cpuidle/rcu: Making arch_cpu_idle and rcu_idle_exit noinstr

Making arch_cpu_idle and rcu_idle_exit noinstr. Both functions run in rcu 'not watching' context and if there's tracer attached to them, which uses rcu (e.g. kprobe multi interface) it will hit RCU warning like: [ 3.017540] WARNING: suspicious RCU usage ... [ 3.018363] kprobe_multi_link_handler+0x68/0x1c0 [ 3.018364] ? kprobe_multi_link_handler+0x3e/0x1c0 [ 3.018366] ? arch_cpu_idle_dead+0x10/0x10 [ 3.018367] ? arch_cpu_idle_dead+0x10/0x10 [ 3.018371] fprobe_handler.part.0+0xab/0x150 [ 3.018374] 0xffffffffa00080c8 [ 3.018393] ? arch_cpu_idle+0x5/0x10 [ 3.018398] arch_cpu_idle+0x5/0x10 [ 3.018399] default_idle_call+0x59/0x90 [ 3.018401] do_idle+0x1c3/0x1d0 The call path is following: default_idle_call rcu_idle_enter arch_cpu_idle rcu_idle_exit The arch_cpu_idle and rcu_idle_exit are the only ones from above path that are traceble and cause this problem on my setup. Signed-off-by: Jiri Olsa <jolsa@kernel.org>
intel-lab-lkp · May 15, 2022 · 0b6fee3 · 0b6fee3
1 parent 418fbe8
commit 0b6fee3
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Showing 2 changed files with 2 additions and 2 deletions.
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
@@ -720,7 +720,7 @@ void arch_cpu_idle_dead(void)
 /*
  * Called from the generic idle code.
  */
-void arch_cpu_idle(void)
+void noinstr arch_cpu_idle(void)
 {
 	x86_idle();
 }

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
@@ -896,7 +896,7 @@ static void noinstr rcu_eqs_exit(bool user)
  * If you add or remove a call to rcu_idle_exit(), be sure to test with
  * CONFIG_RCU_EQS_DEBUG=y.
  */
-void rcu_idle_exit(void)
+void noinstr rcu_idle_exit(void)
 {
 	unsigned long flags;