On Fri, Jun 25, 2021 at 02:36:23PM +0200, Petr Mladek wrote: > On Thu 2021-06-24 13:17:46, John Ogness wrote: > > All NMI contexts are handled the same as the safe context: store the > > message and defer printing. There is no need to have special NMI > > context tracking for this. Using in_nmi() is enough. > > > > Signed-off-by: John Ogness <john.ogn...@linutronix.de> > > Reviewed-by: Petr Mladek <pmla...@suse.com> > > --- > > arch/arm/kernel/smp.c | 2 -- > > arch/powerpc/kexec/crash.c | 3 --- > > include/linux/hardirq.h | 2 -- > > include/linux/printk.h | 12 ------------ > > init/Kconfig | 5 ----- > > kernel/printk/internal.h | 6 ------ > > kernel/printk/printk_safe.c | 37 +------------------------------------ > > kernel/trace/trace.c | 2 -- > > 8 files changed, 1 insertion(+), 68 deletions(-) > > > > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c > > index 74679240a9d8..0dd2d733ad62 100644 > > --- a/arch/arm/kernel/smp.c > > +++ b/arch/arm/kernel/smp.c > > @@ -668,9 +668,7 @@ static void do_handle_IPI(int ipinr) > > break; > > > > case IPI_CPU_BACKTRACE: > > - printk_nmi_enter(); > > nmi_cpu_backtrace(get_irq_regs()); > > - printk_nmi_exit(); > > It looks to me that in_nmi() returns false here. As a result, > nmi_cpu_backtrace() might newly call consoles immediately. > > If I recall correctly, arm does not have a proper NMI. > And this is just some special case of a "normal" IRQ. > > And indeed, nmi_enter() is called only from handle_fiq_as_nmi() > and it is just a boiler plate. > > If I am right, we should replace printk_nmi_enter() with > printk_safe_enter_irqsave(flags) or so. > > Even better solution might be to call this within > nmi_enter()/nmi_exit(). But I am not sure if this is what > the arm people want.
As I seem to recall, the guy in ARM Ltd who was working on this seemed to drift away and it never got finished - however, I've always carried platform specific hacks in my tree to make this work from FIQ on the platforms I cared about: http://git.armlinux.org.uk/cgit/linux-arm.git/commit/?h=fiq Not suitable for mainline like that. I'm not aware of anyone working on it now. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
