Date: Wed, 14 Dec 2022 22:25:23 +0000 From: Alexander Richardson <arichardson@freebsd.org> To: Mateusz Guzik <mjg@freebsd.org> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: e6bc24b0385a - main - kref: switch internal type to atomic_t and bring back const to kref_read Message-ID: <CA%2BZ_v8rw7-UH%2B2n4=Go3JDOwwNvYJC-W666wEAOjCdP%2BnYiJaQ@mail.gmail.com> In-Reply-To: <202212132047.2BDKl92M065327@gitrepo.freebsd.org> References: <202212132047.2BDKl92M065327@gitrepo.freebsd.org>
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On Tue, 13 Dec 2022 at 20:47, Mateusz Guzik <mjg@freebsd.org> wrote: > > The branch main has been updated by mjg: > > URL: https://cgit.FreeBSD.org/src/commit/?id=e6bc24b0385a166526d20b2eb0cbb6a116350075 > > commit e6bc24b0385a166526d20b2eb0cbb6a116350075 > Author: Mateusz Guzik <mjg@FreeBSD.org> > AuthorDate: 2022-12-13 20:42:32 +0000 > Commit: Mateusz Guzik <mjg@FreeBSD.org> > CommitDate: 2022-12-13 20:46:58 +0000 > > kref: switch internal type to atomic_t and bring back const to kref_read > > This unbreak drm-kmod build. > > the const is part of Linux API > > Unfortunately drm-kmod uses hand-rolled refcount* calls on a kref > object. For now go the easy route of keeping it operational by casting > stuff internally. > > The general goal here is to make FreeBSD refcount API use an opaque > type, hence the ongoing removal of hand-rolled accesses. > > Reported by: emaste > --- > sys/compat/linuxkpi/common/include/linux/kref.h | 22 +++++++++++----------- > 1 file changed, 11 insertions(+), 11 deletions(-) > > diff --git a/sys/compat/linuxkpi/common/include/linux/kref.h b/sys/compat/linuxkpi/common/include/linux/kref.h > index 9a6814175223..5a1fd834a58d 100644 > --- a/sys/compat/linuxkpi/common/include/linux/kref.h > +++ b/sys/compat/linuxkpi/common/include/linux/kref.h > @@ -44,35 +44,35 @@ > > struct kref { > /* XXX In Linux this is a refcount_t */ > - volatile u_int32_t refcount; > + atomic_t refcount; > }; > > static inline void > kref_init(struct kref *kref) > { > > - refcount_init(&kref->refcount, 1); > + refcount_init((uint32_t *)&kref->refcount, 1); > } > > static inline unsigned int > -kref_read(struct kref *kref) > +kref_read(const struct kref *kref) > { > > - return (refcount_load(&kref->refcount)); > + return (refcount_load(__DECONST(u_int32_t *, &kref->refcount))); This is rather ugly IMO, can't we change refcount_load() to take a const pointer? It looks like the problem might be __atomic_load_int_relaxed(), but that could use const as well? > } > > static inline void > kref_get(struct kref *kref) > { > > - refcount_acquire(&kref->refcount); > + refcount_acquire((uint32_t *)&kref->refcount); > } > > static inline int > kref_put(struct kref *kref, void (*rel)(struct kref *kref)) > { > > - if (refcount_release(&kref->refcount)) { > + if (refcount_release((uint32_t *)&kref->refcount)) { > rel(kref); > return 1; > } > @@ -84,7 +84,7 @@ kref_put_lock(struct kref *kref, void (*rel)(struct kref *kref), > spinlock_t *lock) > { > > - if (refcount_release(&kref->refcount)) { > + if (refcount_release((uint32_t *)&kref->refcount)) { > spin_lock(lock); > rel(kref); > return (1); > @@ -98,7 +98,7 @@ kref_sub(struct kref *kref, unsigned int count, > { > > while (count--) { > - if (refcount_release(&kref->refcount)) { > + if (refcount_release((uint32_t *)&kref->refcount)) { > rel(kref); > return 1; > } > @@ -110,16 +110,16 @@ static inline int __must_check > kref_get_unless_zero(struct kref *kref) > { > > - return refcount_acquire_if_not_zero(&kref->refcount); > + return refcount_acquire_if_not_zero((uint32_t *)&kref->refcount); > } > > static inline int kref_put_mutex(struct kref *kref, > void (*release)(struct kref *kref), struct mutex *lock) > { > WARN_ON(release == NULL); > - if (unlikely(!refcount_release_if_not_last(&kref->refcount))) { > + if (unlikely(!refcount_release_if_not_last((uint32_t *)&kref->refcount))) { > mutex_lock(lock); > - if (unlikely(!refcount_release(&kref->refcount))) { > + if (unlikely(!refcount_release((uint32_t *)&kref->refcount))) { > mutex_unlock(lock); > return 0; > }
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