diff options
Diffstat (limited to 'include/linux/percpu-refcount.h')
| -rw-r--r-- | include/linux/percpu-refcount.h | 123 |
1 files changed, 81 insertions, 42 deletions
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index 3dfbf237cd8f..d5c89e0dd0e6 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() @@ -29,7 +29,7 @@ * calls io_destroy() or the process exits. * * In the aio code, kill_ioctx() is called when we wish to destroy a kioctx; it - * calls percpu_ref_kill(), then hlist_del_rcu() and sychronize_rcu() to remove + * calls percpu_ref_kill(), then hlist_del_rcu() and synchronize_rcu() to remove * the kioctx from the proccess's list of kioctxs - after that, there can't be * any new users of the kioctx (from lookup_ioctx()) and it's then safe to drop * the initial ref with percpu_ref_put(). @@ -49,28 +49,60 @@ #include <linux/kernel.h> #include <linux/percpu.h> #include <linux/rcupdate.h> +#include <linux/gfp.h> struct percpu_ref; typedef void (percpu_ref_func_t)(struct percpu_ref *); +/* flags set in the lower bits of percpu_ref->percpu_count_ptr */ +enum { + __PERCPU_REF_ATOMIC = 1LU << 0, /* operating in atomic mode */ + __PERCPU_REF_DEAD = 1LU << 1, /* (being) killed */ + __PERCPU_REF_ATOMIC_DEAD = __PERCPU_REF_ATOMIC | __PERCPU_REF_DEAD, + + __PERCPU_REF_FLAG_BITS = 2, +}; + +/* @flags for percpu_ref_init() */ +enum { + /* + * Start w/ ref == 1 in atomic mode. Can be switched to percpu + * 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. + */ + 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_INIT_DEAD = 1 << 1, +}; + struct percpu_ref { - atomic_t count; + atomic_long_t count; /* * 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; + percpu_ref_func_t *confirm_switch; + bool force_atomic:1; struct rcu_head rcu; }; int __must_check percpu_ref_init(struct percpu_ref *ref, - percpu_ref_func_t *release); -void percpu_ref_reinit(struct percpu_ref *ref); + percpu_ref_func_t *release, unsigned int flags, + gfp_t gfp); void percpu_ref_exit(struct percpu_ref *ref); +void percpu_ref_switch_to_atomic(struct percpu_ref *ref, + percpu_ref_func_t *confirm_switch); +void percpu_ref_switch_to_percpu(struct percpu_ref *ref); void percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_func_t *confirm_kill); +void percpu_ref_reinit(struct percpu_ref *ref); /** * percpu_ref_kill - drop the initial ref @@ -87,26 +119,24 @@ static inline void percpu_ref_kill(struct percpu_ref *ref) return percpu_ref_kill_and_confirm(ref, NULL); } -#define PCPU_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 __percpu **pcpu_countp) +static inline bool __ref_is_percpu(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_ATOMIC)) return false; - *pcpu_countp = (unsigned __percpu *)pcpu_ptr; + *percpu_countp = (unsigned long __percpu *)percpu_ptr; return true; } @@ -114,18 +144,20 @@ static inline bool __pcpu_ref_alive(struct percpu_ref *ref, * percpu_ref_get - increment a percpu refcount * @ref: percpu_ref to get * - * Analagous to atomic_inc(). - */ + * Analagous to atomic_long_inc(). + * + * This function is safe to call as long as @ref is between init and exit. + */ static inline void percpu_ref_get(struct percpu_ref *ref) { - unsigned __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 (__ref_is_percpu(ref, &percpu_count)) + this_cpu_inc(*percpu_count); else - atomic_inc(&ref->count); + atomic_long_inc(&ref->count); rcu_read_unlock_sched(); } @@ -137,20 +169,20 @@ static inline void percpu_ref_get(struct percpu_ref *ref) * Increment a percpu refcount unless its count already reached zero. * Returns %true on success; %false on failure. * - * The caller is responsible for ensuring that @ref stays accessible. + * 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) { - unsigned __percpu *pcpu_count; - int ret = false; + unsigned long __percpu *percpu_count; + int ret; rcu_read_lock_sched(); - if (__pcpu_ref_alive(ref, &pcpu_count)) { - this_cpu_inc(*pcpu_count); + if (__ref_is_percpu(ref, &percpu_count)) { + this_cpu_inc(*percpu_count); ret = true; } else { - ret = atomic_inc_not_zero(&ref->count); + ret = atomic_long_inc_not_zero(&ref->count); } rcu_read_unlock_sched(); @@ -165,23 +197,26 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref) * Increment a percpu refcount unless it has already been killed. Returns * %true on success; %false on failure. * - * Completion of percpu_ref_kill() in itself doesn't guarantee that tryget - * will fail. For such guarantee, percpu_ref_kill_and_confirm() should be - * used. After the confirm_kill callback is invoked, it's guaranteed that - * no new reference will be given out by percpu_ref_tryget(). + * Completion of percpu_ref_kill() in itself doesn't guarantee that this + * function will fail. For such guarantee, percpu_ref_kill_and_confirm() + * should be used. After the confirm_kill callback is invoked, it's + * guaranteed that no new reference will be given out by + * percpu_ref_tryget_live(). * - * The caller is responsible for ensuring that @ref stays accessible. + * This function is safe to call as long as @ref is between init and exit. */ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref) { - unsigned __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 (__ref_is_percpu(ref, &percpu_count)) { + this_cpu_inc(*percpu_count); ret = true; + } else if (!(ACCESS_ONCE(ref->percpu_count_ptr) & __PERCPU_REF_DEAD)) { + ret = atomic_long_inc_not_zero(&ref->count); } rcu_read_unlock_sched(); @@ -195,16 +230,18 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref) * * Decrement the refcount, and if 0, call the release function (which was passed * to percpu_ref_init()) + * + * This function is safe to call as long as @ref is between init and exit. */ static inline void percpu_ref_put(struct percpu_ref *ref) { - unsigned __percpu *pcpu_count; + unsigned long __percpu *percpu_count; rcu_read_lock_sched(); - if (__pcpu_ref_alive(ref, &pcpu_count)) - this_cpu_dec(*pcpu_count); - else if (unlikely(atomic_dec_and_test(&ref->count))) + if (__ref_is_percpu(ref, &percpu_count)) + this_cpu_dec(*percpu_count); + else if (unlikely(atomic_long_dec_and_test(&ref->count))) ref->release(ref); rcu_read_unlock_sched(); @@ -215,14 +252,16 @@ static inline void percpu_ref_put(struct percpu_ref *ref) * @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 __percpu *pcpu_count; + unsigned long __percpu *percpu_count; - if (__pcpu_ref_alive(ref, &pcpu_count)) + if (__ref_is_percpu(ref, &percpu_count)) return false; - return !atomic_read(&ref->count); + return !atomic_long_read(&ref->count); } #endif |