Re: [PATCH v4 05/27] x86: Replace ist_enter() with nmi_enter()

Peter Zijlstra
2020-02-26T10:25:46Z

On Mon, Feb 24, 2020 at 05:02:31PM -0500, Steven Rostedt wrote:
> On Mon, 24 Feb 2020 22:31:39 +0100
> Peter Zijlstra <peterz@infradead.org> wrote:
>
> > > Just want to confirm that printk_nmi_enter(), lockdep_off(),
> > > and ftrace_nmi_enter() are all marked fully with NOKPROBE.
> >
> > *sigh*, right you are, I only looked at notrace, not nokprobe.
> >
> > In particular the ftrace one is a bit off a mess, let me sort through
> > that.
>
> ftrace_nmi_enter() has two purposes. One, for archs that need to deal with
> NMIs while they still use stop machine. Although, it appears sh is the only
> arch that does that. I can look to see if it can be ripped out.

Already done :-)

---
Subject: sh/ftrace: Move arch_ftrace_nmi_{enter,exit} into nmi exception
From: Peter Zijlstra <peterz@infradead.org>
Date: Mon Feb 24 22:26:21 CET 2020

SuperH is the last remaining user of arch_ftrace_nmi_{enter,exit}(),
remove it from the generic code and into the SuperH code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
Documentation/trace/ftrace-design.rst | 8 --------
arch/sh/Kconfig | 1 -
arch/sh/kernel/traps.c | 12 ++++++++++++
include/linux/ftrace_irq.h | 11 -----------
kernel/trace/Kconfig | 10 ----------
5 files changed, 12 insertions(+), 30 deletions(-)

--- a/Documentation/trace/ftrace-design.rst
+++ b/Documentation/trace/ftrace-design.rst
@@ -229,14 +229,6 @@ Adding support for it is easy: just defi
pass the return address pointer as the 'retp' argument to
ftrace_push_return_trace().

-HAVE_FTRACE_NMI_ENTER
----------------------
-
-If you can't trace NMI functions, then skip this option.
-
-
-
-
HAVE_SYSCALL_TRACEPOINTS
------------------------

--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -71,7 +71,6 @@ config SUPERH32
select HAVE_FUNCTION_TRACER
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_DYNAMIC_FTRACE
- select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
select ARCH_WANT_IPC_PARSE_VERSION
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_ARCH_KGDB
--- a/arch/sh/kernel/traps.c
+++ b/arch/sh/kernel/traps.c
@@ -170,11 +170,21 @@ BUILD_TRAP_HANDLER(bug)
force_sig(SIGTRAP);
}

+#ifdef CONFIG_HAVE_DYNAMIC_FTRACE
+extern void arch_ftrace_nmi_enter(void);
+extern void arch_ftrace_nmi_exit(void);
+#else
+static inline void arch_ftrace_nmi_enter(void) { }
+static inline void arch_ftrace_nmi_exit(void) { }
+#endif
+
BUILD_TRAP_HANDLER(nmi)
{
unsigned int cpu = smp_processor_id();
TRAP_HANDLER_DECL;

+ arch_ftrace_nmi_enter();
+
nmi_enter();
nmi_count(cpu)++;

@@ -190,4 +200,6 @@ BUILD_TRAP_HANDLER(nmi)
}

nmi_exit();
+
+ arch_ftrace_nmi_exit();
}
--- a/include/linux/ftrace_irq.h
+++ b/include/linux/ftrace_irq.h
@@ -2,15 +2,6 @@
#ifndef _LINUX_FTRACE_IRQ_H
#define _LINUX_FTRACE_IRQ_H

-
-#ifdef CONFIG_FTRACE_NMI_ENTER
-extern void arch_ftrace_nmi_enter(void);
-extern void arch_ftrace_nmi_exit(void);
-#else
-static inline void arch_ftrace_nmi_enter(void) { }
-static inline void arch_ftrace_nmi_exit(void) { }
-#endif
-
#ifdef CONFIG_HWLAT_TRACER
extern bool trace_hwlat_callback_enabled;
extern void trace_hwlat_callback(bool enter);
@@ -22,12 +13,10 @@ static inline void ftrace_nmi_enter(void
if (trace_hwlat_callback_enabled)
trace_hwlat_callback(true);
#endif
- arch_ftrace_nmi_enter();
}

static inline void ftrace_nmi_exit(void)
{
- arch_ftrace_nmi_exit();
#ifdef CONFIG_HWLAT_TRACER
if (trace_hwlat_callback_enabled)
trace_hwlat_callback(false);
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -10,11 +10,6 @@ config USER_STACKTRACE_SUPPORT
config NOP_TRACER
bool

-config HAVE_FTRACE_NMI_ENTER
- bool
- help
- See Documentation/trace/ftrace-design.rst
-
config HAVE_FUNCTION_TRACER
bool
help
@@ -72,11 +67,6 @@ config RING_BUFFER
select TRACE_CLOCK
select IRQ_WORK

-config FTRACE_NMI_ENTER
- bool
- depends on HAVE_FTRACE_NMI_ENTER
- default y
-
config EVENT_TRACING
select CONTEXT_SWITCH_TRACER
select GLOB