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SubjectRe: [PATCH v7 1/4] spinlock: A new lockref structure for lockless update of refcount
On Sun, Sep 01, 2013 at 01:13:06AM +0100, Al Viro wrote:

> +static noinline_for_stack
> +char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_spec spec,
> + int depth)
> +{
> + int i, n = 0;
> + const char *s;
> + char *p = buf;
> + const struct dentry *array[4];
> + char c;
> +
> + if (depth < 0) {
> + depth = 1;
> + WARN_ON(1);
> + }
> + if (depth > 4) {
> + depth = 4;
> + WARN_ON(1);
> + }
> +
> + rcu_read_lock();
> + for (i = 0; i < depth; i++) {
> + struct dentry *p = ACCESS_ONCE(d->d_parent);
> + array[i] = d;
> + if (d == p)
> + break;
> + d = p;
> + }
> + if (!i) { /* root dentry has a bloody inconvenient name */
> + i++;
> + goto do_name;
> + }
> + if (i == depth)
> + goto do_name;
> + while (i && n != spec.precision) {
> + if (buf < end)
> + *buf = '/';
> + buf++;
> + n++;
> +do_name:
> + s = ACCESS_ONCE(array[--i]->d_name.name);
> + while (n != spec.precision && (c = *s++) != '\0') {
> + if (buf < end)
> + *buf = c;
> + buf++;
> + n++;
> + }
> + }
> + rcu_read_unlock();

Should one or both of those ACCESS_ONCE()s be an rcu_dereference()?


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