[PATCH 1/2] rcuscale: Do a proper cleanup if kfree_scale_init() fails

[PATCH 1/2] rcuscale: Do a proper cleanup if kfree_scale_init() fails

[Uladzislau Rezki (Sony)]

A static analyzer for C, Smatch, reports and triggers below
warnings:

   kernel/rcu/rcuscale.c:1215 rcu_scale_init()
   warn: inconsistent returns 'global &fullstop_mutex'.

The checker complains about, we do not unlock the "fullstop_mutex"
mutex, in case of hitting below error path:

<snip>
...
    if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start < 2 * HZ)) {
        pr_alert("ERROR: call_rcu() CBs are not being lazy as expected!\n");
        WARN_ON_ONCE(1);
        return -1;
        ^^^^^^^^^^
...
<snip>

it happens because "-1" is returned right away instead of
doing a proper unwinding.

Fix it by jumping to "unwind" label instead of returning -1.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/rcu/ZxfTrHuEGtgnOYWp@pc636/T/
Fixes: 084e04fff160 ("rcuscale: Add laziness and kfree tests")
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 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 6d37596deb1f..de7d511e6be4 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -890,13 +890,13 @@ kfree_scale_init(void)
 		if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start < 2 * HZ)) {
 			pr_alert("ERROR: call_rcu() CBs are not being lazy as expected!\n");
 			WARN_ON_ONCE(1);
-			return -1;
+			goto unwind;
 		}
 
 		if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start > 3 * HZ)) {
 			pr_alert("ERROR: call_rcu() CBs are being too lazy!\n");
 			WARN_ON_ONCE(1);
-			return -1;
+			goto unwind;
 		}
 	}
 
-- 
2.39.5

[PATCH 2/2] rcuscale: Remove redundant WARN_ON_ONCE() splat

[Uladzislau Rezki (Sony)]

There are two places where WARN_ON_ONCE() is called two times
in the error paths. One which is encapsulated into if() condition
and another one, which is unnecessary, is placed in the brackets.

Remove an extra WARN_ON_ONCE() splat which is in brackets.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 kernel/rcu/rcuscale.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index de7d511e6be4..1d8bb603c289 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -889,13 +889,11 @@ kfree_scale_init(void)
 
 		if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start < 2 * HZ)) {
 			pr_alert("ERROR: call_rcu() CBs are not being lazy as expected!\n");
-			WARN_ON_ONCE(1);
 			goto unwind;
 		}
 
 		if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start > 3 * HZ)) {
 			pr_alert("ERROR: call_rcu() CBs are being too lazy!\n");
-			WARN_ON_ONCE(1);
 			goto unwind;
 		}
 	}
-- 
2.39.5

Re: [PATCH 2/2] rcuscale: Remove redundant WARN_ON_ONCE() splat

[Paul E. McKenney]

On Thu, Oct 24, 2024 at 06:45:58PM +0200, Uladzislau Rezki (Sony) wrote:
> There are two places where WARN_ON_ONCE() is called two times
> in the error paths. One which is encapsulated into if() condition
> and another one, which is unnecessary, is placed in the brackets.
> 
> Remove an extra WARN_ON_ONCE() splat which is in brackets.
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

For both:

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>

> ---
>  kernel/rcu/rcuscale.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
> index de7d511e6be4..1d8bb603c289 100644
> --- a/kernel/rcu/rcuscale.c
> +++ b/kernel/rcu/rcuscale.c
> @@ -889,13 +889,11 @@ kfree_scale_init(void)
>  
>  		if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start < 2 * HZ)) {
>  			pr_alert("ERROR: call_rcu() CBs are not being lazy as expected!\n");
> -			WARN_ON_ONCE(1);
>  			goto unwind;
>  		}
>  
>  		if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start > 3 * HZ)) {
>  			pr_alert("ERROR: call_rcu() CBs are being too lazy!\n");
> -			WARN_ON_ONCE(1);
>  			goto unwind;
>  		}
>  	}
> -- 
> 2.39.5
> 

Re: [PATCH 2/2] rcuscale: Remove redundant WARN_ON_ONCE() splat

[Uladzislau Rezki]

On Thu, Oct 24, 2024 at 01:28:24PM -0700, Paul E. McKenney wrote:
> On Thu, Oct 24, 2024 at 06:45:58PM +0200, Uladzislau Rezki (Sony) wrote:
> > There are two places where WARN_ON_ONCE() is called two times
> > in the error paths. One which is encapsulated into if() condition
> > and another one, which is unnecessary, is placed in the brackets.
> > 
> > Remove an extra WARN_ON_ONCE() splat which is in brackets.
> > 
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> 
> For both:
> 
> Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
> 
Thank you :)

--
Uladzislau Rezki

Re: [PATCH 2/2] rcuscale: Remove redundant WARN_ON_ONCE() splat

[Frederic Weisbecker]

Le Thu, Oct 24, 2024 at 01:28:24PM -0700, Paul E. McKenney a écrit :
> On Thu, Oct 24, 2024 at 06:45:58PM +0200, Uladzislau Rezki (Sony) wrote:
> > There are two places where WARN_ON_ONCE() is called two times
> > in the error paths. One which is encapsulated into if() condition
> > and another one, which is unnecessary, is placed in the brackets.
> > 
> > Remove an extra WARN_ON_ONCE() splat which is in brackets.
> > 
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> 
> For both:
> 
> Reviewed-by: Paul E. McKenney <paulmck@kernel.org>

Both applied!

Thanks.