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 cb9d7fd ("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: 4ecf0a4 ("processor: get rid of cpu_relax_yield") Fixes: 366237e ("stop_machine: Provide RCU quiescent state in multi_cpu_stop()") Signed-off-by: Zong Li <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Tested-by: Atish Patra <[email protected]> Tested-by: Colin Ian King <[email protected]> Acked-by: Steven Rostedt (VMware) <[email protected]> Acked-by: Paul E. McKenney <[email protected]> Cc: [email protected] Link: https://lore.kernel.org/r/[email protected]
josf · Oct 26, 2020 · 4230e2d · 4230e2d
1 parent 3650b22
commit 4230e2d
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Showing 2 changed files with 2 additions and 2 deletions.
diff --git 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
@@ -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();
 }