The following commit has been merged into the smp/urgent branch of tip:
Commit-ID: 4230e2deaa484b385aa01d598b2aea8e7f2660a6 Gitweb: https://git.kernel.org/tip/4230e2deaa484b385aa01d598b2aea8e7f2660a6 Author: Zong Li zong.li@sifive.com AuthorDate: Wed, 21 Oct 2020 15:38:39 +08:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Mon, 26 Oct 2020 12:12:27 +01:00
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/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 06895ef..2a52f42 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 865bb02..890b79c 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(); }