Re: [PATCH] isolcpus option broken in 2.6.10-rc2-bk2

[Nick Piggin]

Ingo Molnar wrote:

> * Dimitri Sivanich <sivanich@xxxxxxx> wrote:
>
>
> > The isolcpus option is broken in 2.6.10-rc2-bk2.  The domains are no longer
> > being properly initialized (which results in a panic at bootup).
> >
> > The following patch fixes this.
> >
> > Signed-off-by: Dimitri Sivanich <sivanich@xxxxxxx>
>
> Acked-by: Ingo Molnar <mingo@xxxxxxx>
>
> only a minor nit:
>
>
> > +	/* Initialize isolated CPU (physical) domains and groups */
> > +	for_each_cpu_mask(i, cpu_isolated_map) {
> > +		struct sched_domain *sd = NULL;
>
> there's no need to initialize 'sd' to NULL here.
>
>
> > +		int group;
> > +
> > +		sd = &per_cpu(phys_domains, i);
> > +		group = cpu_to_phys_group(i);
>
> > +	for_each_cpu_mask(i, cpu_isolated_map) {
> > +		struct sched_domain *sd = NULL;
>
> ditto.
>
>
> > +		int group;
> > +
> > +		sd = &per_cpu(phys_domains, i);
> > +		group = cpu_to_phys_group(i);
> > +		*sd = SD_CPU_INIT;
>
> 	Ingo

Actually, this is wrong. And I was wrong to say that the fix was
to initialize the dummy domain (because its ->flags are 0, there
is no need for it to have anything else set up).

The isolated domains don't need to be set up because they correctly
point to the dummy domain, which is already set up properly (zeroed).
The oops is just a problem with sched_domain_debug.

Andrew and/or Linus, please make sure Dimitri's patch gets reverted
and the attached one applied before 2.6.10.



Fix an oops in sched_domain_debug when using the isolcpus= option.

Also move a debug check for validating groups into the "for-each-group"
loop, where it should be.

Signed-off-by: Nick Piggin <nickpiggin@xxxxxxxxxxxx>


---

 linux-2.6-npiggin/kernel/sched.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff -puN kernel/sched.c~sched-debug-oops kernel/sched.c
--- linux-2.6/kernel/sched.c~sched-debug-oops	2004-12-08 19:51:48.000000000 +1100
+++ linux-2.6-npiggin/kernel/sched.c	2004-12-08 19:53:23.000000000 +1100
@@ -4446,6 +4446,7 @@ static void sched_domain_debug(void)
 				if (sd->parent)
 					printk(" ERROR !SD_LOAD_BALANCE domain has parent");
 				printk("\n");
+				break;
 			}
 
 			printk("span %s\n", str);
@@ -4454,8 +4455,6 @@ static void sched_domain_debug(void)
 				printk(KERN_DEBUG "ERROR domain->span does not contain CPU%d\n", i);
 			if (!cpu_isset(i, group->cpumask))
 				printk(KERN_DEBUG "ERROR domain->groups does not contain CPU%d\n", i);
-			if (!group->cpu_power)
-				printk(KERN_DEBUG "ERROR domain->cpu_power not set\n");
 
 			printk(KERN_DEBUG);
 			for (j = 0; j < level + 2; j++)
@@ -4466,6 +4465,9 @@ static void sched_domain_debug(void)
 					printk(" ERROR: NULL");
 					break;
 				}
+				
+				if (!group->cpu_power)
+					printk(KERN_DEBUG "ERROR group->cpu_power not set\n");
 
 				if (!cpus_weight(group->cpumask))
 					printk(" ERROR empty group:");

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