On Thu 2015-12-17 14:38:58, Andrew Morton wrote: > On Tue, 15 Dec 2015 15:26:21 +0100 Petr Mladek <pmladek@xxxxxxxx> wrote: > > > > OK, thanks. So "not needed at present, might be needed in the future, > > > useful for out-of-tree debug code"? > > > > It is possible that I got it a wrong way on arm. The NMI buffer is > > usable there on two locations. > > > > First, the temporary is currently used to handle IPI_CPU_BACKTRACE. > > It seems that it is not a real NMI. But it seems to be available > > (compiled) on all arm system. This is why I introduced NEED_PRINTK_NMI > > Kconfig flag to avoid confusion with a real NMI. > > > > Second, there is the FIQ "NMI" handler that is called from > > /arch/arm/kernel/entry-armv.S. It is compiled only if _not_ > > defined $(CONFIG_CPU_V7M). It calls nmi_enter() and nmi_stop(). > > It looks like a real NMI handler. This is why I defined HAVE_NMI > > if (!CPU_V7M). > > > > A solution would be to define HAVE_NMI on all Arm systems and get rid > > of NEED_PRINTK_NMI. If you think that it would cause less confusion... > > So does this mean that the patch will be updated? Please, find the follow up patch below. I guess that you will want to squash it into the [1/n] one. >From 144d90ada2e34b8807efcc01922c48d7c09797e7 Mon Sep 17 00:00:00 2001 From: Petr Mladek <pmladek@xxxxxxxx> Date: Fri, 18 Dec 2015 16:04:35 +0100 Subject: [PATCH] printk/nmi: Remove the questionable CONFIG_NEED_PRINTK_NMI The flag NEED_PRINTK_NMI was added because of Arm. It used the NMI safe backtrace implementation on all Arm systems. But it did not have a real NMI handling on CPU_V7M. It seems that it causes more confusion than good. Let's use HAVE_NMI on all arm systems and get rid of the problematic flag. Signed-off-by: Petr Mladek <pmladek@xxxxxxxx> --- arch/Kconfig | 3 --- arch/arm/Kconfig | 3 +-- init/Kconfig | 2 +- 3 files changed, 2 insertions(+), 6 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 7ce5101c2472..d1a18b313624 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -190,9 +190,6 @@ config HAVE_KPROBES_ON_FTRACE config HAVE_NMI bool -config NEED_PRINTK_NMI - bool - config HAVE_NMI_WATCHDOG depends on HAVE_NMI bool diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 96d2c275f0f7..01dc56d8f31b 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -63,8 +63,7 @@ config ARM select HAVE_KRETPROBES if (HAVE_KPROBES) select HAVE_MEMBLOCK select HAVE_MOD_ARCH_SPECIFIC - select HAVE_NMI if (!CPU_V7M) - select NEED_PRINTK_NMI if (CPU_V7M) + select HAVE_NMI select HAVE_OPROFILE if (HAVE_PERF_EVENTS) select HAVE_OPTPROBES if !THUMB2_KERNEL select HAVE_PERF_EVENTS diff --git a/init/Kconfig b/init/Kconfig index 61cfd96a3c96..abf79f3b1a55 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1481,7 +1481,7 @@ config PRINTK config PRINTK_NMI def_bool y depends on PRINTK - depends on HAVE_NMI || NEED_PRINTK_NMI + depends on HAVE_NMI config BUG bool "BUG() support" if EXPERT -- 1.8.5.6 -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
