Hi,
On 09-08-18 12:03, Bartlomiej Zolnierkiewicz wrote:
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@xxxxxxxxxx>
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.
Ok I will send a v2 which adds a comment why we need to use in_atomic
here.
Regards,
Hans
---
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
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