linux-kernel - Re: [patch V2 25/29] lockup_detector: Implement init time detection of perf

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170913180237.whri2g7soahd3ljl@redhat.com>
Date:   Wed, 13 Sep 2017 14:02:37 -0400
From:   Don Zickus <dzickus@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Nicholas Piggin <npiggin@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Ulrich Obergfell <uobergfe@...hat.com>
Subject: Re: [patch V2 25/29] lockup_detector: Implement init time detection
 of perf

On Tue, Sep 12, 2017 at 09:37:19PM +0200, Thomas Gleixner wrote:
> Use the init time detection of the perf NMI watchdog to determine whether
> the perf NMI watchdog is functional. If not disable it permanentely. It
> won't come back magically at runtime.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Don Zickus <dzickus@...hat.com>
> Cc: Chris Metcalf <cmetcalf@...lanox.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Sebastian Siewior <bigeasy@...utronix.de>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: Ulrich Obergfell <uobergfe@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Link: http://lkml.kernel.org/r/20170831073054.997264122@linutronix.de
> 
> ---
>  kernel/watchdog.c |   13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -44,6 +44,7 @@ int __read_mostly watchdog_user_enabled
>  int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
>  int __read_mostly soft_watchdog_user_enabled = 1;
>  int __read_mostly watchdog_thresh = 10;
> +int __read_mostly nmi_watchdog_available;
>  
>  struct cpumask watchdog_allowed_mask __read_mostly;
>  static bool softlockup_threads_initialized __read_mostly;
> @@ -114,6 +115,12 @@ void __weak watchdog_nmi_disable(unsigne
>  	hardlockup_detector_perf_disable();
>  }
>  
> +/* Return 0, if a NMI watchdog is available. Error code otherwise */
> +int __weak __init void watchdog_nmi_probe(void)

^^^ compile error, can't have 'int' and 'void'.  Removing 'void' fixes it.

Cheers,
Don

> +{
> +	return hardlockup_detector_perf_init();
> +}
> +
>  /**
>   * watchdog_nmi_reconfigure - Optional function to reconfigure NMI watchdogs
>   * @run:	If false stop the watchdogs on all enabled CPUs
> @@ -145,7 +152,7 @@ static void lockup_detector_update_enabl
>  	watchdog_enabled = 0;
>  	if (!watchdog_user_enabled)
>  		return;
> -	if (nmi_watchdog_user_enabled)
> +	if (nmi_watchdog_available && nmi_watchdog_user_enabled)
>  		watchdog_enabled |= NMI_WATCHDOG_ENABLED;
>  	if (soft_watchdog_user_enabled)
>  		watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
> @@ -692,6 +699,8 @@ int proc_watchdog(struct ctl_table *tabl
>  int proc_nmi_watchdog(struct ctl_table *table, int write,
>  		      void __user *buffer, size_t *lenp, loff_t *ppos)
>  {
> +	if (!nmi_watchdog_available && write)
> +		return -ENOTSUPP;
>  	return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
>  				    table, write, buffer, lenp, ppos);
>  }
> @@ -764,5 +773,7 @@ void __init lockup_detector_init(void)
>  	cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
>  #endif
>  
> +	if (!watchdog_nmi_probe())
> +		nmi_watchdog_available = true;
>  	softlockup_init_threads();
>  }
> 
>