linux-kernel - Re: [PATCH] kernel/watchdog: fix warning -Wunused-variable for watchdog_allowed

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Message-ID: <20200820113056.GG4353@alley>
Date:   Thu, 20 Aug 2020 13:30:56 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Balamuruhan S <bala24@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de,
        peterz@...radead.org, Jisheng.Zhang@...aptics.com, rdna@...com,
        viro@...iv.linux.org.uk, gpiccoli@...onical.com,
        naveen.n.rao@...ux.vnet.ibm.com, ravi.bangoria@...ux.ibm.com,
        sandipan@...ux.ibm.com, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] kernel/watchdog: fix warning -Wunused-variable for
 watchdog_allowed_mask in ppc64

On Fri 2020-08-14 19:03:30, Balamuruhan S wrote:
> In ppc64 config if `CONFIG_SOFTLOCKUP_DETECTOR` is not set then it
> warns for unused declaration of `watchdog_allowed_mask` while building,
> move the declaration inside ifdef later in the code.
> 
> ```
> kernel/watchdog.c:47:23: warning: ‘watchdog_allowed_mask’ defined but not used [-Wunused-variable]
>  static struct cpumask watchdog_allowed_mask __read_mostly;
> ```
> 
> Signed-off-by: Balamuruhan S <bala24@...ux.ibm.com>
> ---
>  kernel/watchdog.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 5abb5b22ad13..33c9b8a3d51b 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -44,7 +44,6 @@ int __read_mostly soft_watchdog_user_enabled = 1;
>  int __read_mostly watchdog_thresh = 10;
>  static int __read_mostly nmi_watchdog_available;
>  
> -static struct cpumask watchdog_allowed_mask __read_mostly;
>  
>  struct cpumask watchdog_cpumask __read_mostly;
>  unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
> @@ -166,6 +165,7 @@ int __read_mostly sysctl_softlockup_all_cpu_backtrace;
>  unsigned int __read_mostly softlockup_panic =
>  			CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
>  
> +static struct cpumask watchdog_allowed_mask __read_mostly;

I could confirm that the variable is used only in code that is built
when CONFIG_SOFTLOCKUP_DETECTOR is enabled.

Note that the problem can't be seen on x86. There the softlockup
detector is enforced together with hardloclup detector via
via HARDLOCKUP_DETECTOR_PERF.

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr