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

[Shaohua Li <shaohua.li@intel.com>]

On Sun, 2006-04-30 at 14:04 +0200, Pavel Machek wrote:
> On So 29-04-06 23:57:21, Andrew Morton wrote:
> > Shaohua Li <shaohua.li@intel.com> 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?
> 
> Certainly better, I'd say.
> 
> > @@ -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();
> 
> But this still scares. It means calling convention is "may enable
> interrupts with >1 cpu, may not with == 1 cpu". 
Below patch should make things clean. How do you think?

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
---

 linux-2.6.17-rc4-mm1-root/arch/i386/kernel/acpi/sleep.c  |   10 +++-------
 linux-2.6.17-rc4-mm1-root/arch/i386/kernel/acpi/wakeup.S |    2 +-
 linux-2.6.17-rc4-mm1-root/arch/i386/mm/init.c            |   13 +------------
 3 files changed, 5 insertions(+), 20 deletions(-)

diff -puN arch/i386/kernel/acpi/wakeup.S~i386_direct_mapping arch/i386/kernel/acpi/wakeup.S
--- linux-2.6.17-rc4-mm1/arch/i386/kernel/acpi/wakeup.S~i386_direct_mapping	2006-05-16 14:52:37.000000000 +0800
+++ linux-2.6.17-rc4-mm1-root/arch/i386/kernel/acpi/wakeup.S	2006-05-16 15:10:57.000000000 +0800
@@ -56,7 +56,7 @@ wakeup_code:
 1:
 
 	# set up page table
-	movl	$swapper_pg_dir-__PAGE_OFFSET, %eax
+	movl	$sleep_pg_dir-__PAGE_OFFSET, %eax
 	movl	%eax, %cr3
 
 	testl	$1, real_efer_save_restore - wakeup_code
diff -puN arch/i386/kernel/acpi/sleep.c~i386_direct_mapping arch/i386/kernel/acpi/sleep.c
--- linux-2.6.17-rc4-mm1/arch/i386/kernel/acpi/sleep.c~i386_direct_mapping	2006-05-16 14:52:51.000000000 +0800
+++ linux-2.6.17-rc4-mm1-root/arch/i386/kernel/acpi/sleep.c	2006-05-17 09:30:26.000000000 +0800
@@ -11,16 +11,14 @@
 #include <linux/cpumask.h>
 
 #include <asm/smp.h>
-#include <asm/tlbflush.h>
 
 /* address in low memory of the wakeup routine. */
 unsigned long acpi_wakeup_address = 0;
 unsigned long acpi_video_flags;
 extern char wakeup_start, wakeup_end;
 
-extern void zap_low_mappings(void);
-
 extern unsigned long FASTCALL(acpi_copy_wakeup_routine(unsigned long));
+char sleep_pg_dir[PAGE_SIZE];
 
 static void init_low_mapping(pgd_t * pgd, int pgd_limit)
 {
@@ -31,8 +29,6 @@ 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();
 }
 
 /**
@@ -45,7 +41,8 @@ int acpi_save_state_mem(void)
 {
 	if (!acpi_wakeup_address)
 		return 1;
-	init_low_mapping(swapper_pg_dir, USER_PTRS_PER_PGD);
+	memcpy(sleep_pg_dir, swapper_pg_dir, PAGE_SIZE);
+	init_low_mapping((pgd_t *)sleep_pg_dir, USER_PTRS_PER_PGD);
 	memcpy((void *)acpi_wakeup_address, &wakeup_start,
 	       &wakeup_end - &wakeup_start);
 	acpi_copy_wakeup_routine(acpi_wakeup_address);
@@ -58,7 +55,6 @@ int acpi_save_state_mem(void)
  */
 void acpi_restore_state_mem(void)
 {
-	zap_low_mappings();
 }
 
 /**
diff -puN arch/i386/mm/init.c~i386_direct_mapping arch/i386/mm/init.c
--- linux-2.6.17-rc4-mm1/arch/i386/mm/init.c~i386_direct_mapping	2006-05-17 09:03:39.000000000 +0800
+++ linux-2.6.17-rc4-mm1-root/arch/i386/mm/init.c	2006-05-17 09:03:49.000000000 +0800
@@ -422,18 +422,7 @@ void zap_low_mappings (void)
 #else
 		set_pgd(swapper_pg_dir+i, __pgd(0));
 #endif
-	/*
-	 * 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();
+	flush_tlb_all();
 }
 
 static int disable_nx __initdata = 0;
_