From: Zong Li <zong.li@xxxxxxxxxx>
commit 4230e2deaa484b385aa01d598b2aea8e7f2660a6 upstream.
Some architectures assume that the stopped CPUs don't make function calls
to traceable functions when they are in the stopped state. See also commit
cb9d7fd51d9f ("watchdog: Mark watchdog touch functions as notrace").
Violating this assumption causes kernel crashes when switching tracer on
RISC-V.
Mark rcu_momentary_dyntick_idle() and stop_machine_yield() notrace to
prevent this.
Fixes: 4ecf0a43e729 ("processor: get rid of cpu_relax_yield")
Fixes: 366237e7b083 ("stop_machine: Provide RCU quiescent state in multi_cpu_stop()")
Signed-off-by: Zong Li <zong.li@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Atish Patra <atish.patra@xxxxxxx>
Tested-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Acked-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20201021073839.43935-1-zong.li@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 2 +-
kernel/stop_machine.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -416,7 +416,7 @@ bool rcu_eqs_special_set(int cpu)
*
* The caller must have disabled interrupts and must not be idle.
*/
-void rcu_momentary_dyntick_idle(void)
+notrace void rcu_momentary_dyntick_idle(void)
{
int special;
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -178,7 +178,7 @@ static void ack_state(struct multi_stop_
set_state(msdata, msdata->state + 1);
}
-void __weak stop_machine_yield(const struct cpumask *cpumask)
+notrace void __weak stop_machine_yield(const struct cpumask *cpumask)
{
cpu_relax();
}
