Re: [PATCH rcu 06/11] rcuscale: Provide clear error when async specified without primitives
From: Neeraj Upadhyay
Date: Wed Aug 14 2024 - 08:49:28 EST
On Thu, Aug 01, 2024 at 05:43:03PM -0700, Paul E. McKenney wrote:
> Currently, if the rcuscale module's async module parameter is specified
> for RCU implementations that do not have sync primitives such as
> call_rcu(), there will be a series of splats due to calls to a NULL
> pointer. This commit therefore warns of this situation, but switches
> to non-async testing.
>
I have changed this to below here [1]. Please let me know if I got it
wrong.
Currently, if the rcuscale module's async module parameter is specified
for RCU implementations that do not have async primitives such as
RCU Tasks Rude, there will be a series of splats due to calls to a NULL
pointer. This commit therefore warns of this situation, but switches to
non-async testing.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/neeraj.upadhyay/linux-rcu.git/commit/?h=next.14.08.24b&id=22d36840adbcab8fd826a7ca827fd60b708f03de
- Neeraj
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> ---
> kernel/rcu/rcuscale.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
> index 933014b381ec0..315ced63ec105 100644
> --- a/kernel/rcu/rcuscale.c
> +++ b/kernel/rcu/rcuscale.c
> @@ -525,7 +525,7 @@ rcu_scale_writer(void *arg)
> schedule_timeout_idle(torture_random(&tr) % writer_holdoff_jiffies + 1);
> wdp = &wdpp[i];
> *wdp = ktime_get_mono_fast_ns();
> - if (gp_async) {
> + if (gp_async && !WARN_ON_ONCE(!cur_ops->async)) {
> retry:
> if (!rhp)
> rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
> @@ -597,7 +597,7 @@ rcu_scale_writer(void *arg)
> i++;
> rcu_scale_wait_shutdown();
> } while (!torture_must_stop());
> - if (gp_async) {
> + if (gp_async && cur_ops->async) {
> cur_ops->gp_barrier();
> }
> writer_n_durations[me] = i_max + 1;
> --
> 2.40.1
>