On Sun, Oct 04, 2026 at 12:17:19AM +0800, Kunwu Chan wrote:
> Add support for scaling atomic SRCU grace periods using
> srcu_read_lock_atomic()/srcu_read_unlock_atomic() and
> synchronize_srcu_atomic().
>
> Suggested-by: Paul E. McKenney <[email protected]>
> Signed-off-by: Kunwu Chan <[email protected]>
Queued for testing and further review, thank you!!!
Thanx, Paul
> ---
> Changes since v1:
> - Rename srcu_atomic_ctlp to srcua and reuse srcu_ctlp for
> SRCU operations, as suggested by Paul.
> - Reuse the existing SRCU cleanup and completed helpers by
> initializing srcu_ctlp in srcu_atomic_scale_init().
> - Add .stats using srcu_scale_stats().
> - Use "srcua" to match the existing "srcu" and "srcud" scale
> type names.
> - Use synchronize_srcu_atomic() for both normal and expedited
> scale tests.
>
> v1: https://lore.kernel.org/all/[email protected]/
> Tested with kvm.sh --torture rcuscale scale_type=srcua on x86_64 and
> arm64, alongside gp_exp=1 and PROVE_LOCKING=y: no warnings or lockdep
> splats.
> ---
> kernel/rcu/rcuscale.c | 41 ++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 40 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
> index 1097ec15879c..b172882824ac 100644
> --- a/kernel/rcu/rcuscale.c
> +++ b/kernel/rcu/rcuscale.c
> @@ -293,6 +293,44 @@ static struct rcu_scale_ops srcud_ops = {
> .name = "srcud"
> };
>
> +static struct srcu_struct srcua;
> +
> +static int srcu_scale_atomic_read_lock(void)
> +{
> + return srcu_read_lock_atomic(srcu_ctlp);
> +}
> +
> +static void srcu_scale_atomic_read_unlock(int idx)
> +{
> + srcu_read_unlock_atomic(srcu_ctlp, idx);
> +}
> +
> +static void srcu_scale_atomic_synchronize(void)
> +{
> + synchronize_srcu_atomic(srcu_ctlp);
> +}
> +
> +static void srcu_atomic_scale_init(void)
> +{
> + srcu_ctlp = &srcua;
> + init_srcu_struct_atomic(srcu_ctlp);
> +}
> +
> +static struct rcu_scale_ops srcua_ops = {
> + .ptype = SRCU_FLAVOR,
> + .init = srcu_atomic_scale_init,
> + .cleanup = srcu_sync_scale_cleanup,
> + .readlock = srcu_scale_atomic_read_lock,
> + .readunlock = srcu_scale_atomic_read_unlock,
> + .get_gp_seq = srcu_scale_completed,
> + .gp_diff = rcu_seq_diff,
> + .exp_completed = srcu_scale_completed,
> + .sync = srcu_scale_atomic_synchronize,
> + .exp_sync = srcu_scale_atomic_synchronize,
> + .stats = srcu_scale_stats,
> + .name = "srcua"
> +};
> +
> #ifdef CONFIG_TASKS_RCU
>
> /*
> @@ -1110,7 +1148,8 @@ rcu_scale_init(void)
> long i;
> long j;
> static struct rcu_scale_ops *scale_ops[] = {
> - &rcu_ops, &srcu_ops, &srcud_ops, TASKS_OPS TASKS_RUDE_OPS
> TASKS_TRACING_OPS
> + &rcu_ops, &srcu_ops, &srcua_ops, &srcud_ops,
> + TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
> };
>
> if (!torture_init_begin(scale_type, verbose))
>
> base-commit: d21906b0aa1e9573cdb5e7acaca44966b9d1dcd2
> --
> 2.43.0
>
