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Subject[tip:sched/urgent] sched: Fix OOPS when build_sched_domains() percpu allocation fails
Commit-ID:  fb2cf2c660971bea0ad86a9a5c19ad39eab61344
Gitweb: http://git.kernel.org/tip/fb2cf2c660971bea0ad86a9a5c19ad39eab61344
Author: he, bo <bo.he@intel.com>
AuthorDate: Wed, 25 Apr 2012 19:59:21 +0800
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 26 Apr 2012 12:54:53 +0200

sched: Fix OOPS when build_sched_domains() percpu allocation fails

Under extreme memory used up situations, percpu allocation
might fail. We hit it when system goes to suspend-to-ram,
causing a kworker panic:

EIP: [<c124411a>] build_sched_domains+0x23a/0xad0
Kernel panic - not syncing: Fatal exception
Pid: 3026, comm: kworker/u:3
3.0.8-137473-gf42fbef #1

Call Trace:
[<c18cc4f2>] panic+0x66/0x16c
[...]
[<c1244c37>] partition_sched_domains+0x287/0x4b0
[<c12a77be>] cpuset_update_active_cpus+0x1fe/0x210
[<c123712d>] cpuset_cpu_inactive+0x1d/0x30
[...]

With this fix applied build_sched_domains() will return -ENOMEM and
the suspend attempt fails.

Signed-off-by: he, bo <bo.he@intel.com>
Reviewed-by: Zhang, Yanmin <yanmin.zhang@intel.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/1335355161.5892.17.camel@hebo
[ So, we fail to deallocate a CPU because we cannot allocate RAM :-/
I don't like that kind of sad behavior but nevertheless it should
not crash under high memory load. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/core.c | 22 ++++++++++++++++------
1 files changed, 16 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4603b9d..0533a68 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6405,16 +6405,26 @@ static void __sdt_free(const struct cpumask *cpu_map)
struct sd_data *sdd = &tl->data;

for_each_cpu(j, cpu_map) {
- struct sched_domain *sd = *per_cpu_ptr(sdd->sd, j);
- if (sd && (sd->flags & SD_OVERLAP))
- free_sched_groups(sd->groups, 0);
- kfree(*per_cpu_ptr(sdd->sd, j));
- kfree(*per_cpu_ptr(sdd->sg, j));
- kfree(*per_cpu_ptr(sdd->sgp, j));
+ struct sched_domain *sd;
+
+ if (sdd->sd) {
+ sd = *per_cpu_ptr(sdd->sd, j);
+ if (sd && (sd->flags & SD_OVERLAP))
+ free_sched_groups(sd->groups, 0);
+ kfree(*per_cpu_ptr(sdd->sd, j));
+ }
+
+ if (sdd->sg)
+ kfree(*per_cpu_ptr(sdd->sg, j));
+ if (sdd->sgp)
+ kfree(*per_cpu_ptr(sdd->sgp, j));
}
free_percpu(sdd->sd);
+ sdd->sd = NULL;
free_percpu(sdd->sg);
+ sdd->sg = NULL;
free_percpu(sdd->sgp);
+ sdd->sgp = NULL;
}
}


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