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

[Andrew Morton]

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?


 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();
 }
 
_

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