linux-kernel - [PATCH 2/2] kernel: sched: fix preempt_disable_ip recodring for preempt

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Message-Id: <1455232867-29059-2-git-send-email-bigeasy@linutronix.de>
Date:	Fri, 12 Feb 2016 00:21:07 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 2/2] kernel: sched: fix preempt_disable_ip recodring for preempt_disable()

The preempt_disable() invokes preempt_count_add() which saves the caller
in ->preempt_disable_ip. It uses CALLER_ADDR1 which does not look for
its caller but for the parent of the caller. Which means we get the correct
caller for something like spin_lock() unless the architectures inlines
those invocations. It is always wrong for preempt_disable() or
local_bh_disable().

This patch makes the function get_parent_ip() which tries
CALLER_ADDR0,1,2 if the former is a locking function.
This seems to record the preempt_disable() caller properly for
preempt_disable() itself as well as for get_cpu_var() or
local_bh_disable().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 include/linux/sched.h | 13 ++++++++++++-
 kernel/sched/core.c   | 14 ++------------
 kernel/softirq.c      |  4 ++--
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index a10494a94cc3..cd21fd41ba2a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -59,6 +59,7 @@ struct sched_param {
 #include <linux/gfp.h>
 #include <linux/magic.h>
 #include <linux/cgroup-defs.h>
+#include <linux/ftrace_caller.h>
 
 #include <asm/processor.h>
 
@@ -182,7 +183,17 @@ extern void update_cpu_load_nohz(int active);
 static inline void update_cpu_load_nohz(int active) { }
 #endif
 
-extern unsigned long get_parent_ip(unsigned long addr);
+static inline unsigned long get_parent_ip(void)
+{
+	unsigned long addr = CALLER_ADDR0;
+
+	if (!in_lock_functions(addr))
+		return addr;
+	addr = CALLER_ADDR1;
+	if (!in_lock_functions(addr))
+		return addr;
+	return CALLER_ADDR2;
+}
 
 extern void dump_cpu_task(int cpu);
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9503d590e5ef..12c2527f5957 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3010,16 +3010,6 @@ u64 scheduler_tick_max_deferment(void)
 }
 #endif
 
-notrace unsigned long get_parent_ip(unsigned long addr)
-{
-	if (in_lock_functions(addr)) {
-		addr = CALLER_ADDR2;
-		if (in_lock_functions(addr))
-			addr = CALLER_ADDR3;
-	}
-	return addr;
-}
-
 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
 				defined(CONFIG_PREEMPT_TRACER))
 
@@ -3041,7 +3031,7 @@ void preempt_count_add(int val)
 				PREEMPT_MASK - 10);
 #endif
 	if (preempt_count() == val) {
-		unsigned long ip = get_parent_ip(CALLER_ADDR1);
+		unsigned long ip = get_parent_ip();
 #ifdef CONFIG_DEBUG_PREEMPT
 		current->preempt_disable_ip = ip;
 #endif
@@ -3068,7 +3058,7 @@ void preempt_count_sub(int val)
 #endif
 
 	if (preempt_count() == val)
-		trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
+		trace_preempt_on(CALLER_ADDR0, get_parent_ip());
 	__preempt_count_sub(val);
 }
 EXPORT_SYMBOL(preempt_count_sub);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 479e4436f787..ec71033a87a2 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -116,9 +116,9 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
 
 	if (preempt_count() == cnt) {
 #ifdef CONFIG_DEBUG_PREEMPT
-		current->preempt_disable_ip = get_parent_ip(CALLER_ADDR1);
+		current->preempt_disable_ip = get_parent_ip();
 #endif
-		trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
+		trace_preempt_off(CALLER_ADDR0, get_parent_ip());
 	}
 }
 EXPORT_SYMBOL(__local_bh_disable_ip);
-- 
2.7.0