linux-kernel - [PATCH] stop_machine: Mark functions as notrace

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Date:   Wed, 21 Oct 2020 15:38:39 +0800
From:   Zong Li <zong.li@...ive.com>
To:     paulmck@...nel.org, josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        joel@...lfernandes.org, vincent.whitchurch@...s.com,
        tglx@...utronix.de, paul.walmsley@...ive.com,
        palmerdabbelt@...gle.com, guoren@...nel.org, atishp@...shpatra.org,
        mhiramat@...nel.org, greentime.hu@...ive.com,
        colin.king@...onical.com, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Cc:     Zong Li <zong.li@...ive.com>
Subject: [PATCH] stop_machine: Mark functions as notrace

Like the commit cb9d7fd51d9f ("watchdog: Mark watchdog touch 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. For example, it causes unexpected kernel crashed when switching
tracer on RISC-V.

The following patches added calls to these two functions, fix it by
adding the notrace annotations.

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@...ive.com>
---
 kernel/rcu/tree.c     | 2 +-
 kernel/stop_machine.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 06895ef85d69..2a52f42f64b6 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -409,7 +409,7 @@ 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;
 
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();
 }
-- 
2.28.0