| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.9 380/391] stop_machine, rcu: Mark functions as notrace | Date | Tue, 3 Nov 2020 21:37:11 +0100 |
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From: Zong Li <zong.li@sifive.com>
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 <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 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- kernel/rcu/tree.c | 2 +- kernel/stop_machine.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
--- 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; --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -178,7 +178,7 @@ static void ack_state(struct multi_stop_ 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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