On Monday, August 06, 2018 05:54:16 PM Hans de Goede wrote:
Taking over the console involves allocating mem with GFP_KERNEL, talking to drm drivers, etc. So this should not be done from an atomic context.
But the console-output trigger deferred console takeover may happen from an atomic context, which leads to "BUG: sleeping function called from invalid context" errors.
This commit fixes these errors by doing the deferred takeover from a workqueue when the notifier runs from an atomic context.
Signed-off-by: Hans de Goede hdegoede@redhat.com
checkpatch.pl complains about in_atomic use:
ERROR: do not use in_atomic in drivers #51: FILE: drivers/video/fbdev/core/fbcon.c:3623: + if (in_atomic() || irqs_disabled()) {
please also see the comment in preempt.h:
/* * Are we running in atomic context? WARNING: this macro cannot * always detect atomic context; in particular, it cannot know about * held spinlocks in non-preemptible kernels. Thus it should not be * used in the general case to determine whether sleeping is possible. * Do not use in_atomic() in driver code. */ #define in_atomic() (preempt_count() != 0)
Therefore please explain why it is fine to use in_atomic in fbcon's case.
drivers/video/fbdev/core/fbcon.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index ef8b2d0b7071..4e5997d53fc4 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -3592,7 +3592,20 @@ static int fbcon_init_device(void) }
#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER +static void fbcon_register_existing_fbs(struct work_struct *work) +{
- int i;
- console_lock();
- for_each_registered_fb(i)
fbcon_fb_registered(registered_fb[i]);- console_unlock();
+}
static struct notifier_block fbcon_output_nb; +static DECLARE_WORK(fbcon_deferred_takeover_work, fbcon_register_existing_fbs);
static int fbcon_output_notifier(struct notifier_block *nb, unsigned long action, void *data) @@ -3607,8 +3620,12 @@ static int fbcon_output_notifier(struct notifier_block *nb, deferred_takeover = false; logo_shown = FBCON_LOGO_DONTSHOW;
- for_each_registered_fb(i)
fbcon_fb_registered(registered_fb[i]);
if (in_atomic() || irqs_disabled()) {
schedule_work(&fbcon_deferred_takeover_work);} else {
for_each_registered_fb(i)fbcon_fb_registered(registered_fb[i]);}
return NOTIFY_OK;
}
Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics