[patch 007/104] cpuset: fix regression when failed to generate sched domains

Greg KH
2008-12-03T19:52:41Z

[-- Attachment #1: cpuset-fix-regression-when-failed-to-generate-sched-domains.patch --]
[-- Type: text/plain, Size: 3134 bytes --]

2.6.27-stable review patch. If anyone has any objections, please let us know.

------------------
From: Li Zefan <lizf@cn.fujitsu.com>

commit 700018e0a77b4113172257fcdaa1c58e27a5074f upstream.

Impact: properly rebuild sched-domains on kmalloc() failure

When cpuset failed to generate sched domains due to kmalloc()
failure, the scheduler should fallback to the single partition
'fallback_doms' and rebuild sched domains, but now it only
destroys but not rebuilds sched domains.

The regression was introduced by:

| commit dfb512ec4834116124da61d6c1ee10fd0aa32bd6
| Author: Max Krasnyansky <maxk@qualcomm.com>
| Date: Fri Aug 29 13:11:41 2008 -0700
|
| sched: arch_reinit_sched_domains() must destroy domains to force rebuild

After the above commit, partition_sched_domains(0, NULL, NULL) will
only destroy sched domains and partition_sched_domains(1, NULL, NULL)
will create the default sched domain.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
kernel/cpuset.c | 12 ++++++++----
kernel/sched.c | 13 +++++++------
2 files changed, 15 insertions(+), 10 deletions(-)

--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -587,7 +587,6 @@ static int generate_sched_domains(cpumas
int ndoms; /* number of sched domains in result */
int nslot; /* next empty doms[] cpumask_t slot */

- ndoms = 0;
doms = NULL;
dattr = NULL;
csa = NULL;
@@ -674,10 +673,8 @@ restart:
* Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
*/
doms = kmalloc(ndoms * sizeof(cpumask_t), GFP_KERNEL);
- if (!doms) {
- ndoms = 0;
+ if (!doms)
goto done;
- }

/*
* The rest of the code, including the scheduler, can deal with
@@ -732,6 +729,13 @@ restart:
done:
kfree(csa);

+ /*
+ * Fallback to the default domain if kmalloc() failed.
+ * See comments in partition_sched_domains().
+ */
+ if (doms == NULL)
+ ndoms = 1;
+
*domains = doms;
*attributes = dattr;
return ndoms;
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7692,13 +7692,14 @@ static int dattrs_equal(struct sched_dom
*
* The passed in 'doms_new' should be kmalloc'd. This routine takes
* ownership of it and will kfree it when done with it. If the caller
- * failed the kmalloc call, then it can pass in doms_new == NULL,
- * and partition_sched_domains() will fallback to the single partition
- * 'fallback_doms', it also forces the domains to be rebuilt.
+ * failed the kmalloc call, then it can pass in doms_new == NULL &&
+ * ndoms_new == 1, and partition_sched_domains() will fallback to
+ * the single partition 'fallback_doms', it also forces the domains
+ * to be rebuilt.
*
- * If doms_new==NULL it will be replaced with cpu_online_map.
- * ndoms_new==0 is a special case for destroying existing domains.
- * It will not create the default domain.
+ * If doms_new == NULL it will be replaced with cpu_online_map.
+ * ndoms_new == 0 is a special case for destroying existing domains,
+ * and it will not create the default domain.
*
* Call with hotplug lock held
*/