> Probably I'm just dramatizing it, as usual ;)
> The removal of "#if 1" is definitely nice.
Yeah, that had to go regardless.
>
> Let's hear from Petr.
Sure.
-- Steve
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED()
2018-07-12 3:09 ` Steven Rostedt
@ 2018-07-12 4:25 ` Sergey Senozhatsky
2018-07-12 7:53 ` Petr Mladek
0 siblings, 1 reply; 7+ messages in thread
From: Sergey Senozhatsky @ 2018-07-12 4:25 UTC (permalink / raw)
To: Steven Rostedt
Cc: Sergey Senozhatsky, LKML, Petr Mladek, Sergey Senozhatsky,
Hans de Goede, Daniel Vetter, Thomas Zimmermann,
Bartlomiej Zolnierkiewicz, Andrew Morton
On (07/11/18 23:09), Steven Rostedt wrote:
> > On (07/11/18 15:17), Steven Rostedt wrote:
> > > +bool ignore_console_lock_warning __read_mostly;
> > > +EXPORT_SYMBOL(ignore_console_lock_warning);
> >
> > OK. So, to recap,
> > We made is_console_locked() EXPORT_SYMBOL recently [it's still in linux-next],
> > so people could use WARN_CONSOLE_UNLOCKED in more places; this made other
> > people unhappy, so now we add another EXPORT_SYMBOL to the picture, which will
> > disable those newly added WARN_CONSOLE_UNLOCKED and make other people happy
> > again.
>
> Note, it only made people that added a module parameter that disables
> grabbing the console lock in the first place for debugging purposes
> only. The added WARN_CONSOLE_UNLOCKED() are good. Nobody complaining
> that they exist. They are complaining that it breaks one of their
> debugging work flows, and need to disable it when they are doing so.
True, but at the same time nobody complained that we didn't have those
extra WARN_CONSOLE_UNLOCKED()-s. Just saying. Over all I agree that there
is probably some value in those extra WARN-s.
> I could add a comment explaining why it exists. Something like:
>
> /*
> * Set this is you need to quiet WARN_CONSOLE_UNLOCKED() for debugging
> * purposes.
> */
s/is you/if you/
Suggested-by: One-of-those-commiters@YouKnowWhoYouAre.org ;)
-ss
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED()
2018-07-12 4:25 ` Sergey Senozhatsky
@ 2018-07-12 7:53 ` Petr Mladek
2018-07-12 8:09 ` Sergey Senozhatsky
0 siblings, 1 reply; 7+ messages in thread
From: Petr Mladek @ 2018-07-12 7:53 UTC (permalink / raw)
To: Sergey Senozhatsky
Cc: Steven Rostedt, LKML, Sergey Senozhatsky, Hans de Goede,
Daniel Vetter, Thomas Zimmermann, Bartlomiej Zolnierkiewicz,
Andrew Morton
On Thu 2018-07-12 13:25:52, Sergey Senozhatsky wrote:
> On (07/11/18 23:09), Steven Rostedt wrote:
> > > On (07/11/18 15:17), Steven Rostedt wrote:
> > > > +bool ignore_console_lock_warning __read_mostly;
> > > > +EXPORT_SYMBOL(ignore_console_lock_warning);
> > >
> > > OK. So, to recap,
> > > We made is_console_locked() EXPORT_SYMBOL recently [it's still in linux-next],
> > > so people could use WARN_CONSOLE_UNLOCKED in more places; this made other
> > > people unhappy, so now we add another EXPORT_SYMBOL to the picture, which will
> > > disable those newly added WARN_CONSOLE_UNLOCKED and make other people happy
> > > again.
> >
> > Note, it only made people that added a module parameter that disables
> > grabbing the console lock in the first place for debugging purposes
> > only. The added WARN_CONSOLE_UNLOCKED() are good. Nobody complaining
> > that they exist. They are complaining that it breaks one of their
> > debugging work flows, and need to disable it when they are doing so.
>
> True, but at the same time nobody complained that we didn't have those
> extra WARN_CONSOLE_UNLOCKED()-s. Just saying. Over all I agree that there
> is probably some value in those extra WARN-s.
I agree that there is some value in the extra WARN's. Also it seems
that it is useful to disable them for debugging purposes. I do not
see a better solution. Therefore I am fine with this one.
> > I could add a comment explaining why it exists. Something like:
> >
> > /*
> > * Set this is you need to quiet WARN_CONSOLE_UNLOCKED() for debugging
> > * purposes.
> > */
>
> s/is you/if you/
Yes, this extra comment would be appreciated.
If you send v2, please, break also the WARN definition to 80-chars's
per line ;-)
> Suggested-by: One-of-those-commiters@YouKnowWhoYouAre.org ;)
AFAIK, the change was actually suggested by Steven. The inspiration
is described by the line:
Link:
http://lkml.kernel.org/r/717e6337-e7a6-7a92-1c1b-8929a25696b5@suse.de
Finally, IMHO, it would make sense to push this change together with
the fbcon/vt side.
Best Regards,
Petr
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED()
2018-07-12 7:53 ` Petr Mladek
@ 2018-07-12 8:09 ` Sergey Senozhatsky
0 siblings, 0 replies; 7+ messages in thread
From: Sergey Senozhatsky @ 2018-07-12 8:09 UTC (permalink / raw)
To: Petr Mladek
Cc: Sergey Senozhatsky, Steven Rostedt, LKML, Sergey Senozhatsky,
Hans de Goede, Daniel Vetter, Thomas Zimmermann,
Bartlomiej Zolnierkiewicz, Andrew Morton
On (07/12/18 09:53), Petr Mladek wrote:
> >
> > True, but at the same time nobody complained that we didn't have those
> > extra WARN_CONSOLE_UNLOCKED()-s. Just saying. Over all I agree that there
> > is probably some value in those extra WARN-s.
>
> I agree that there is some value in the extra WARN's. Also it seems
> that it is useful to disable them for debugging purposes. I do not
> see a better solution. Therefore I am fine with this one.
Good.
> Yes, this extra comment would be appreciated.
Yep.
> If you send v2, please, break also the WARN definition to 80-chars's
> per line ;-)
Yeah, I noticed that too.
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
-ss
^ permalink raw reply [flat|nested] 7+ messages in thread
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2018-07-11 19:17 [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE_UNLOCKED() Steven Rostedt
2018-07-11 19:38 ` Hans de Goede
2018-07-12 1:58 ` Sergey Senozhatsky
2018-07-12 3:09 ` Steven Rostedt
2018-07-12 4:25 ` Sergey Senozhatsky
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