Date: Tue, 9 Feb 2016 13:00:28 +0900
From: Ryota Ozaki <[email protected]>
One fix: psref_class_create needs to return class before fail1.
Oops!
One question: can we destroy objects like this?:
LIST_FOREACH_SAFE(frotz, &frobbotzim.head, frotz_entry, tmp) {
frotz_destroy(frotz);
}
If impossible, please teach me how to destroy all objects in a list
safely with psref.
If you can guarantee that nobody else will try to insert or destroy
new frobbotzim, then that is safe.
Otherwise, hmm... Maybe something like this -- like the way
bridge_clone_destroy/bridge_delete_member already work:
struct frotz {
struct psref_target f_psref;
struct frotz *f_next;
struct frotz **f_prevp;
...
};
static struct {
kmutex_t lock;
pserialize_t psz;
struct psref_class *class;
struct frotz *first;
bool no_more_please;
} frobbotzim __cacheline_aligned;
static void
frobbotzim_destroy(void)
{
struct frotz *frotz;
mutex_enter(&frobbotzim.lock);
/* Prevent creation of new frobbotzim. */
frobbotzim.no_more_please = true;
/* Destroy all existing frobbotzim. */
while ((frotz = frobbotzim.first) != NULL)
frotz_destroy(frotz);
mutex_exit(&frobbotzim.lock);
}
static void
frotz_destroy(struct frotz *frotz)
{
KASSERT(mutex_owned(&frobbotzim.lock));
/* Prevent new references. */
if (frotz->f_next != NULL)
frotz->f_next->f_prevp = frotz->f_prevp;
*frotz->f_prevp = frotz->f_next;
pserialize_perform(frobbotzim.psz);
/* Release lock while we wait for references to drain. */
mutex_exit(&frobbotzim.lock)
/* Wait for existing references to drain. */
psref_target_drain(&frotz->f_psref, frobbotzim.class);
/* Destroy the frotz for real. */
...destroy fields...
kmem_free(frotz, sizeof(*frotz));
/* Reacquire lock for caller. */
mutex_enter(&frobbotzim.lock);
}
(In the example sketch I wrote for frotz_destroy before, I did things
out of order: drained references with psref_target_drain before
preventing new references by removing it from the list. I also forgot
that queue(3) is not pserialize-safe.)
