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SubjectRe: [patch] mm, hugetlb: add thread name and pid to SHM_HUGETLB mlock rlimit warning
On Tue, 6 Mar 2012 18:26:11 -0800 (PST)
David Rientjes <rientjes@google.com> wrote:

> Add the thread name and pid of the application that is allocating shm
> segments with MAP_HUGETLB without being a part of
> /proc/sys/vm/hugetlb_shm_group or having CAP_IPC_LOCK.
>
> This identifies the application so it may be fixed by avoiding using the
> deprecated exception (see Documentation/feature-removal-schedule.txt).
>
> ...
>
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -946,7 +946,11 @@ struct file *hugetlb_file_setup(const char *name, size_t size,
> if (creat_flags == HUGETLB_SHMFS_INODE && !can_do_hugetlb_shm()) {
> *user = current_user();
> if (user_shm_lock(size, *user)) {
> - printk_once(KERN_WARNING "Using mlock ulimits for SHM_HUGETLB is deprecated\n");
> + task_lock(current);
> + printk_once(KERN_WARNING
> + "%s (%d): Using mlock ulimits for SHM_HUGETLB is deprecated\n",
> + current->comm, current->pid);
> + task_unlock(current);

I assume the task_lock() is there to protect current->comm. If so, it
is unneeded - we're protecting against prctl(PR_SET_NAME), and
PR_SET_NAME only operates on current, and we know this task isn't
currently running PR_SET_NAME.

If there's a way for another task to alter this task's ->comm then we
_do_ need locking. But there isn't a way, I hope.



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