Re: [PATCH v4 1/4] locktorture: Add nested_[un]lock() hooks and nlocks parameter

[Paul E. McKenney]

On Tue, Feb 21, 2023 at 07:02:35PM +0000, John Stultz wrote:
> In order to extend locktorture to support lock nesting, add
> nested_lock() and nested_unlock() hooks to the torture ops.
> 
> These take a 32bit lockset mask which is generated at random,
> so some number of locks will be taken before the main lock is
> taken and released afterwards.
> 
> Additionally, add nested_locks module parameter to allow
> specifying the number of nested locks to be used.
> 
> This has been helpful to uncover issues in the proxy-exec
> series development.
> 
> This was inspired by locktorture extensions originally implemented
> by Connor O'Brien, for stress testing the proxy-execution series:
>   https://lore.kernel.org/lkml/20221003214501.2050087-12-connoro@xxxxxxxxxx/
> 
> Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
> Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
> Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
> Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
> Cc: kernel-team@xxxxxxxxxxx
> Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> Co-developed-by: Connor O'Brien <connoro@xxxxxxxxxx>
> Signed-off-by: Connor O'Brien <connoro@xxxxxxxxxx>
> Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>

I queued this series in place of its precedessor, thank you for the
update!

Given what I know now, I will set this up for the v6.4 merge window.

							Thanx, Paul

> ---
> v3:
> * Minor commit message tweaks and naming changes
>   suggested by Davidlohr Bueso
> v4:
> * Add co-developed tag
> ---
>  kernel/locking/locktorture.c | 23 +++++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
> index 9c2fb613a55d..6fe046594868 100644
> --- a/kernel/locking/locktorture.c
> +++ b/kernel/locking/locktorture.c
> @@ -48,6 +48,9 @@ torture_param(int, stat_interval, 60,
>  torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
>  torture_param(int, verbose, 1,
>  	     "Enable verbose debugging printk()s");
> +torture_param(int, nested_locks, 0, "Number of nested locks (max = 8)");
> +/* Going much higher trips "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!" errors */
> +#define MAX_NESTED_LOCKS 8
>  
>  static char *torture_type = "spin_lock";
>  module_param(torture_type, charp, 0444);
> @@ -76,10 +79,12 @@ static void lock_torture_cleanup(void);
>  struct lock_torture_ops {
>  	void (*init)(void);
>  	void (*exit)(void);
> +	int (*nested_lock)(int tid, u32 lockset);
>  	int (*writelock)(int tid);
>  	void (*write_delay)(struct torture_random_state *trsp);
>  	void (*task_boost)(struct torture_random_state *trsp);
>  	void (*writeunlock)(int tid);
> +	void (*nested_unlock)(int tid, u32 lockset);
>  	int (*readlock)(int tid);
>  	void (*read_delay)(struct torture_random_state *trsp);
>  	void (*readunlock)(int tid);
> @@ -669,6 +674,7 @@ static int lock_torture_writer(void *arg)
>  	struct lock_stress_stats *lwsp = arg;
>  	int tid = lwsp - cxt.lwsa;
>  	DEFINE_TORTURE_RANDOM(rand);
> +	u32 lockset_mask;
>  
>  	VERBOSE_TOROUT_STRING("lock_torture_writer task started");
>  	set_user_nice(current, MAX_NICE);
> @@ -677,7 +683,10 @@ static int lock_torture_writer(void *arg)
>  		if ((torture_random(&rand) & 0xfffff) == 0)
>  			schedule_timeout_uninterruptible(1);
>  
> +		lockset_mask = torture_random(&rand);
>  		cxt.cur_ops->task_boost(&rand);
> +		if (cxt.cur_ops->nested_lock)
> +			cxt.cur_ops->nested_lock(tid, lockset_mask);
>  		cxt.cur_ops->writelock(tid);
>  		if (WARN_ON_ONCE(lock_is_write_held))
>  			lwsp->n_lock_fail++;
> @@ -690,6 +699,8 @@ static int lock_torture_writer(void *arg)
>  		lock_is_write_held = false;
>  		WRITE_ONCE(last_lock_release, jiffies);
>  		cxt.cur_ops->writeunlock(tid);
> +		if (cxt.cur_ops->nested_unlock)
> +			cxt.cur_ops->nested_unlock(tid, lockset_mask);
>  
>  		stutter_wait("lock_torture_writer");
>  	} while (!torture_must_stop());
> @@ -830,11 +841,11 @@ lock_torture_print_module_parms(struct lock_torture_ops *cur_ops,
>  				const char *tag)
>  {
>  	pr_alert("%s" TORTURE_FLAG
> -		 "--- %s%s: nwriters_stress=%d nreaders_stress=%d stat_interval=%d verbose=%d shuffle_interval=%d stutter=%d shutdown_secs=%d onoff_interval=%d onoff_holdoff=%d\n",
> +		 "--- %s%s: nwriters_stress=%d nreaders_stress=%d nested_locks=%d stat_interval=%d verbose=%d shuffle_interval=%d stutter=%d shutdown_secs=%d onoff_interval=%d onoff_holdoff=%d\n",
>  		 torture_type, tag, cxt.debug_lock ? " [debug]": "",
> -		 cxt.nrealwriters_stress, cxt.nrealreaders_stress, stat_interval,
> -		 verbose, shuffle_interval, stutter, shutdown_secs,
> -		 onoff_interval, onoff_holdoff);
> +		 cxt.nrealwriters_stress, cxt.nrealreaders_stress,
> +		 nested_locks, stat_interval, verbose, shuffle_interval,
> +		 stutter, shutdown_secs, onoff_interval, onoff_holdoff);
>  }
>  
>  static void lock_torture_cleanup(void)
> @@ -1053,6 +1064,10 @@ static int __init lock_torture_init(void)
>  		}
>  	}
>  
> +	/* cap nested_locks to MAX_NESTED_LOCKS */
> +	if (nested_locks > MAX_NESTED_LOCKS)
> +		nested_locks = MAX_NESTED_LOCKS;
> +
>  	if (cxt.cur_ops->readlock) {
>  		reader_tasks = kcalloc(cxt.nrealreaders_stress,
>  				       sizeof(reader_tasks[0]),
> -- 
> 2.39.2.637.g21b0678d19-goog
>