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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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