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    SubjectRe: [PATCH 6/11] ksm: remove old stable nodes more thoroughly
    On Mon, 28 Jan 2013, Andrew Morton wrote:
    > On Fri, 25 Jan 2013 18:01:59 -0800 (PST)
    > Hugh Dickins <hughd@google.com> wrote:
    >
    > > +static int remove_all_stable_nodes(void)
    > > +{
    > > + struct stable_node *stable_node;
    > > + int nid;
    > > + int err = 0;
    > > +
    > > + for (nid = 0; nid < nr_node_ids; nid++) {
    > > + while (root_stable_tree[nid].rb_node) {
    > > + stable_node = rb_entry(root_stable_tree[nid].rb_node,
    > > + struct stable_node, node);
    > > + if (remove_stable_node(stable_node)) {
    > > + err = -EBUSY;
    >
    > It's a bit rude to overwrite remove_stable_node()'s return value.

    Well.... yes, but only the tiniest bit rude :)

    >
    > > + break; /* proceed to next nid */
    > > + }
    > > + cond_resched();
    >
    > Why is this here?

    Because we don't have a limit on the length of this loop, and if
    every node which remove_stable_node() finds is already stale, and
    has no rmap_item still attached, then there would be no rescheduling
    point in the unbounded loop without this one. I was taught to worry
    about bad latencies even in unpreemptible kernels.

    Hugh


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