2007-05-31 02:24:45

by Arnaldo Carvalho de Melo

Subject: [PATCH][OPROFILE] x86: Use for_each_possible_cpu to allocate msrs (was [PATCH] x86: fix oprofile double free (was Re: Multiple free during oprofile unload))

The fix for the fix needed a fix: allocate_msrs() was using
for_each_online_cpu(), but nmi_setup uses for_each_possible_cpu(), and
in my test machine, a Dell Poweredge 1950 I have 2 dual core Xeons,
which makes for 4 possible cores, but wait, they are HT capable, so...

[acme@mica linux-2.6.21.3.orig]$ dmesg | grep Allowing
SMP: Allowing 8 CPUs, 4 hotplug CPUs
[acme@mica linux-2.6.21.3.orig]$

We have 8 possible CPUs, but only 4 online, b00m. Fix it by making
allocate_msrs agree with nmi_setup, i.e. make both use
for_each_possible_cpu().

Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---


diff -uNrp linux-2.6.21.3.orig/arch/i386/oprofile/nmi_int.c linux-2.6.21.3.new/arch/i386/oprofile/nmi_int.c
--- linux-2.6.21.3.orig/arch/i386/oprofile/nmi_int.c 2007-05-30 23:08:33.000000000 -0300
+++ linux-2.6.21.3.new/arch/i386/oprofile/nmi_int.c 2007-05-30 23:09:17.000000000 -0300
@@ -154,7 +154,7 @@ static int allocate_msrs(void)
size_t counters_size = sizeof(struct op_msr) * model->num_counters;

int i;
- for_each_online_cpu(i) {
+ for_each_possible_cpu(i) {
cpu_msrs[i].counters = kmalloc(counters_size, GFP_KERNEL);
if (!cpu_msrs[i].counters) {
success = 0;

2007-05-31 06:11:05

by Chris Wright

Subject: Re: [PATCH][OPROFILE] x86: Use for_each_possible_cpu to allocate msrs (was [PATCH] x86: fix oprofile double free (was Re: Multiple free during oprofile unload))

* Arnaldo Carvalho de Melo ([email protected]) wrote:
> The fix for the fix needed a fix: allocate_msrs() was using
> for_each_online_cpu(), but nmi_setup uses for_each_possible_cpu(), and
> in my test machine, a Dell Poweredge 1950 I have 2 dual core Xeons,
> which makes for 4 possible cores, but wait, they are HT capable, so...
>
> [acme@mica linux-2.6.21.3.orig]$ dmesg | grep Allowing
> SMP: Allowing 8 CPUs, 4 hotplug CPUs
> [acme@mica linux-2.6.21.3.orig]$
>
> We have 8 possible CPUs, but only 4 online, b00m. Fix it by making
> allocate_msrs agree with nmi_setup, i.e. make both use
> for_each_possible_cpu().
>
> Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Acked-by: Chris Wright <[email protected]>

Thanks Arnaldo. I noticed this earlier, but mistakenly didn't consider it
an issue aside of code needing to be cleaned up and for hotplug (which I
thought was already broken for other reasons). And the Opteron I tested
on has possible == online. I tested this addition on both the AMD box,
as well as an Intel box with possible > online. All looks good.

thanks,
-chris