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Date:      Tue, 13 Dec 2022 16:39:26 -0800
From:      Gleb Smirnoff <glebius@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:  <Y5kbPtkhRGe0ocnl@FreeBSD.org>
In-Reply-To: <202212132047.2BDKl92M065327@gitrepo.freebsd.org>
References:  <202212132047.2BDKl92M065327@gitrepo.freebsd.org>
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  One u_int32_t sneaked in between multiple uint32_t in this change.

On Tue, Dec 13, 2022 at 08:47:09PM +0000, Mateusz Guzik wrote:
M> The branch main has been updated by mjg:
M> 
M> URL: https://cgit.FreeBSD.org/src/commit/?id=e6bc24b0385a166526d20b2eb0cbb6a116350075
M> 
M> commit e6bc24b0385a166526d20b2eb0cbb6a116350075
M> Author:     Mateusz Guzik <mjg@FreeBSD.org>
M> AuthorDate: 2022-12-13 20:42:32 +0000
M> Commit:     Mateusz Guzik <mjg@FreeBSD.org>
M> CommitDate: 2022-12-13 20:46:58 +0000
M> 
M>     kref: switch internal type to atomic_t and bring back const to kref_read
M>     
M>     This unbreak drm-kmod build.
M>     
M>     the const is part of Linux API
M>     
M>     Unfortunately drm-kmod uses hand-rolled refcount* calls on a kref
M>     object. For now go the easy route of keeping it operational by casting
M>     stuff internally.
M>     
M>     The general goal here is to make FreeBSD refcount API use an opaque
M>     type, hence the ongoing removal of hand-rolled accesses.
M>     
M>     Reported by:    emaste
M> ---
M>  sys/compat/linuxkpi/common/include/linux/kref.h | 22 +++++++++++-----------
M>  1 file changed, 11 insertions(+), 11 deletions(-)
M> 
M> diff --git a/sys/compat/linuxkpi/common/include/linux/kref.h b/sys/compat/linuxkpi/common/include/linux/kref.h
M> index 9a6814175223..5a1fd834a58d 100644
M> --- a/sys/compat/linuxkpi/common/include/linux/kref.h
M> +++ b/sys/compat/linuxkpi/common/include/linux/kref.h
M> @@ -44,35 +44,35 @@
M>  
M>  struct kref {
M>  	/* XXX In Linux this is a refcount_t */
M> -	volatile u_int32_t refcount;
M> +	atomic_t refcount;
M>  };
M>  
M>  static inline void
M>  kref_init(struct kref *kref)
M>  {
M>  
M> -	refcount_init(&kref->refcount, 1);
M> +	refcount_init((uint32_t *)&kref->refcount, 1);
M>  }
M>  
M>  static inline unsigned int
M> -kref_read(struct kref *kref)
M> +kref_read(const struct kref *kref)
M>  {
M>  
M> -	return (refcount_load(&kref->refcount));
M> +	return (refcount_load(__DECONST(u_int32_t *, &kref->refcount)));
M>  }
M>  
M>  static inline void
M>  kref_get(struct kref *kref)
M>  {
M>  
M> -	refcount_acquire(&kref->refcount);
M> +	refcount_acquire((uint32_t *)&kref->refcount);
M>  }
M>  
M>  static inline int
M>  kref_put(struct kref *kref, void (*rel)(struct kref *kref))
M>  {
M>  
M> -	if (refcount_release(&kref->refcount)) {
M> +	if (refcount_release((uint32_t *)&kref->refcount)) {
M>  		rel(kref);
M>  		return 1;
M>  	}
M> @@ -84,7 +84,7 @@ kref_put_lock(struct kref *kref, void (*rel)(struct kref *kref),
M>      spinlock_t *lock)
M>  {
M>  
M> -	if (refcount_release(&kref->refcount)) {
M> +	if (refcount_release((uint32_t *)&kref->refcount)) {
M>  		spin_lock(lock);
M>  		rel(kref);
M>  		return (1);
M> @@ -98,7 +98,7 @@ kref_sub(struct kref *kref, unsigned int count,
M>  {
M>  
M>  	while (count--) {
M> -		if (refcount_release(&kref->refcount)) {
M> +		if (refcount_release((uint32_t *)&kref->refcount)) {
M>  			rel(kref);
M>  			return 1;
M>  		}
M> @@ -110,16 +110,16 @@ static inline int __must_check
M>  kref_get_unless_zero(struct kref *kref)
M>  {
M>  
M> -	return refcount_acquire_if_not_zero(&kref->refcount);
M> +	return refcount_acquire_if_not_zero((uint32_t *)&kref->refcount);
M>  }
M>  
M>  static inline int kref_put_mutex(struct kref *kref,
M>      void (*release)(struct kref *kref), struct mutex *lock)
M>  {
M>  	WARN_ON(release == NULL);
M> -	if (unlikely(!refcount_release_if_not_last(&kref->refcount))) {
M> +	if (unlikely(!refcount_release_if_not_last((uint32_t *)&kref->refcount))) {
M>  		mutex_lock(lock);
M> -		if (unlikely(!refcount_release(&kref->refcount))) {
M> +		if (unlikely(!refcount_release((uint32_t *)&kref->refcount))) {
M>  			mutex_unlock(lock);
M>  			return 0;
M>  		}

-- 
Gleb Smirnoff

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