On 21/10/2020 08:38, Zong Li wrote: > 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@xxxxxxxxxx> > --- > 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(); > } > Apologies for taking so long to reply, I needed to test this on several devices. This not only fixes the ftrace issue I see on RISC-V but also a ftrace hang issue on ARM64 in 5.8 too. Tested-by: Colin Ian King <colin.king@xxxxxxxxxxxxx> Many thanks!