Re: [PATCH rcu 11/15] rcutorture: Add reader_flavor parameter for SRCU readers

[Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>]

On 10/15/2024 9:41 PM, Paul E. McKenney wrote:
> This commit adds an rcutorture.reader_flavor parameter whose bits
> correspond to reader flavors.  For example, SRCU's readers are 0x1 for
> normal and 0x2 for NMI-safe.
> 
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Andrii Nakryiko <andrii@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Kent Overstreet <kent.overstreet@linux.dev>
> Cc: <bpf@vger.kernel.org>
> ---
>  .../admin-guide/kernel-parameters.txt         |  8 +++++
>  kernel/rcu/rcutorture.c                       | 30 ++++++++++++++-----
>  2 files changed, 30 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 1518343bbe223..52922727006fc 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5426,6 +5426,14 @@
>  			The delay, in seconds, between successive
>  			read-then-exit testing episodes.
>  
> +	rcutorture.reader_flavor= [KNL]
> +			A bit mask indicating which readers to use.
> +			If there is more than one bit set, the readers
> +			are entered from low-order bit up, and are
> +			exited in the opposite order.  For SRCU, the
> +			0x1 bit is normal readers and the 0x2 bit is
> +			for NMI-safe readers.
> +
>  	rcutorture.shuffle_interval= [KNL]
>  			Set task-shuffle interval (s).  Shuffling tasks
>  			allows some CPUs to go into dyntick-idle mode
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index f96ab98f8182f..405decec33677 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -111,6 +111,7 @@ torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disab
>  torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)");
>  torture_param(int, read_exit_delay, 13, "Delay between read-then-exit episodes (s)");
>  torture_param(int, read_exit_burst, 16, "# of read-then-exit bursts per episode, zero to disable");
> +torture_param(int, reader_flavor, 0x1, "Reader flavors to use, one per bit.");
>  torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
>  torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
>  torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
> @@ -644,10 +645,20 @@ static void srcu_get_gp_data(int *flags, unsigned long *gp_seq)
>  
>  static int srcu_torture_read_lock(void)
>  {
> -	if (cur_ops == &srcud_ops)
> -		return srcu_read_lock_nmisafe(srcu_ctlp);
> -	else
> -		return srcu_read_lock(srcu_ctlp);
> +	int idx;
> +	int ret = 0;
> +
> +	if ((reader_flavor & 0x1) || !(reader_flavor & 0x7)) {

Minor: Maybe use macros in place of 0x1, 0x2, 0x7 as a cleanup later.


- Neeraj

> +		idx = srcu_read_lock(srcu_ctlp);
> +		WARN_ON_ONCE(idx & ~0x1);
> +		ret += idx;
> +	}
> +	if (reader_flavor & 0x2) {
> +		idx = srcu_read_lock_nmisafe(srcu_ctlp);
> +		WARN_ON_ONCE(idx & ~0x1);
> +		ret += idx << 1;
> +	}
> +	return ret;
>  }
>