linux-kernel - Re: [PATCH] rcutorture: Make rcutorture support print rcu-tasks gp state

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Message-ID: <40a4b0f3-b850-4d73-b514-ce5149abb465@paulmck-laptop>
Date: Sat, 16 Mar 2024 22:11:59 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Zqiang <qiang.zhang1211@...il.com>
Cc: frederic@...nel.org, neeraj.upadhyay@...nel.org, joel@...lfernandes.org,
	rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcutorture: Make rcutorture support print rcu-tasks gp
 state

On Tue, Mar 12, 2024 at 03:23:57PM +0800, Zqiang wrote:
> This commit make rcu-tasks related rcutorture test support rcu-tasks
> gp state printing when the writer stall occurs or the at the end of
> rcutorture test.
> 
> The test is as follows:
> [ 3872.548702] tasks-tracing:  Start-test grace-period state: g4560 f0x0
> [ 4332.661283] tasks-tracing:  End-test grace-period state: g41540 f0x0 total-gps=36980
> 
> [ 4401.381138] tasks:  Start-test grace-period state: g8 f0x0
> [ 4565.619354] tasks:  End-test grace-period state: g1732 f0x0 total-gps=1724
> 
> [ 4589.006917] tasks-rude:  Start-test grace-period state: g8 f0x0
> [ 5059.379321] tasks-rude:  End-test grace-period state: g8508 f0x0 total-gps=8500
> 
> Signed-off-by: Zqiang <qiang.zhang1211@...il.com>

Again, good eyes, and that fix would work.  But wouldn't it make more
sense to create a new cur_ops function pointer for these functions?
That might allow getting rid of the *_FLAVOR checks and values, plus
simplify the code a bit.  To make the function signatures work out,
there would need to be an intermediate SRCU function to supply the right
rcu_struct pointer.

This would shorten and simplify the code a bit.

Or is there some reason that this won't work?

Why didn't I do that to start with?  Well, the various RCU flavors
appeared one at a time over some years...  ;-)

							Thanx, Paul

> ---
>  kernel/rcu/rcu.h        |  8 ++++++++
>  kernel/rcu/rcutorture.c |  3 +++
>  kernel/rcu/tasks.h      | 25 +++++++++++++++++++++++++
>  3 files changed, 36 insertions(+)
> 
> diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
> index 86fce206560e..3353e3697645 100644
> --- a/kernel/rcu/rcu.h
> +++ b/kernel/rcu/rcu.h
> @@ -556,6 +556,14 @@ static inline unsigned long rcu_get_jiffies_lazy_flush(void) { return 0; }
>  static inline void rcu_set_jiffies_lazy_flush(unsigned long j) { }
>  #endif
>  
> +#ifdef CONFIG_TASKS_RCU_GENERIC
> +void rcutaskstorture_get_gp_data(enum rcutorture_type test_type, int *flags,
> +				unsigned long *gp_seq);
> +#else
> +static inline void rcutaskstorture_get_gp_data(enum rcutorture_type test_type, int *flags,
> +				unsigned long *gp_seq) { }
> +#endif
> +
>  #if defined(CONFIG_TREE_RCU)
>  void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
>  			    unsigned long *gp_seq);
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index dd7d5ba45740..91c03f37fd97 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -2267,6 +2267,7 @@ rcu_torture_stats_print(void)
>  				       &flags, &gp_seq);
>  		srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
>  					&flags, &gp_seq);
> +		rcutaskstorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
>  		wtp = READ_ONCE(writer_task);
>  		pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#x cpu %d\n",
>  			 rcu_torture_writer_state_getname(),
> @@ -3391,6 +3392,7 @@ rcu_torture_cleanup(void)
>  
>  	rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
>  	srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
> +	rcutaskstorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
>  	pr_alert("%s:  End-test grace-period state: g%ld f%#x total-gps=%ld\n",
>  		 cur_ops->name, (long)gp_seq, flags,
>  		 rcutorture_seq_diff(gp_seq, start_gp_seq));
> @@ -3763,6 +3765,7 @@ rcu_torture_init(void)
>  	rcu_torture_print_module_parms(cur_ops, "Start of test");
>  	rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
>  	srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
> +	rcutaskstorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
>  	start_gp_seq = gp_seq;
>  	pr_alert("%s:  Start-test grace-period state: g%ld f%#x\n",
>  		 cur_ops->name, (long)gp_seq, flags);
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index e83adcdb49b5..b1254cf3c210 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -2149,6 +2149,31 @@ late_initcall(rcu_tasks_verify_schedule_work);
>  static void rcu_tasks_initiate_self_tests(void) { }
>  #endif /* #else #ifdef CONFIG_PROVE_RCU */
>  
> +void rcutaskstorture_get_gp_data(enum rcutorture_type test_type, int *flags,
> +				unsigned long *gp_seq)
> +{
> +	switch (test_type) {
> +	case RCU_TASKS_FLAVOR:
> +#ifdef CONFIG_TASKS_RCU
> +		*gp_seq = rcu_seq_current(&rcu_tasks.tasks_gp_seq);
> +#endif
> +		break;
> +	case RCU_TASKS_RUDE_FLAVOR:
> +#ifdef CONFIG_TASKS_RUDE_RCU
> +		*gp_seq = rcu_seq_current(&rcu_tasks_rude.tasks_gp_seq);
> +#endif
> +		break;
> +	case RCU_TASKS_TRACING_FLAVOR:
> +#ifdef CONFIG_TASKS_TRACE_RCU
> +		*gp_seq = rcu_seq_current(&rcu_tasks_trace.tasks_gp_seq);
> +#endif
> +		break;
> +	default:
> +		break;
> +	}
> +}
> +EXPORT_SYMBOL_GPL(rcutaskstorture_get_gp_data);
> +
>  void __init tasks_cblist_init_generic(void)
>  {
>  	lockdep_assert_irqs_disabled();
> -- 
> 2.17.1
>