[igt-dev] [PATCH i-g-t v26 02/35] lib/igt_list: igt_hlist implementation.
Jason Ekstrand
jason at jlekstrand.net
Wed Mar 17 18:02:53 UTC 2021
On Wed, Mar 17, 2021 at 12:43 PM Zbigniew Kempczyński
<zbigniew.kempczynski at intel.com> wrote:
>
> On Wed, Mar 17, 2021 at 11:43:38AM -0500, Jason Ekstrand wrote:
> > Would it be better to pull the hash table implementation from Mesa?
> > Or use https://cgit.freedesktop.org/~anholt/hash_table/ which should
> > be identical, though it may be a bit out-of-date. I've poured enough
> > hours of my life into finding and fixing the bugs in the Mesa hash
> > table that IGT rolling its own doesn't really fill me with happy
> > feelings.
> >
> > --Jason
>
> I'm not going to be a devil advocate, I'll just ask Dominik how
> confident is he about that implementation, at least we can provide
> some stress test with multithreading scenarios.
>
> He's ported kernel hashtable so if he didn't introduce a non obvious
> bug it should work.
If this is, indeed, a port of the kernel hash table, then it's
probably ok. Not sure how that works out on licenses, but it should
be correct. If this has been freshly hand-rolled expressly for this
purpose, then it makes me nervous.
> Regarding Eric implementation - we need to adopt that implementation
> to at least rename to igt_* and fix the code which is using.
> Should take few days max.
>
> If you'll take a look to tests api_intel_allocator at two-level-inception
> you'll see we're stress testing that hashtable much from many
> processes / threads and we see no problem with losing data coherency
> in the map.
I'm less worried about threads, so long as it's locked, as I am about
weird insert/remove patterns. Most of the bugs I've had to fix in
mesa were because certain patterns of insert/remove with the right
hashes would cause it to blow up. If most of what you do is just add
a bunch of stuff without a lot of removal, they can be unlikely and
hard to find. That said, given that it's linked list based and not
re-hash based, a lot of those corner cases are less likely than they
were with the Mesa implementation. Again, my primary concern is with
a NEW hash table impl. :-)
--Jason
> --
> Zbigniew
> >
> > On Wed, Mar 17, 2021 at 9:46 AM Zbigniew Kempczyński
> > <zbigniew.kempczynski at intel.com> wrote:
> > >
> > > From: Dominik Grzegorzek <dominik.grzegorzek at intel.com>
> > >
> > > Double linked lists with a single pointer list head implementation,
> > > based on similar in the kernel.
> > >
> > > Signed-off-by: Dominik Grzegorzek <dominik.grzegorzek at intel.com>
> > > Cc: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
> > > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > > Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> > > ---
> > > lib/igt_list.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++
> > > lib/igt_list.h | 50 +++++++++++++++++++++++++++++++++--
> > > 2 files changed, 120 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/lib/igt_list.c b/lib/igt_list.c
> > > index 37ae139c4..43200f9b3 100644
> > > --- a/lib/igt_list.c
> > > +++ b/lib/igt_list.c
> > > @@ -22,6 +22,7 @@
> > > *
> > > */
> > >
> > > +#include "assert.h"
> > > #include "igt_list.h"
> > >
> > > void IGT_INIT_LIST_HEAD(struct igt_list_head *list)
> > > @@ -81,3 +82,74 @@ bool igt_list_empty(const struct igt_list_head *head)
> > > {
> > > return head->next == head;
> > > }
> > > +
> > > +void igt_hlist_init(struct igt_hlist_node *h)
> > > +{
> > > + h->next = NULL;
> > > + h->pprev = NULL;
> > > +}
> > > +
> > > +int igt_hlist_unhashed(const struct igt_hlist_node *h)
> > > +{
> > > + return !h->pprev;
> > > +}
> > > +
> > > +int igt_hlist_empty(const struct igt_hlist_head *h)
> > > +{
> > > + return !h->first;
> > > +}
> > > +
> > > +static void __igt_hlist_del(struct igt_hlist_node *n)
> > > +{
> > > + struct igt_hlist_node *next = n->next;
> > > + struct igt_hlist_node **pprev = n->pprev;
> > > +
> > > + *pprev = next;
> > > + if (next)
> > > + next->pprev = pprev;
> > > +}
> > > +
> > > +void igt_hlist_del(struct igt_hlist_node *n)
> > > +{
> > > + __igt_hlist_del(n);
> > > + n->next = NULL;
> > > + n->pprev = NULL;
> > > +}
> > > +
> > > +void igt_hlist_del_init(struct igt_hlist_node *n)
> > > +{
> > > + if (!igt_hlist_unhashed(n)) {
> > > + __igt_hlist_del(n);
> > > + igt_hlist_init(n);
> > > + }
> > > +}
> > > +
> > > +void igt_hlist_add_head(struct igt_hlist_node *n, struct igt_hlist_head *h)
> > > +{
> > > + struct igt_hlist_node *first = h->first;
> > > +
> > > + n->next = first;
> > > + if (first)
> > > + first->pprev = &n->next;
> > > + h->first = n;
> > > + n->pprev = &h->first;
> > > +}
> > > +
> > > +void igt_hlist_add_before(struct igt_hlist_node *n, struct igt_hlist_node *next)
> > > +{
> > > + assert(next);
> > > + n->pprev = next->pprev;
> > > + n->next = next;
> > > + next->pprev = &n->next;
> > > + *(n->pprev) = n;
> > > +}
> > > +
> > > +void igt_hlist_add_behind(struct igt_hlist_node *n, struct igt_hlist_node *prev)
> > > +{
> > > + n->next = prev->next;
> > > + prev->next = n;
> > > + n->pprev = &prev->next;
> > > +
> > > + if (n->next)
> > > + n->next->pprev = &n->next;
> > > +}
> > > diff --git a/lib/igt_list.h b/lib/igt_list.h
> > > index cc93d7a0d..78e761e05 100644
> > > --- a/lib/igt_list.h
> > > +++ b/lib/igt_list.h
> > > @@ -40,6 +40,10 @@
> > > * igt_list is a doubly-linked list where an instance of igt_list_head is a
> > > * head sentinel and has to be initialized.
> > > *
> > > + * igt_hist is also an double linked lists, but with a single pointer list head.
> > > + * Mostly useful for hash tables where the two pointer list head is
> > > + * too wasteful. You lose the ability to access the tail in O(1).
> > > + *
> > > * Example usage:
> > > *
> > > * |[<!-- language="C" -->
> > > @@ -71,6 +75,13 @@ struct igt_list_head {
> > > struct igt_list_head *next;
> > > };
> > >
> > > +struct igt_hlist_head {
> > > + struct igt_hlist_node *first;
> > > +};
> > > +
> > > +struct igt_hlist_node {
> > > + struct igt_hlist_node *next, **pprev;
> > > +};
> > >
> > > void IGT_INIT_LIST_HEAD(struct igt_list_head *head);
> > > void igt_list_add(struct igt_list_head *elem, struct igt_list_head *head);
> > > @@ -81,6 +92,17 @@ void igt_list_move_tail(struct igt_list_head *elem, struct igt_list_head *list);
> > > int igt_list_length(const struct igt_list_head *head);
> > > bool igt_list_empty(const struct igt_list_head *head);
> > >
> > > +void igt_hlist_init(struct igt_hlist_node *h);
> > > +int igt_hlist_unhashed(const struct igt_hlist_node *h);
> > > +int igt_hlist_empty(const struct igt_hlist_head *h);
> > > +void igt_hlist_del(struct igt_hlist_node *n);
> > > +void igt_hlist_del_init(struct igt_hlist_node *n);
> > > +void igt_hlist_add_head(struct igt_hlist_node *n, struct igt_hlist_head *h);
> > > +void igt_hlist_add_before(struct igt_hlist_node *n,
> > > + struct igt_hlist_node *next);
> > > +void igt_hlist_add_behind(struct igt_hlist_node *n,
> > > + struct igt_hlist_node *prev);
> > > +
> > > #define igt_container_of(ptr, sample, member) \
> > > (__typeof__(sample))((char *)(ptr) - \
> > > offsetof(__typeof__(*sample), member))
> > > @@ -96,9 +118,10 @@ bool igt_list_empty(const struct igt_list_head *head);
> > > * Safe against removel of the *current* list element. To achive this it
> > > * requires an extra helper variable `tmp` with the same type as `pos`.
> > > */
> > > -#define igt_list_for_each_entry_safe(pos, tmp, head, member) \
> > > +
> > > +#define igt_list_for_each_entry_safe(pos, tmp, head, member) \
> > > for (pos = igt_container_of((head)->next, pos, member), \
> > > - tmp = igt_container_of((pos)->member.next, tmp, member); \
> > > + tmp = igt_container_of((pos)->member.next, tmp, member); \
> > > &pos->member != (head); \
> > > pos = tmp, \
> > > tmp = igt_container_of((pos)->member.next, tmp, member))
> > > @@ -108,6 +131,27 @@ bool igt_list_empty(const struct igt_list_head *head);
> > > &pos->member != (head); \
> > > pos = igt_container_of((pos)->member.prev, pos, member))
> > >
> > > +#define igt_list_for_each_entry_safe_reverse(pos, tmp, head, member) \
> > > + for (pos = igt_container_of((head)->prev, pos, member), \
> > > + tmp = igt_container_of((pos)->member.prev, tmp, member); \
> > > + &pos->member != (head); \
> > > + pos = tmp, \
> > > + tmp = igt_container_of((pos)->member.prev, tmp, member))
> > > +
> > > +#define igt_hlist_entry_safe(ptr, sample, member) \
> > > + ({ typeof(ptr) ____ptr = (ptr); \
> > > + ____ptr ? igt_container_of(____ptr, sample, member) : NULL; \
> > > + })
> > > +
> > > +#define igt_hlist_for_each_entry(pos, head, member) \
> > > + for (pos = igt_hlist_entry_safe((head)->first, pos, member); \
> > > + pos; \
> > > + pos = igt_hlist_entry_safe((pos)->member.next, pos, member))
> > > +
> > > +#define igt_hlist_for_each_entry_safe(pos, n, head, member) \
> > > + for (pos = igt_hlist_entry_safe((head)->first, pos, member); \
> > > + pos && ({ n = pos->member.next; 1; }); \
> > > + pos = igt_hlist_entry_safe(n, pos, member))
> > >
> > > /* IGT custom helpers */
> > >
> > > @@ -127,4 +171,6 @@ bool igt_list_empty(const struct igt_list_head *head);
> > > #define igt_list_last_entry(head, type, member) \
> > > igt_container_of((head)->prev, (type), member)
> > >
> > > +#define IGT_INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
> > > +
> > > #endif /* IGT_LIST_H */
> > > --
> > > 2.26.0
> > >
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