From 4230e2deaa484b385aa01d598b2aea8e7f2660a6 Mon Sep 17 00:00:00 2001
From: Zong Li <zong.li@sifive.com>
Date: Wed, 21 Oct 2020 15:38:39 +0800
Subject: stop_machine, rcu: Mark functions as notrace
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@sifive.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Atish Patra <atish.patra@wdc.com>
Tested-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20201021073839.43935-1-zong.li@sifive.com
---
kernel/stop_machine.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
(limited to 'kernel/stop_machine.c')
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 865bb0228ab6..890b79cf0e7c 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -178,7 +178,7 @@ static void ack_state(struct multi_stop_data *msdata)
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();
}
--
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