Re: Regression in kernel 4.13-rcX for 32-bit x86 system - bisected to commit fc8dffd379ca

[Larry Finger]

On 08/14/2017 02:21 AM, Thomas Gleixner wrote:
> On Mon, 14 Aug 2017, Larry Finger wrote:
>
> > My Del Latitude D600 (single 32-bit CPU) shows the following locking message
> > when booted:
> >
> > ============================================
> > WARNING: possible recursive locking detected
> > 4.12.0-rc2-00029-gfc8dffd #159 Not tainted
> > --------------------------------------------
> > systemd-udevd/153 is trying to acquire lock:
> >   (cpu_hotplug_lock.rw_sem){.+.+.+}, at: [<c030fc26>] stop_machine+0x16/0x30
> >
> > but task is already holding lock:
> >   (cpu_hotplug_lock.rw_sem){.+.+.+}, at: [<c0234353>] mtrr_add_page+0x83/0x470
>
> ....
>
> >   cpus_read_lock+0x48/0x90
> >   ? stop_machine+0x16/0x30
> >   stop_machine+0x16/0x30
> >   mtrr_add_page+0x18b/0x470
> >   mtrr_add+0x3e/0x70
>   
> > This problem was bisected to commit fc8dffd379ca ("cpu/hotplug: Convert
> > hotplug locking to percpu rwsem"). I am very confident in the correctness of
> > the bisection.
>
> Fix below.
>
> Thanks,
>
> 	tglx
>
> 8<--------------------
>
> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> index c5bb63be4ba1..40d5a8a75212 100644
> --- a/arch/x86/kernel/cpu/mtrr/main.c
> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> @@ -237,6 +237,18 @@ set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type typ
>   	stop_machine(mtrr_rendezvous_handler, &data, cpu_online_mask);
>   }
>   
> +static void set_mtrr_cpuslocked(unsigned int reg, unsigned long base,
> +				unsigned long size, mtrr_type type)
> +{
> +	struct set_mtrr_data data = { .smp_reg = reg,
> +				      .smp_base = base,
> +				      .smp_size = size,
> +				      .smp_type = type
> +				    };
> +
> +	stop_machine_cpuslocked(mtrr_rendezvous_handler, &data, cpu_online_mask);
> +}
> +
>   static void set_mtrr_from_inactive_cpu(unsigned int reg, unsigned long base,
>   				      unsigned long size, mtrr_type type)
>   {
> @@ -370,7 +382,7 @@ int mtrr_add_page(unsigned long base, unsigned long size,
>   	/* Search for an empty MTRR */
>   	i = mtrr_if->get_free_region(base, size, replace);
>   	if (i >= 0) {
> -		set_mtrr(i, base, size, type);
> +		set_mtrr_cpuslocked(i, base, size, type);
>   		if (likely(replace < 0)) {
>   			mtrr_usage_table[i] = 1;
>   		} else {
> @@ -378,7 +390,7 @@ int mtrr_add_page(unsigned long base, unsigned long size,
>   			if (increment)
>   				mtrr_usage_table[i]++;
>   			if (unlikely(replace != i)) {
> -				set_mtrr(replace, 0, 0, 0);
> +				set_mtrr_cpuslocked(replace, 0, 0, 0);
>   				mtrr_usage_table[replace] = 0;
>   			}
>   		}
> @@ -506,7 +518,7 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size)
>   		goto out;
>   	}
>   	if (--mtrr_usage_table[reg] < 1)
> -		set_mtrr(reg, 0, 0, 0);
> +		set_mtrr_cpuslocked(reg, 0, 0, 0);
>   	error = reg;
>    out:
>   	mutex_unlock(&mtrr_mutex);

That fix works for me.

Thanks,

Larry