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| author |   Rik van Riel <riel@redhat.com> | 2013-11-11 19:29:25 -0500 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2013-11-13 13:33:51 +0100 |
| commit | 46a73e8a1c1720f7713b5e2df68e9dd272015b5d (patch) | |
| tree | a119f949799e3cd7382548eac2b41fa060c29ac5 /kernel | |
| parent | sched: Fix endless sync_sched/rcu() loop inside _cpu_down() (diff) | |
| download | linux-dev-46a73e8a1c1720f7713b5e2df68e9dd272015b5d.tar.xz linux-dev-46a73e8a1c1720f7713b5e2df68e9dd272015b5d.zip | |
sched/numa: Fix NULL pointer dereference in task_numa_migrate()
The cpusets code can split up the scheduler's domain tree into
smaller domains. Some of those smaller domains may not cross
NUMA nodes at all, leading to a NULL pointer dereference on the
per-cpu sd_numa pointer.
Tasks cannot be migrated out of their domain, so the patch
also sets p->numa_preferred_nid to whereever they are, to
prevent the migration from being retried over and over again.
Reported-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Link: http://lkml.kernel.org/n/tip-oosqomw0Jput0Jkvoowhrqtu@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index df77c605c7a6..c11e36ff5ea0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1201,9 +1201,21 @@ static int task_numa_migrate(struct task_struct *p) */ rcu_read_lock(); sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu)); - env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; + if (sd) + env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; rcu_read_unlock(); + /* + * Cpusets can break the scheduler domain tree into smaller + * balance domains, some of which do not cross NUMA boundaries. + * Tasks that are "trapped" in such domains cannot be migrated + * elsewhere, so there is no point in (re)trying. + */ + if (unlikely(!sd)) { + p->numa_preferred_nid = cpu_to_node(task_cpu(p)); + return -EINVAL; + } + taskweight = task_weight(p, env.src_nid); groupweight = group_weight(p, env.src_nid); update_numa_stats(&env.src_stats, env.src_nid); |