On Tuesday, August 15, 2017 4:56:19 AM CEST Sergey Senozhatsky wrote: > We need to switch to emergency printk mode in kernel_kexec(). One > kernel_kexec() branch calls kernel_restart_prepare(), which updates > `system_state', however, the other one, when user requested to > ->preserve_context, does not and we are lacking the information > in printk about kexec being executed. Register a syscore notifier > so printk will be notified by syscore_suspend(). > > Signed-off-by: Sergey Senozhatsky <sergey.senozhat...@gmail.com> > --- > kernel/printk/printk.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > index d3f149fad85c..b14e35f94596 100644 > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -50,6 +50,7 @@ > #include <linux/sched/task_stack.h> > #include <linux/kthread.h> > #include <linux/suspend.h> > +#include <linux/syscore_ops.h> > > #include <linux/uaccess.h> > #include <asm/sections.h> > @@ -2941,6 +2942,22 @@ static struct notifier_block printk_pm_nb = { > .notifier_call = printk_pm_notify, > }; > > +static int printk_syscore_suspend(void) > +{ > + printk_emergency_begin(); > + return 0; > +}
Somebody looking at suspend/resume code paths only will be wondering why you need this, because we should be in the emergency mode already when it is called. It would be good to add a comment about the kexec context here. > + > +static void printk_syscore_resume(void) > +{ > + printk_emergency_end(); > +} This will turn the emergency mode off during resume before the notifier added by the previous patch AFAICS. Is this intentional? Thanks, Rafael