Re: [PATCH] srcutiny: Add lockdep and early-boot checks to synchronize_srcu_atomic()

[Bradley Morgan <brads@mainlining.org>]

On 11 September 2026 17:09:13 BST, Kunwu Chan <kunwu.chan@gmail.com> wrote:
>Add the RCU_LOCKDEP_WARN and early-boot check that the Tree version
>gained, srcu_lock_sync() was already present.
>
>Suggested-by: Zqiang <qiang.zhang@linux.dev>

Ok.

Reviewed-by: Bradley Morgan <brads@mainlining.org>


>Signed-off-by: Kunwu Chan <kunwu.chan@gmail.com>
>---
> kernel/rcu/srcutiny.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
>diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
>index 99f8bfd98b04..76411562366f 100644
>--- a/kernel/rcu/srcutiny.c
>+++ b/kernel/rcu/srcutiny.c
>@@ -361,6 +361,12 @@ void synchronize_srcu_atomic(struct srcu_struct *ssp)
> 
> 	srcu_lock_sync(&ssp->dep_map);
> 
>+	RCU_LOCKDEP_WARN(lockdep_is_held(ssp),
>+			 "Illegal synchronize_srcu_atomic() in same-type SRCU read-side critical section");
>+
>+	if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
>+		return;
>+

Wow!

> 	if (IS_ENABLED(CONFIG_PREEMPTION))
> 		synchronize_rcu(); // Needed for RCU Tasks Trace to imply RCU grace period.
> 				   // And in Tiny RCU, it is near zero cost and doesn't block.
>

--- Thanks!
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@grrlz.net/