Re: [PATCH 1/2] perf tools: Fix possible compiler warnings in hashmap

[Andrii Nakryiko]

On Fri, Oct 11, 2024 at 9:44 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> On Thu, Oct 10, 2024 at 06:48:26PM -0700, Andrii Nakryiko wrote:
> > On Wed, Oct 9, 2024 at 1:20 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> > >
> > > The hashmap__for_each_entry[_safe] is accessing 'map' as if it's a
> > > pointer.  But it does without parentheses so passing a static hash map
> > > with an ampersand (like &slab_hash below) caused compiler warnings due
> > > to unmatched types.
> > >
> > >   In file included from util/bpf_lock_contention.c:5:
> > >   util/bpf_lock_contention.c: In function ‘exit_slab_cache_iter’:
> > >   linux/tools/perf/util/hashmap.h:169:32: error: invalid type argument of ‘->’ (have ‘struct hashmap’)
> > >     169 |         for (bkt = 0; bkt < map->cap; bkt++)                                \
> > >         |                                ^~
> > >   util/bpf_lock_contention.c:105:9: note: in expansion of macro ‘hashmap__for_each_entry’
> > >     105 |         hashmap__for_each_entry(&slab_hash, cur, bkt)
> > >         |         ^~~~~~~~~~~~~~~~~~~~~~~
> > >   /home/namhyung/project/linux/tools/perf/util/hashmap.h:170:31: error: invalid type argument of ‘->’ (have ‘struct hashmap’)
> > >     170 |                 for (cur = map->buckets[bkt]; cur; cur = cur->next)
> > >         |                               ^~
> > >   util/bpf_lock_contention.c:105:9: note: in expansion of macro ‘hashmap__for_each_entry’
> > >     105 |         hashmap__for_each_entry(&slab_hash, cur, bkt)
> > >         |         ^~~~~~~~~~~~~~~~~~~~~~~
> > >
> > > Cc: bpf@xxxxxxxxxxxxxxx
> > > Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> > > ---
> > > I've discovered this while prototyping the slab symbolization for perf
> > > lock contention.  So this code is not available yet but I'd like to fix
> > > the problem first.
> > >
> > > Also noticed bpf has the same code and the same problem.  I'll send a
> > > separate patch for them.
> > >
> >
> > Yep, please do. Fixes look good, thanks.
>
> Sure will do, can I get your Acked-by for this patch?
>

Sure:

Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>

> Thanks,
> Namhyung
>
> >
> > >  tools/perf/util/hashmap.h | 20 ++++++++++----------
> > >  1 file changed, 10 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/tools/perf/util/hashmap.h b/tools/perf/util/hashmap.h
> > > index c12f8320e6682d50..0c4f155e8eb745d9 100644
> > > --- a/tools/perf/util/hashmap.h
> > > +++ b/tools/perf/util/hashmap.h
> > > @@ -166,8 +166,8 @@ bool hashmap_find(const struct hashmap *map, long key, long *value);
> > >   * @bkt: integer used as a bucket loop cursor
> > >   */
> > >  #define hashmap__for_each_entry(map, cur, bkt)                             \
> > > -       for (bkt = 0; bkt < map->cap; bkt++)                                \
> > > -               for (cur = map->buckets[bkt]; cur; cur = cur->next)
> > > +       for (bkt = 0; bkt < (map)->cap; bkt++)                              \
> > > +               for (cur = (map)->buckets[bkt]; cur; cur = cur->next)
> > >
> > >  /*
> > >   * hashmap__for_each_entry_safe - iterate over all entries in hashmap, safe
> > > @@ -178,8 +178,8 @@ bool hashmap_find(const struct hashmap *map, long key, long *value);
> > >   * @bkt: integer used as a bucket loop cursor
> > >   */
> > >  #define hashmap__for_each_entry_safe(map, cur, tmp, bkt)                   \
> > > -       for (bkt = 0; bkt < map->cap; bkt++)                                \
> > > -               for (cur = map->buckets[bkt];                               \
> > > +       for (bkt = 0; bkt < (map)->cap; bkt++)                              \
> > > +               for (cur = (map)->buckets[bkt];                             \
> > >                      cur && ({tmp = cur->next; true; });                    \
> > >                      cur = tmp)
> > >
> > > @@ -190,19 +190,19 @@ bool hashmap_find(const struct hashmap *map, long key, long *value);
> > >   * @key: key to iterate entries for
> > >   */
> > >  #define hashmap__for_each_key_entry(map, cur, _key)                        \
> > > -       for (cur = map->buckets                                             \
> > > -                    ? map->buckets[hash_bits(map->hash_fn((_key), map->ctx), map->cap_bits)] \
> > > +       for (cur = (map)->buckets                                           \
> > > +                    ? (map)->buckets[hash_bits((map)->hash_fn((_key), (map)->ctx), (map)->cap_bits)] \
> > >                      : NULL;                                                \
> > >              cur;                                                           \
> > >              cur = cur->next)                                               \
> > > -               if (map->equal_fn(cur->key, (_key), map->ctx))
> > > +               if ((map)->equal_fn(cur->key, (_key), (map)->ctx))
> > >
> > >  #define hashmap__for_each_key_entry_safe(map, cur, tmp, _key)              \
> > > -       for (cur = map->buckets                                             \
> > > -                    ? map->buckets[hash_bits(map->hash_fn((_key), map->ctx), map->cap_bits)] \
> > > +       for (cur = (map)->buckets                                           \
> > > +                    ? (map)->buckets[hash_bits((map)->hash_fn((_key), (map)->ctx), (map)->cap_bits)] \
> > >                      : NULL;                                                \
> > >              cur && ({ tmp = cur->next; true; });                           \
> > >              cur = tmp)                                                     \
> > > -               if (map->equal_fn(cur->key, (_key), map->ctx))
> > > +               if ((map)->equal_fn(cur->key, (_key), (map)->ctx))
> > >
> > >  #endif /* __LIBBPF_HASHMAP_H */
> > > --
> > > 2.47.0.rc0.187.ge670bccf7e-goog
> > >
> > >