[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))

[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]

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 <acme@redhat.com>
---


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;

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))

[Chris Wright]

* Arnaldo Carvalho de Melo (acme@redhat.com) 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 <acme@redhat.com>

Acked-by: Chris Wright <chrisw@sous-sol.org>

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