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oom: fix possible oom_dump_tasks NULL pointer

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When /proc/sys/vm/oom_dump_tasks is enabled, it is possible to get a NULL
pointer for tasks that have detached mm's since task_lock() is not held
during the tasklist scan.  Add the task_lock().

Acked-by: Nick Piggin <npiggin@suse.de>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2009-05-28 14:34:19 -07:00 committed by Linus Torvalds
parent 681a1b4032
commit 6d2661ede5
1 changed files with 15 additions and 9 deletions
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24
mm/oom_kill.c
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@ -284,22 +284,28 @@ static void dump_tasks(const struct mem_cgroup *mem)
printk(KERN_INFO "[ pid ] uid tgid total_vm rss cpu oom_adj "
"name\n");
do_each_thread(g, p) {
/*
* total_vm and rss sizes do not exist for tasks with a
* detached mm so there's no need to report them.
*/
if (!p->mm)
continue;
struct mm_struct *mm;
if (mem && !task_in_mem_cgroup(p, mem))
continue;
if (!thread_group_leader(p))
continue;
task_lock(p);
mm = p->mm;
if (!mm) {
/*
* total_vm and rss sizes do not exist for tasks with no
* mm so there's no need to report them; they can't be
* oom killed anyway.
*/
task_unlock(p);
continue;
}
printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n",
p->pid, __task_cred(p)->uid, p->tgid,
p->mm->total_vm, get_mm_rss(p->mm), (int)task_cpu(p),
p->oomkilladj, p->comm);
p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm,
get_mm_rss(mm), (int)task_cpu(p), p->oomkilladj,
p->comm);
task_unlock(p);
} while_each_thread(g, p);
}