Re: [PATCH tip/core/rcu 03/28] locktorture: Track time of last ->writeunlock()

[Davidlohr Bueso]

On Thu, 05 Nov 2020, paulmck@xxxxxxxxxx wrote:

> From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
>
> This commit adds a last_lock_release variable that tracks the time of
> the last ->writeunlock() call, which allows easier diagnosing of lock
> hangs when using a kernel debugger.

This makes sense to have.

Acked-by: Davidlohr Bueso <dbueso@xxxxxxx>

> Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> ---
> kernel/locking/locktorture.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
> index 62d215b..316531d 100644
> --- a/kernel/locking/locktorture.c
> +++ b/kernel/locking/locktorture.c
> @@ -60,6 +60,7 @@ static struct task_struct **reader_tasks;
>
> static bool lock_is_write_held;
> static bool lock_is_read_held;
> +static unsigned long last_lock_release;
>
> struct lock_stress_stats {
> 	long n_lock_fail;
> @@ -632,6 +633,7 @@ static int lock_torture_writer(void *arg)
> 		lwsp->n_lock_acquired++;
> 		cxt.cur_ops->write_delay(&rand);
> 		lock_is_write_held = false;
> +		WRITE_ONCE(last_lock_release, jiffies);
> 		cxt.cur_ops->writeunlock();
>
> 		stutter_wait("lock_torture_writer");
> --
> 2.9.5