linux-kernel - [PATCH 4.18 120/123] watchdog: Mark watchdog touch functions as notrace

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Message-Id: <20180903165724.569740429@linuxfoundation.org>
Date:   Mon,  3 Sep 2018 18:57:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>, oleg@...hat.com,
        tj@...nel.org
Subject: [PATCH 4.18 120/123] watchdog: Mark watchdog touch functions as notrace

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vincent Whitchurch <vincent.whitchurch@...s.com>

commit cb9d7fd51d9fbb329d182423bd7b92d0f8cb0e01 upstream.

Some architectures need to use stop_machine() to patch functions for
ftrace, and the assumption is that the stopped CPUs do not make function
calls to traceable functions when they are in the stopped state.

Commit ce4f06dcbb5d ("stop_machine: Touch_nmi_watchdog() after
MULTI_STOP_PREPARE") added calls to the watchdog touch functions from
the stopped CPUs and those functions lack notrace annotations.  This
leads to crashes when enabling/disabling ftrace on ARM kernels built
with the Thumb-2 instruction set.

Fix it by adding the necessary notrace annotations.

Fixes: ce4f06dcbb5d ("stop_machine: Touch_nmi_watchdog() after MULTI_STOP_PREPARE")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: oleg@...hat.com
Cc: tj@...nel.org
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20180821152507.18313-1-vincent.whitchurch@axis.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/watchdog.c     |    4 ++--
 kernel/watchdog_hld.c |    2 +-
 kernel/workqueue.c    |    2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -266,7 +266,7 @@ static void __touch_watchdog(void)
  * entering idle state.  This should only be used for scheduler events.
  * Use touch_softlockup_watchdog() for everything else.
  */
-void touch_softlockup_watchdog_sched(void)
+notrace void touch_softlockup_watchdog_sched(void)
 {
 	/*
 	 * Preemption can be enabled.  It doesn't matter which CPU's timestamp
@@ -275,7 +275,7 @@ void touch_softlockup_watchdog_sched(voi
 	raw_cpu_write(watchdog_touch_ts, 0);
 }
 
-void touch_softlockup_watchdog(void)
+notrace void touch_softlockup_watchdog(void)
 {
 	touch_softlockup_watchdog_sched();
 	wq_watchdog_touch(raw_smp_processor_id());
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -29,7 +29,7 @@ static struct cpumask dead_events_mask;
 static unsigned long hardlockup_allcpu_dumped;
 static atomic_t watchdog_cpus = ATOMIC_INIT(0);
 
-void arch_touch_nmi_watchdog(void)
+notrace void arch_touch_nmi_watchdog(void)
 {
 	/*
 	 * Using __raw here because some code paths have
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5559,7 +5559,7 @@ static void wq_watchdog_timer_fn(struct
 	mod_timer(&wq_watchdog_timer, jiffies + thresh);
 }
 
-void wq_watchdog_touch(int cpu)
+notrace void wq_watchdog_touch(int cpu)
 {
 	if (cpu >= 0)
 		per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;