Hi All, On 2/2/24 09:53, Daniel van Vugt wrote: > Until now, deferred console takeover only meant defer until there is > output. But that risks stepping on the toes of userspace splash screens, > as console messages may appear before the splash screen. So check for the > "splash" parameter (as used by Plymouth) and if present then extend the > deferral until the first switch. Daniel, thank you for your patch but I do not believe that this is the right solution. Deferring fbcon takeover further then after the first text is output means that any errors about e.g. a corrupt initrd or the kernel erroring out / crashing will not be visible. When the kernel e.g. oopses or panics because of not finding its rootfs (I tested the latter option when writing the original deferred fbcon takeover code) then fbcon must takeover and print the messages from the dying kernel so that the user has some notion of what is going wrong. And since your patch seems to delay switching till the first vc-switch this means that e.g. even after say gdm refusing to start because of issues there still will be no text output. This makes debugging various issues much harder. Moreover Fedora has been doing flickerfree boot for many years without needing this. The kernel itself will be quiet as long as you set CONFIG_CONSOLE_LOGLEVEL_QUIET=3 Ubuntu atm has set this to 4 which means any kernel pr_err() or dev_err() messages will get through and since there are quite a few false positives of those Ubuntu really needs to set CONFIG_CONSOLE_LOGLEVEL_QUIET=3 to fix part of: https://bugs.launchpad.net/bugs/1970069 After that it is "just" a matter of not making userspace output anything unless it has errors to report. systemd already is quiet by default (only logging errors) when quiet is on the kernel commandline. So any remaining issues are Ubuntu specific boot process bits and Ubuntu really should be able to make those by silent unless they have important info (errors or other unexpected things) to report. Given that this will make debugging boot issues much harder and that there are other IMHO better alternatives I'm nacking this patch: NACK. FWIW I believe that I'm actually saving Ubuntu from shooting themselves in the foot here, hiding all sort of boot errors (like the initrd not finding /) until the user does a magic alt+f2 followed by alt+f1 incantation really is not doing yourself any favors wrt debugging any sort of boot failures. Regards, Hans > Closes: https://bugs.launchpad.net/bugs/1970069 > Cc: Mario Limonciello <mario.limonciello@xxxxxxx> > Signed-off-by: Daniel van Vugt <daniel.van.vugt@xxxxxxxxxxxxx> > --- > drivers/video/fbdev/core/fbcon.c | 32 +++++++++++++++++++++++++++++--- > 1 file changed, 29 insertions(+), 3 deletions(-) > > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c > index 63af6ab034..5b9f7635f7 100644 > --- a/drivers/video/fbdev/core/fbcon.c > +++ b/drivers/video/fbdev/core/fbcon.c > @@ -76,6 +76,7 @@ > #include <linux/crc32.h> /* For counting font checksums */ > #include <linux/uaccess.h> > #include <asm/irq.h> > +#include <asm/cmdline.h> > > #include "fbcon.h" > #include "fb_internal.h" > @@ -146,6 +147,7 @@ static inline void fbcon_map_override(void) > > #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > static bool deferred_takeover = true; > +static int initial_console = -1; > #else > #define deferred_takeover false > #endif > @@ -3341,7 +3343,7 @@ static void fbcon_register_existing_fbs(struct work_struct *work) > console_unlock(); > } > > -static struct notifier_block fbcon_output_nb; > +static struct notifier_block fbcon_output_nb, fbcon_switch_nb; > static DECLARE_WORK(fbcon_deferred_takeover_work, fbcon_register_existing_fbs); > > static int fbcon_output_notifier(struct notifier_block *nb, > @@ -3358,6 +3360,21 @@ static int fbcon_output_notifier(struct notifier_block *nb, > > return NOTIFY_OK; > } > + > +static int fbcon_switch_notifier(struct notifier_block *nb, > + unsigned long action, void *data) > +{ > + struct vc_data *vc = data; > + > + WARN_CONSOLE_UNLOCKED(); > + > + if (vc->vc_num != initial_console) { > + dummycon_unregister_switch_notifier(&fbcon_switch_nb); > + dummycon_register_output_notifier(&fbcon_output_nb); > + } > + > + return NOTIFY_OK; > +} > #endif > > static void fbcon_start(void) > @@ -3370,7 +3387,14 @@ static void fbcon_start(void) > > if (deferred_takeover) { > fbcon_output_nb.notifier_call = fbcon_output_notifier; > - dummycon_register_output_notifier(&fbcon_output_nb); > + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; > + initial_console = fg_console; > + > + if (cmdline_find_option_bool(boot_command_line, "splash")) > + dummycon_register_switch_notifier(&fbcon_switch_nb); > + else > + dummycon_register_output_notifier(&fbcon_output_nb); > + > return; > } > #endif > @@ -3417,8 +3441,10 @@ void __exit fb_console_exit(void) > { > #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > console_lock(); > - if (deferred_takeover) > + if (deferred_takeover) { > dummycon_unregister_output_notifier(&fbcon_output_nb); > + dummycon_unregister_switch_notifier(&fbcon_switch_nb); > + } > console_unlock(); > > cancel_work_sync(&fbcon_deferred_takeover_work);
