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Date: Tue, 23 Sep 2014 14:10:31 -0700
From: Kent Overstreet <kmo@...erainc.com>
To: Tejun Heo <tj@...nel.org>
Cc: linux-kernel@...r.kernel.org, axboe@...nel.dk, hch@...radead.org,
hannes@...xchg.org
Subject: Re: [PATCH 3/9] percpu_ref: replace pcpu_ prefix with percpu_
On Tue, Sep 23, 2014 at 01:55:12AM -0400, Tejun Heo wrote:
> percpu_ref uses pcpu_ prefix for internal stuff and percpu_ for
> externally visible ones. This is the same convention used in the
> percpu allocator implementation. It works fine there but percpu_ref
> doesn't have too much internal-only stuff and scattered usages of
> pcpu_ prefix are confusing than helpful.
>
> This patch replaces all pcpu_ prefixes with percpu_. This is pure
> rename and there's no functional change. Note that PCPU_REF_DEAD is
> renamed to __PERCPU_REF_DEAD to signify that the flag is internal.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Kent Overstreet <kmo@...erainc.com>
Reviewed-by: Kent Overstreet <kmo@...erainc.com>
> ---
> include/linux/percpu-refcount.h | 46 ++++++++++++++++-----------------
> lib/percpu-refcount.c | 56 +++++++++++++++++++++--------------------
> 2 files changed, 52 insertions(+), 50 deletions(-)
>
> diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
> index d44b027..3d463a3 100644
> --- a/include/linux/percpu-refcount.h
> +++ b/include/linux/percpu-refcount.h
> @@ -13,7 +13,7 @@
> *
> * The refcount will have a range of 0 to ((1U << 31) - 1), i.e. one bit less
> * than an atomic_t - this is because of the way shutdown works, see
> - * percpu_ref_kill()/PCPU_COUNT_BIAS.
> + * percpu_ref_kill()/PERCPU_COUNT_BIAS.
> *
> * Before you call percpu_ref_kill(), percpu_ref_put() does not check for the
> * refcount hitting 0 - it can't, if it was in percpu mode. percpu_ref_kill()
> @@ -60,7 +60,7 @@ struct percpu_ref {
> * The low bit of the pointer indicates whether the ref is in percpu
> * mode; if set, then get/put will manipulate the atomic_t.
> */
> - unsigned long pcpu_count_ptr;
> + unsigned long percpu_count_ptr;
> percpu_ref_func_t *release;
> percpu_ref_func_t *confirm_kill;
> struct rcu_head rcu;
> @@ -88,26 +88,26 @@ static inline void percpu_ref_kill(struct percpu_ref *ref)
> return percpu_ref_kill_and_confirm(ref, NULL);
> }
>
> -#define PCPU_REF_DEAD 1
> +#define __PERCPU_REF_DEAD 1
>
> /*
> * Internal helper. Don't use outside percpu-refcount proper. The
> * function doesn't return the pointer and let the caller test it for NULL
> * because doing so forces the compiler to generate two conditional
> - * branches as it can't assume that @ref->pcpu_count is not NULL.
> + * branches as it can't assume that @ref->percpu_count is not NULL.
> */
> -static inline bool __pcpu_ref_alive(struct percpu_ref *ref,
> - unsigned long __percpu **pcpu_countp)
> +static inline bool __percpu_ref_alive(struct percpu_ref *ref,
> + unsigned long __percpu **percpu_countp)
> {
> - unsigned long pcpu_ptr = ACCESS_ONCE(ref->pcpu_count_ptr);
> + unsigned long percpu_ptr = ACCESS_ONCE(ref->percpu_count_ptr);
>
> /* paired with smp_store_release() in percpu_ref_reinit() */
> smp_read_barrier_depends();
>
> - if (unlikely(pcpu_ptr & PCPU_REF_DEAD))
> + if (unlikely(percpu_ptr & __PERCPU_REF_DEAD))
> return false;
>
> - *pcpu_countp = (unsigned long __percpu *)pcpu_ptr;
> + *percpu_countp = (unsigned long __percpu *)percpu_ptr;
> return true;
> }
>
> @@ -121,12 +121,12 @@ static inline bool __pcpu_ref_alive(struct percpu_ref *ref,
> */
> static inline void percpu_ref_get(struct percpu_ref *ref)
> {
> - unsigned long __percpu *pcpu_count;
> + unsigned long __percpu *percpu_count;
>
> rcu_read_lock_sched();
>
> - if (__pcpu_ref_alive(ref, &pcpu_count))
> - this_cpu_inc(*pcpu_count);
> + if (__percpu_ref_alive(ref, &percpu_count))
> + this_cpu_inc(*percpu_count);
> else
> atomic_long_inc(&ref->count);
>
> @@ -144,13 +144,13 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
> */
> static inline bool percpu_ref_tryget(struct percpu_ref *ref)
> {
> - unsigned long __percpu *pcpu_count;
> + unsigned long __percpu *percpu_count;
> int ret;
>
> rcu_read_lock_sched();
>
> - if (__pcpu_ref_alive(ref, &pcpu_count)) {
> - this_cpu_inc(*pcpu_count);
> + if (__percpu_ref_alive(ref, &percpu_count)) {
> + this_cpu_inc(*percpu_count);
> ret = true;
> } else {
> ret = atomic_long_inc_not_zero(&ref->count);
> @@ -178,13 +178,13 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
> */
> static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
> {
> - unsigned long __percpu *pcpu_count;
> + unsigned long __percpu *percpu_count;
> int ret = false;
>
> rcu_read_lock_sched();
>
> - if (__pcpu_ref_alive(ref, &pcpu_count)) {
> - this_cpu_inc(*pcpu_count);
> + if (__percpu_ref_alive(ref, &percpu_count)) {
> + this_cpu_inc(*percpu_count);
> ret = true;
> }
>
> @@ -204,12 +204,12 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
> */
> static inline void percpu_ref_put(struct percpu_ref *ref)
> {
> - unsigned long __percpu *pcpu_count;
> + unsigned long __percpu *percpu_count;
>
> rcu_read_lock_sched();
>
> - if (__pcpu_ref_alive(ref, &pcpu_count))
> - this_cpu_dec(*pcpu_count);
> + if (__percpu_ref_alive(ref, &percpu_count))
> + this_cpu_dec(*percpu_count);
> else if (unlikely(atomic_long_dec_and_test(&ref->count)))
> ref->release(ref);
>
> @@ -226,9 +226,9 @@ static inline void percpu_ref_put(struct percpu_ref *ref)
> */
> static inline bool percpu_ref_is_zero(struct percpu_ref *ref)
> {
> - unsigned long __percpu *pcpu_count;
> + unsigned long __percpu *percpu_count;
>
> - if (__pcpu_ref_alive(ref, &pcpu_count))
> + if (__percpu_ref_alive(ref, &percpu_count))
> return false;
> return !atomic_long_read(&ref->count);
> }
> diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
> index 8ef3f5c..5aea6b7 100644
> --- a/lib/percpu-refcount.c
> +++ b/lib/percpu-refcount.c
> @@ -11,8 +11,8 @@
> * percpu counters will all sum to the correct value
> *
> * (More precisely: because moduler arithmatic is commutative the sum of all the
> - * pcpu_count vars will be equal to what it would have been if all the gets and
> - * puts were done to a single integer, even if some of the percpu integers
> + * percpu_count vars will be equal to what it would have been if all the gets
> + * and puts were done to a single integer, even if some of the percpu integers
> * overflow or underflow).
> *
> * The real trick to implementing percpu refcounts is shutdown. We can't detect
> @@ -29,11 +29,12 @@
> * atomic_long_t can't hit 0 before we've added up all the percpu refs.
> */
>
> -#define PCPU_COUNT_BIAS (1LU << (BITS_PER_LONG - 1))
> +#define PERCPU_COUNT_BIAS (1LU << (BITS_PER_LONG - 1))
>
> -static unsigned long __percpu *pcpu_count_ptr(struct percpu_ref *ref)
> +static unsigned long __percpu *percpu_count_ptr(struct percpu_ref *ref)
> {
> - return (unsigned long __percpu *)(ref->pcpu_count_ptr & ~PCPU_REF_DEAD);
> + return (unsigned long __percpu *)
> + (ref->percpu_count_ptr & ~__PERCPU_REF_DEAD);
> }
>
> /**
> @@ -51,10 +52,11 @@ static unsigned long __percpu *pcpu_count_ptr(struct percpu_ref *ref)
> int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release,
> gfp_t gfp)
> {
> - atomic_long_set(&ref->count, 1 + PCPU_COUNT_BIAS);
> + atomic_long_set(&ref->count, 1 + PERCPU_COUNT_BIAS);
>
> - ref->pcpu_count_ptr = (unsigned long)alloc_percpu_gfp(unsigned long, gfp);
> - if (!ref->pcpu_count_ptr)
> + ref->percpu_count_ptr =
> + (unsigned long)alloc_percpu_gfp(unsigned long, gfp);
> + if (!ref->percpu_count_ptr)
> return -ENOMEM;
>
> ref->release = release;
> @@ -74,11 +76,11 @@ EXPORT_SYMBOL_GPL(percpu_ref_init);
> */
> void percpu_ref_exit(struct percpu_ref *ref)
> {
> - unsigned long __percpu *pcpu_count = pcpu_count_ptr(ref);
> + unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
>
> - if (pcpu_count) {
> - free_percpu(pcpu_count);
> - ref->pcpu_count_ptr = PCPU_REF_DEAD;
> + if (percpu_count) {
> + free_percpu(percpu_count);
> + ref->percpu_count_ptr = __PERCPU_REF_DEAD;
> }
> }
> EXPORT_SYMBOL_GPL(percpu_ref_exit);
> @@ -86,14 +88,14 @@ EXPORT_SYMBOL_GPL(percpu_ref_exit);
> static void percpu_ref_kill_rcu(struct rcu_head *rcu)
> {
> struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu);
> - unsigned long __percpu *pcpu_count = pcpu_count_ptr(ref);
> + unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
> unsigned long count = 0;
> int cpu;
>
> for_each_possible_cpu(cpu)
> - count += *per_cpu_ptr(pcpu_count, cpu);
> + count += *per_cpu_ptr(percpu_count, cpu);
>
> - pr_debug("global %ld pcpu %ld",
> + pr_debug("global %ld percpu %ld",
> atomic_long_read(&ref->count), (long)count);
>
> /*
> @@ -108,7 +110,7 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
> * reaching 0 before we add the percpu counts. But doing it at the same
> * time is equivalent and saves us atomic operations:
> */
> - atomic_long_add((long)count - PCPU_COUNT_BIAS, &ref->count);
> + atomic_long_add((long)count - PERCPU_COUNT_BIAS, &ref->count);
>
> WARN_ONCE(atomic_long_read(&ref->count) <= 0,
> "percpu ref (%pf) <= 0 (%ld) after killed",
> @@ -143,10 +145,10 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
> void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
> percpu_ref_func_t *confirm_kill)
> {
> - WARN_ONCE(ref->pcpu_count_ptr & PCPU_REF_DEAD,
> + WARN_ONCE(ref->percpu_count_ptr & __PERCPU_REF_DEAD,
> "%s called more than once on %pf!", __func__, ref->release);
>
> - ref->pcpu_count_ptr |= PCPU_REF_DEAD;
> + ref->percpu_count_ptr |= __PERCPU_REF_DEAD;
> ref->confirm_kill = confirm_kill;
>
> call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu);
> @@ -166,24 +168,24 @@ EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm);
> */
> void percpu_ref_reinit(struct percpu_ref *ref)
> {
> - unsigned long __percpu *pcpu_count = pcpu_count_ptr(ref);
> + unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
> int cpu;
>
> - BUG_ON(!pcpu_count);
> + BUG_ON(!percpu_count);
> WARN_ON_ONCE(!percpu_ref_is_zero(ref));
>
> - atomic_long_set(&ref->count, 1 + PCPU_COUNT_BIAS);
> + atomic_long_set(&ref->count, 1 + PERCPU_COUNT_BIAS);
>
> /*
> * Restore per-cpu operation. smp_store_release() is paired with
> - * smp_read_barrier_depends() in __pcpu_ref_alive() and guarantees
> - * that the zeroing is visible to all percpu accesses which can see
> - * the following PCPU_REF_DEAD clearing.
> + * smp_read_barrier_depends() in __percpu_ref_alive() and
> + * guarantees that the zeroing is visible to all percpu accesses
> + * which can see the following __PERCPU_REF_DEAD clearing.
> */
> for_each_possible_cpu(cpu)
> - *per_cpu_ptr(pcpu_count, cpu) = 0;
> + *per_cpu_ptr(percpu_count, cpu) = 0;
>
> - smp_store_release(&ref->pcpu_count_ptr,
> - ref->pcpu_count_ptr & ~PCPU_REF_DEAD);
> + smp_store_release(&ref->percpu_count_ptr,
> + ref->percpu_count_ptr & ~__PERCPU_REF_DEAD);
> }
> EXPORT_SYMBOL_GPL(percpu_ref_reinit);
> --
> 1.9.3
>
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