On Tue, Sep 17, 2024 at 10:34 PM Boqun Feng <boqun.feng@xxxxxxxxx> wrote:
> +static void hazptr_context_snap_readers_locked(struct hazptr_reader_tree *tree,
> + struct hazptr_context *hzcp)
> +{
> + lockdep_assert_held(hzcp->lock);
> +
> + for (int i = 0; i < HAZPTR_SLOT_PER_CTX; i++) {
> + /*
> + * Pairs with smp_store_release() in hazptr_{clear,free}().
> + *
> + * Ensure
> + *
> + * <reader> <updater>
> + *
> + * [access protected pointers]
> + * hazptr_clear();
> + * smp_store_release()
> + * // in reader scan.
> + * smp_load_acquire(); // is null or unused.
> + * [run callbacks] // all accesses from
> + * // reader must be
> + * // observed.
> + */
> + hazptr_t val = smp_load_acquire(&hzcp->slots[i]);
> +
> + if (!is_null_or_unused(val)) {
> + struct hazptr_slot_snap *snap = &hzcp->snaps[i];
> +
> + // Already in the tree, need to remove first.
> + if (!is_null_or_unused(snap->slot)) {
> + reader_del(tree, snap);
> + }
> + snap->slot = val;
> + reader_add(tree, snap);
> + }
> + }
> +}
Hello
I'm curious about whether there are any possible memory leaks here.
It seems that call_hazptr() never frees the memory until the slot is
set to another valid value.
In the code here, the snap is not deleted when hzcp->snaps[i] is null/unused
and snap->slot is not which I think it should be.
And it can cause unneeded deletion and addition of the snap if the slot
value is unchanged.
I'm not so sure...
Thanks
Lai
