linux-kernel - RE: [RFC][PATCH 17/18 v2] ftrace/cpuidle/x86: Mark functions that are RCU unsafe

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Message-ID: <niy9r1aodpxs3r912ut902gi.1377947166977@email.android.com>
Date:	Sat, 31 Aug 2013 11:07:29 +0000
From:	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>
To:	"rostedt@...dmis.org" <rostedt@...dmis.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"mingo@...nel.org" <mingo@...nel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	"jolsa@...hat.com" <jolsa@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>
Subject: RE: [RFC][PATCH 17/18 v2] ftrace/cpuidle/x86: Mark functions that
 are RCU unsafe

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>




Sent from a tablet, I apologize for formatting issues.

Steven Rostedt <rostedt@...dmis.org> wrote:
From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>

Some callbacks of the function tracer use rcu_read_lock(). This means that
there's places that can not be traced because RCU is not tracking the CPU
for various reasons (like NO_HZ_FULL and coming back from userspace).

Thes functions need to be marked so that callbacks that use RCU do not
trace them.

Cc: H. Peter Anvin <hpa@...or.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 arch/x86/kernel/process.c |    2 ++
 drivers/cpuidle/cpuidle.c |    2 ++
 kernel/cpu/idle.c         |    2 ++
 3 files changed, 6 insertions(+)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 83369e5..18739cd 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -17,6 +17,7 @@
 #include <linux/stackprotector.h>
 #include <linux/tick.h>
 #include <linux/cpuidle.h>
+#include <linux/ftrace.h>
 #include <trace/events/power.h>
 #include <linux/hw_breakpoint.h>
 #include <asm/cpu.h>
@@ -316,6 +317,7 @@ void default_idle(void)
 #ifdef CONFIG_APM_MODULE
 EXPORT_SYMBOL(default_idle);
 #endif
+FTRACE_UNSAFE_RCU(default_idle);

 #ifdef CONFIG_XEN
 bool xen_set_default_idle(void)
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index fdc432f..9515457 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -19,6 +19,7 @@
 #include <linux/ktime.h>
 #include <linux/hrtimer.h>
 #include <linux/module.h>
+#include <linux/ftrace.h>
 #include <trace/events/power.h>

 #include "cpuidle.h"
@@ -168,6 +169,7 @@ int cpuidle_idle_call(void)

         return 0;
 }
+FTRACE_UNSAFE_RCU(cpuidle_idle_call);

 /**
  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c
index e695c0a..d9d290f 100644
--- a/kernel/cpu/idle.c
+++ b/kernel/cpu/idle.c
@@ -5,6 +5,7 @@
 #include <linux/cpu.h>
 #include <linux/tick.h>
 #include <linux/mm.h>
+#include <linux/ftrace.h>
 #include <linux/stackprotector.h>

 #include <asm/tlb.h>
@@ -61,6 +62,7 @@ void __weak arch_cpu_idle(void)
         cpu_idle_force_poll = 1;
         local_irq_enable();
 }
+FTRACE_UNSAFE_RCU(arch_cpu_idle);

 /*
  * Generic idle loop implementation
--
1.7.10.4


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