*
* 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()
#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_kill_expedited(struct percpu_ref *ref);
+void percpu_ref_reinit(struct percpu_ref *ref);
/**
* percpu_ref_kill - drop the initial 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;
}
* 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();
}
* 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();
* 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();
*
* 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();
* @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
git.samba.org / sfrench / cifs-2.6.git / blobdiff