Re: percpu data for non-existant cpus

Takayoshi Kochi
2003-11-04T01:43:49Z

[-- Attachment #1: Type: Text/Plain, Size: 859 bytes --]

Hi,

From: Jack Steiner <steiner@sgi.com>
Subject: percpu data for non-existant cpus
Date: Mon, 3 Nov 2003 18:55:24 -0600

> It was neccessary in 2.4 to allocate cpu_data areas for
> non-existent cpus. I forget where, but some generic
> initialization code expected to be able to reference cpu_data
> for all cpus up to NR_CPUS.
>
> Does 2.6 have the same requirement or can I allocate cpu_data
> areas only for cpus that exist or might exist (cpu_possible()).

The current discontig (for both 2.4 & 2.6) only allocate
cpu_data on existing nodes (which means existing cpus
eventually), doesn't it?

We've found wrap_mmu_context() refers to all percpu data
and if the any of the cpu_data is not valid,
it may cause panic.

Attached patches are for 2.4 & 2.6, which are harmless
even when percpu data are allocated for non-existing
cpus.

---
Takayoshi Kochi

[-- Attachment #2: wrap_mmu_context-2.4.patch --]
[-- Type: Text/Plain, Size: 395 bytes --]

--- linux-2.4.22/arch/ia64/mm/tlb.c.orig Fri Sep 12 09:45:18 2003
+++ linux-2.4.22/arch/ia64/mm/tlb.c Wed Oct 8 17:56:03 2003
@@ -75,7 +75,7 @@
* and because interrupts are disabled during context switch.
*/
for (i = 0; i < NR_CPUS; ++i)
- if (i != smp_processor_id())
+ if (cpu_online(i) && (i != smp_processor_id()))
cpu_data(i)->need_tlb_flush = 1;
local_flush_tlb_all();
}

[-- Attachment #3: wrap_mmu_context-2.6.patch --]
[-- Type: Text/Plain, Size: 366 bytes --]

--- linux-2.6.0-test6.orig/arch/ia64/mm/tlb.c Sun Sep 28 09:50:38 2003
+++ linux-2.6.0-test6/arch/ia64/mm/tlb.c Wed Oct 8 17:58:42 2003
@@ -77,7 +77,7 @@
{
int cpu = get_cpu(); /* prevent preemption/migration */
for (i = 0; i < NR_CPUS; ++i)
- if (i != cpu)
+ if (cpu_online(i) && (i != cpu))
per_cpu(ia64_need_tlb_flush, i) = 1;
put_cpu();
}