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

On So 29-04-06 23:57:21, 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?

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".

Pavel
--
Thanks for all the (sleeping) penguins.
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