From 7f8d61f005228fc48e6e2ca3c9af3302cd4870af Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Thu, 3 Nov 2016 13:09:24 +0100
Subject: [PATCH] percpu: use notrace variant of preempt_disable/preempt_enable

Commit 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap like
events do") added a couple of this_cpu_read calls to the ftrace code.

On x86 this is not a problem, since it has single instructions to read
percpu data. Other architectures which use the generic variant now
have additional preempt_disable and preempt_enable calls in the core
ftrace code. This may lead to recursive calls and in result to a dead
machine, e.g. if preemption and debugging options are enabled.

To fix this use the notrace variant of preempt_disable and
preempt_enable within the generic percpu code.

Reported-and-bisected-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Tested-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Fixes: 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap like events do")
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
 include/asm-generic/percpu.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index 40e887068da21..0504ef8f3aa31 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -118,9 +118,9 @@ do {									\
 #define this_cpu_generic_read(pcp)					\
 ({									\
 	typeof(pcp) __ret;						\
-	preempt_disable();						\
+	preempt_disable_notrace();					\
 	__ret = raw_cpu_generic_read(pcp);				\
-	preempt_enable();						\
+	preempt_enable_notrace();					\
 	__ret;								\
 })
 
-- 
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