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

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Message-ID: <6f362a9d-a87e-4061-bf41-14810e432333@amd.com>
Date: Wed, 13 Nov 2024 22:30:28 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: "Uladzislau Rezki (Sony)" <urezki@...il.com>,
 Frederic Weisbecker <frederic@...nel.org>
Cc: "Paul E . McKenney" <paulmck@...nel.org>, RCU <rcu@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>, Boqun Feng <boqun.feng@...il.com>,
 Joel Fernandes <joel@...lfernandes.org>,
 Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
 Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: [PATCH v2 1/2] rcuscale: Do a proper cleanup if
 kfree_scale_init() fails

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@...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>
> ---

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

- Neeraj