linux-kernel - [PATCH v2 1/2] rcuscale: Do a proper cleanup if kfree_scale

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Message-Id: <20241113110009.65256-1-urezki@gmail.com>
Date: Wed, 13 Nov 2024 12:00:08 +0100
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
To: Frederic Weisbecker <frederic@...nel.org>
Cc: "Paul E . McKenney" <paulmck@...nel.org>,
	RCU <rcu@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Neeraj upadhyay <Neeraj.Upadhyay@....com>,
	Boqun Feng <boqun.feng@...il.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
	Dan Carpenter <dan.carpenter@...aro.org>
Subject: [PATCH v2 1/2] rcuscale: Do a proper cleanup if kfree_scale_init() fails

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@...nel.org>
Reported-by: Dan Carpenter <dan.carpenter@...aro.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@...il.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