From ffc1b64ca3a9fae0af5278a212a443cb25578122 Mon Sep 17 00:00:00 2001 From: Zong Li Date: Wed, 21 Oct 2020 15:38:39 +0800 Subject: [PATCH] stop_machine, rcu: Mark functions as notrace 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 Signed-off-by: Thomas Gleixner Tested-by: Atish Patra Tested-by: Colin Ian King Acked-by: Steven Rostedt (VMware) Acked-by: Paul E. McKenney Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201021073839.43935-1-zong.li@sifive.com Signed-off-by: Greg Kroah-Hartman --- 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 388a2ad292bf4..c8f62e2d02761 100644 --- 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; diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 865bb0228ab66..890b79cf0e7c3 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(); }