On Thu, 19 Jul 2018 12:16:00 +0200 Thomas Zimmermann <tzimmerm...@suse.de> wrote:
> The macro WARN_CONSOLE_UNLOCKED prints a warning when a thread enters > the console's critical section without having acquired the console > lock. The console lock can be ignored when debugging the console using > printk, but this makes WARN_CONSOLE_UNLOCKED generate unnecessary > warnings. > > The variable ignore_console_lock_warning temporarily disables > WARN_CONSOLE_UNLOCKED. Developers interested in debugging the console's > critical sections should increment it before entering the CS and > decrement it after leaving the CS. Setting ignore_console_lock_warning > is only for debugging. Regular operation should not manipulate it. > > Acknoledgements: This patch is based on an earlier version by Steven > Rostedt. The use of atomic increment/decrement was suggested by Petr > Mladek. You can also add a reference to that patch as well: Link: http://lkml.kernel.org/r/20180712092938.22e33...@gandalf.local.home -- Steve > > Link: http://lkml.kernel.org/r/717e6337-e7a6-7a92-1c1b-8929a2569...@suse.de > Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de> > --- > include/linux/console.h | 14 +++++++++----- > kernel/printk/printk.c | 3 +++ > 2 files changed, 12 insertions(+), 5 deletions(-) > > diff --git a/include/linux/console.h b/include/linux/console.h > index f59f3dbca65c..a3307bcab947 100644 > --- a/include/linux/console.h > +++ b/include/linux/console.h > @@ -14,6 +14,7 @@ > #ifndef _LINUX_CONSOLE_H_ > #define _LINUX_CONSOLE_H_ 1 > > +#include <asm/atomic.h> > #include <linux/types.h> > > struct vc_data; > @@ -201,11 +202,14 @@ 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 > +#define WARN_CONSOLE_UNLOCKED() > \ > + WARN_ON(!atomic_read(&ignore_console_lock_warning) && \ > + !is_console_locked() && !oops_in_progress) > +/* > + * Increment ignore_console_lock_warning if you need to quiet > + * WARN_CONSOLE_UNLOCKED() for debugging purposes. > + */ > +extern atomic_t ignore_console_lock_warning; > > /* VESA Blanking Levels */ > #define VESA_NO_BLANKING 0 > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > index 3f041e7cbfc9..7d32a86758cd 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 */ > }; > > +atomic_t ignore_console_lock_warning __read_mostly = ATOMIC_INIT(0); > +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. _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
