linux-kernel - [PATCH] watchdog: Mark watchdog touch functions as notrace

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Date:   Tue, 21 Aug 2018 17:25:07 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     mingo@...nel.org, tglx@...utronix.de
Cc:     oleg@...hat.com, linux-kernel@...r.kernel.org, tj@...nel.org,
        jiangshanlai@...il.com, Vincent Whitchurch <rabinv@...s.com>
Subject: [PATCH] watchdog: Mark watchdog touch functions as notrace

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

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 5470dce212c0..977918d5d350 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -261,7 +261,7 @@ 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
@@ -270,7 +270,7 @@ void touch_softlockup_watchdog_sched(void)
 	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());
diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index 1f7020d65d0a..71381168dede 100644
--- 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
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 78b192071ef7..5f78c6e41796 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5559,7 +5559,7 @@ static void wq_watchdog_timer_fn(struct timer_list *unused)
 	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;
-- 
2.11.0