Re: [PATCH] don't use flush_tlb_all in suspend time

[Shaohua Li]

On Sat, 2006-04-29 at 23:57 -0700, Andrew Morton wrote:
> Shaohua Li <shaohua.li@xxxxxxxxx> wrote:
> >
> > On Sun, 2006-04-30 at 06:45 +0000, Pavel Machek wrote:
> > > Hi!
> > > 
> > > > flush_tlb_all uses on_each_cpu, which will disable/enable interrupt.
> > > > In suspend/resume time, this will make interrupt wrongly enabled.
> > > 
> > > > diff -puN arch/i386/mm/init.c~flush_tlb_all_check arch/i386/mm/init.c
> > > > --- linux-2.6.17-rc3/arch/i386/mm/init.c~flush_tlb_all_check	2006-04-29 08:47:05.000000000 +0800
> > > > +++ linux-2.6.17-rc3-root/arch/i386/mm/init.c	2006-04-29 08:48:15.000000000 +0800
> > > > @@ -420,7 +420,10 @@ void zap_low_mappings (void)
> > > >  #else
> > > >  		set_pgd(swapper_pg_dir+i, __pgd(0));
> > > >  #endif
> > > > -	flush_tlb_all();
> > > > +	if (cpus_weight(cpu_online_map) == 1)
> > > > +		local_flush_tlb();
> > > > +	else
> > > > +		flush_tlb_all();
> > > >  }
> > > >
> > > 
> > > Either it is okay to enable interrupts here -> unneccessary and ugly
> > > test, or it is not, and then we are broken in SMP case.
> > It's not broken in SMP case, APs are offlined here in suspend/resume.
> > 
> 
> In which case, how's about this?
Yes, this is great. Thanks!


>  arch/i386/kernel/acpi/sleep.c   |    3 +++
>  arch/i386/mm/init.c             |   10 +++++++++-
>  arch/x86_64/kernel/acpi/sleep.c |    3 +++
>  3 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff -puN arch/i386/kernel/acpi/sleep.c~dont-use-flush_tlb_all-in-suspend-time-tidy arch/i386/kernel/acpi/sleep.c
> --- devel/arch/i386/kernel/acpi/sleep.c~dont-use-flush_tlb_all-in-suspend-time-tidy	2006-04-29 23:53:33.000000000 -0700
> +++ devel-akpm/arch/i386/kernel/acpi/sleep.c	2006-04-29 23:54:09.000000000 -0700
> @@ -8,6 +8,8 @@
>  #include <linux/acpi.h>
>  #include <linux/bootmem.h>
>  #include <linux/dmi.h>
> +#include <linux/cpumask.h>
> +
>  #include <asm/smp.h>
>  #include <asm/tlbflush.h>
>  
> @@ -29,6 +31,7 @@ static void init_low_mapping(pgd_t * pgd
>  		set_pgd(pgd, *(pgd + USER_PTRS_PER_PGD));
>  		pgd_ofs++, pgd++;
>  	}
> +	WARN_ON(num_online_cpus() != 1);
>  	local_flush_tlb();
>  }
>  
> diff -puN arch/i386/mm/init.c~dont-use-flush_tlb_all-in-suspend-time-tidy arch/i386/mm/init.c
> --- devel/arch/i386/mm/init.c~dont-use-flush_tlb_all-in-suspend-time-tidy	2006-04-29 23:53:33.000000000 -0700
> +++ devel-akpm/arch/i386/mm/init.c	2006-04-29 23:56:00.000000000 -0700
> @@ -29,6 +29,7 @@
>  #include <linux/efi.h>
>  #include <linux/memory_hotplug.h>
>  #include <linux/initrd.h>
> +#include <linux/cpumask.h>
>  
>  #include <asm/processor.h>
>  #include <asm/system.h>
> @@ -420,7 +421,14 @@ void zap_low_mappings (void)
>  #else
>  		set_pgd(swapper_pg_dir+i, __pgd(0));
>  #endif
> -	if (cpus_weight(cpu_online_map) == 1)
> +	/*
> +	 * We can be called at suspend/resume time, with local interrupts
> +	 * disabled.  But flush_tlb_all() requires that local interrupts be
> +	 * enabled.
> +	 *
> +	 * Happily, the APs are not yet started, so we can use local_flush_tlb()	 * in that case
> +	 */
> +	if (num_online_cpus() == 1)
>  		local_flush_tlb();
>  	else
>  		flush_tlb_all();
> diff -puN arch/x86_64/kernel/acpi/sleep.c~dont-use-flush_tlb_all-in-suspend-time-tidy arch/x86_64/kernel/acpi/sleep.c
> --- devel/arch/x86_64/kernel/acpi/sleep.c~dont-use-flush_tlb_all-in-suspend-time-tidy	2006-04-29 23:53:33.000000000 -0700
> +++ devel-akpm/arch/x86_64/kernel/acpi/sleep.c	2006-04-29 23:56:24.000000000 -0700
> @@ -35,6 +35,8 @@
>  #include <linux/pci.h>
>  #include <linux/bootmem.h>
>  #include <linux/acpi.h>
> +#include <linux/cpumask.h>
> +
>  #include <asm/mpspec.h>
>  #include <asm/io.h>
>  #include <asm/apic.h>
> @@ -66,6 +68,7 @@ static void init_low_mapping(void)
>  	pgd_t *slot0 = pgd_offset(current->mm, 0UL);
>  	low_ptr = *slot0;
>  	set_pgd(slot0, *pgd_offset(current->mm, PAGE_OFFSET));
> +	WARN_ON(num_online_cpus() != 1);
>  	local_flush_tlb();
>  }
>  
> _
-- 
Shaohua Li <shaohua.li@xxxxxxxxx>

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