On Mon, Sep 07, 2026 at 03:58:27PM +0800, Kunwu Chan wrote:
> From: Kunwu Chan <[email protected]>
>
> The atomic-SRCU path in srcu_barrier() sleeps for 100 milliseconds just
> in case there are callbacks to wait for. But call_srcu() refuses
> atomic SRCU with a WARN_ON_ONCE() before reaching the deferred-enqueue
> path, so there can be no callbacks, deferred or otherwise.
>
> Drop the sleep.
>
> Signed-off-by: Kunwu Chan <[email protected]>
Good catch! As you say, now that call_srcu() leaks callbacks that are
for atomic srcu_struct structures, there really cannot be any callbacks.
Queued for further review and testing, thank you!
Thanx, Paul
> ---
> kernel/rcu/srcutree.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> index c19f59725706..a93bf803e2f7 100644
> --- a/kernel/rcu/srcutree.c
> +++ b/kernel/rcu/srcutree.c
> @@ -1895,12 +1895,9 @@ void srcu_barrier(struct srcu_struct *ssp)
> unsigned long s;
>
> check_init_srcu_struct(ssp, false);
> - if (WARN_ON_ONCE(ssp->srcu_reader_flavor == SRCU_READ_FLAVOR_ATOMIC)) {
> - // There shouldn't be any callbacks for atomic SRCU,
> - // but just in case.
> - schedule_timeout_uninterruptible(HZ/10);
> + // Atomic SRCU has no callbacks, so there is nothing to wait on.
> + if (WARN_ON_ONCE(ssp->srcu_reader_flavor == SRCU_READ_FLAVOR_ATOMIC))
> return;
> - }
>
> /*
> * Register any deferred callbacks before snapshotting the sequence.
> The
> --
> 2.43.0
>
