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Message-ID: <49225A5B.6080103@cn.fujitsu.com>
Date: Tue, 18 Nov 2008 14:02:03 +0800
From: Li Zefan <lizf@...fujitsu.com>
To: Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>
CC: Max Krasnyansky <maxk@...lcomm.com>,
Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
Paul Menage <menage@...gle.com>,
LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] cpuset: fix regression when failed to generate sched domains
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 is introduced by:
commit dfb512ec4834116124da61d6c1ee10fd0aa32bd6
Author: Max Krasnyansky <maxk@...lcomm.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@...fujitsu.com>
---
Should I also CC stable for 2.6.27.xx ?
---
kernel/cpuset.c | 12 ++++++++----
kernel/sched.c | 13 +++++++------
2 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 3e00526..81fc679 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -587,7 +587,6 @@ static int generate_sched_domains(cpumask_t **domains,
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;
diff --git a/kernel/sched.c b/kernel/sched.c
index c94baf2..9b1e793 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7789,13 +7789,14 @@ static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
*
* 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
*/
--
1.5.4.rc3
--
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