diff options
Diffstat (limited to 'include/linux/percpu-refcount.h')
| -rw-r--r-- | include/linux/percpu-refcount.h | 137 |
1 files changed, 85 insertions, 52 deletions
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index b297cd1cd4f1..d73a1c08c3e3 100644 --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -51,9 +51,9 @@ #define _LINUX_PERCPU_REFCOUNT_H #include <linux/atomic.h> -#include <linux/kernel.h> #include <linux/percpu.h> #include <linux/rcupdate.h> +#include <linux/types.h> #include <linux/gfp.h> struct percpu_ref; @@ -75,27 +75,47 @@ enum { * operation using percpu_ref_switch_to_percpu(). If initialized * with this flag, the ref will stay in atomic mode until * percpu_ref_switch_to_percpu() is invoked on it. + * Implies ALLOW_REINIT. */ PERCPU_REF_INIT_ATOMIC = 1 << 0, /* * Start dead w/ ref == 0 in atomic mode. Must be revived with - * percpu_ref_reinit() before used. Implies INIT_ATOMIC. + * percpu_ref_reinit() before used. Implies INIT_ATOMIC and + * ALLOW_REINIT. */ PERCPU_REF_INIT_DEAD = 1 << 1, + + /* + * Allow switching from atomic mode to percpu mode. + */ + PERCPU_REF_ALLOW_REINIT = 1 << 2, }; -struct percpu_ref { +struct percpu_ref_data { atomic_long_t count; + percpu_ref_func_t *release; + percpu_ref_func_t *confirm_switch; + bool force_atomic:1; + bool allow_reinit:1; + struct rcu_head rcu; + struct percpu_ref *ref; +}; + +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 percpu_count_ptr; - percpu_ref_func_t *release; - percpu_ref_func_t *confirm_switch; - bool force_atomic:1; - struct rcu_head rcu; + + /* + * 'percpu_ref' is often embedded into user structure, and only + * 'percpu_count_ptr' is required in fast path, move other fields + * into 'percpu_ref_data', so we can reduce memory footprint in + * fast path. + */ + struct percpu_ref_data *data; }; int __must_check percpu_ref_init(struct percpu_ref *ref, @@ -110,6 +130,7 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_func_t *confirm_kill); void percpu_ref_resurrect(struct percpu_ref *ref); void percpu_ref_reinit(struct percpu_ref *ref); +bool percpu_ref_is_zero(struct percpu_ref *ref); /** * percpu_ref_kill - drop the initial ref @@ -147,7 +168,7 @@ static inline bool __ref_is_percpu(struct percpu_ref *ref, * between contaminating the pointer value, meaning that * READ_ONCE() is required when fetching it. * - * The smp_read_barrier_depends() implied by READ_ONCE() pairs + * The dependency ordering from the READ_ONCE() pairs * with smp_store_release() in __percpu_ref_switch_to_percpu(). */ percpu_ptr = READ_ONCE(ref->percpu_count_ptr); @@ -178,21 +199,21 @@ static inline void percpu_ref_get_many(struct percpu_ref *ref, unsigned long nr) { unsigned long __percpu *percpu_count; - rcu_read_lock_sched(); + rcu_read_lock(); if (__ref_is_percpu(ref, &percpu_count)) this_cpu_add(*percpu_count, nr); else - atomic_long_add(nr, &ref->count); + atomic_long_add(nr, &ref->data->count); - rcu_read_unlock_sched(); + rcu_read_unlock(); } /** * percpu_ref_get - increment a percpu refcount * @ref: percpu_ref to get * - * Analagous to atomic_long_inc(). + * Analogous to atomic_long_inc(). * * This function is safe to call as long as @ref is between init and exit. */ @@ -202,34 +223,72 @@ static inline void percpu_ref_get(struct percpu_ref *ref) } /** - * percpu_ref_tryget - try to increment a percpu refcount + * percpu_ref_tryget_many - try to increment a percpu refcount * @ref: percpu_ref to try-get + * @nr: number of references to get * - * Increment a percpu refcount unless its count already reached zero. + * Increment a percpu refcount by @nr unless its count already reached zero. * Returns %true on success; %false on failure. * * This function is safe to call as long as @ref is between init and exit. */ -static inline bool percpu_ref_tryget(struct percpu_ref *ref) +static inline bool percpu_ref_tryget_many(struct percpu_ref *ref, + unsigned long nr) { unsigned long __percpu *percpu_count; bool ret; - rcu_read_lock_sched(); + rcu_read_lock(); if (__ref_is_percpu(ref, &percpu_count)) { - this_cpu_inc(*percpu_count); + this_cpu_add(*percpu_count, nr); ret = true; } else { - ret = atomic_long_inc_not_zero(&ref->count); + ret = atomic_long_add_unless(&ref->data->count, nr, 0); } - rcu_read_unlock_sched(); + rcu_read_unlock(); return ret; } /** + * percpu_ref_tryget - try to increment a percpu refcount + * @ref: percpu_ref to try-get + * + * Increment a percpu refcount unless its count already reached zero. + * Returns %true on success; %false on failure. + * + * This function is safe to call as long as @ref is between init and exit. + */ +static inline bool percpu_ref_tryget(struct percpu_ref *ref) +{ + return percpu_ref_tryget_many(ref, 1); +} + +/** + * percpu_ref_tryget_live_rcu - same as percpu_ref_tryget_live() but the + * caller is responsible for taking RCU. + * + * This function is safe to call as long as @ref is between init and exit. + */ +static inline bool percpu_ref_tryget_live_rcu(struct percpu_ref *ref) +{ + unsigned long __percpu *percpu_count; + bool ret = false; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + if (likely(__ref_is_percpu(ref, &percpu_count))) { + this_cpu_inc(*percpu_count); + ret = true; + } else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) { + ret = atomic_long_inc_not_zero(&ref->data->count); + } + return ret; +} + +/** * percpu_ref_tryget_live - try to increment a live percpu refcount * @ref: percpu_ref to try-get * @@ -246,20 +305,11 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref) */ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref) { - unsigned long __percpu *percpu_count; bool ret = false; - rcu_read_lock_sched(); - - if (__ref_is_percpu(ref, &percpu_count)) { - this_cpu_inc(*percpu_count); - ret = true; - } else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) { - ret = atomic_long_inc_not_zero(&ref->count); - } - - rcu_read_unlock_sched(); - + rcu_read_lock(); + ret = percpu_ref_tryget_live_rcu(ref); + rcu_read_unlock(); return ret; } @@ -277,14 +327,14 @@ static inline void percpu_ref_put_many(struct percpu_ref *ref, unsigned long nr) { unsigned long __percpu *percpu_count; - rcu_read_lock_sched(); + rcu_read_lock(); if (__ref_is_percpu(ref, &percpu_count)) this_cpu_sub(*percpu_count, nr); - else if (unlikely(atomic_long_sub_and_test(nr, &ref->count))) - ref->release(ref); + else if (unlikely(atomic_long_sub_and_test(nr, &ref->data->count))) + ref->data->release(ref); - rcu_read_unlock_sched(); + rcu_read_unlock(); } /** @@ -315,21 +365,4 @@ static inline bool percpu_ref_is_dying(struct percpu_ref *ref) return ref->percpu_count_ptr & __PERCPU_REF_DEAD; } -/** - * percpu_ref_is_zero - test whether a percpu refcount reached zero - * @ref: percpu_ref to test - * - * Returns %true if @ref reached zero. - * - * This function is safe to call as long as @ref is between init and exit. - */ -static inline bool percpu_ref_is_zero(struct percpu_ref *ref) -{ - unsigned long __percpu *percpu_count; - - if (__ref_is_percpu(ref, &percpu_count)) - return false; - return !atomic_long_read(&ref->count); -} - #endif |