[PATCH v2 1/2] rcuscale: Do a proper cleanup if kfree_scale_init() fails

[PATCH v2 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.

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
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 | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 6d37596deb1f..d360fa44b234 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -890,13 +890,15 @@ 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;
+			firsterr = -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;
+			firsterr = -1;
+			goto unwind;
 		}
 	}
 
-- 
2.39.5

[PATCH v2 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.

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
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 d360fa44b234..0f3059b1b80d 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -889,14 +889,12 @@ 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);
 			firsterr = -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);
 			firsterr = -1;
 			goto unwind;
 		}
-- 
2.39.5

Re: [PATCH v2 1/2] rcuscale: Do a proper cleanup if kfree_scale_init() fails

[Neeraj Upadhyay]

On 11/13/2024 4:30 PM, Uladzislau Rezki (Sony) wrote:
> 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.
> 
> Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
> 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>
> ---

Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>


- Neeraj

Re: [PATCH v2 2/2] rcuscale: Remove redundant WARN_ON_ONCE() splat

[Neeraj Upadhyay]

On 11/13/2024 4:30 PM, 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.
> 
> Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> ---


Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>


- Neeraj