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percpu_ref: reorganize __percpu_ref_switch_to_atomic() and relocate percpu_ref_switch_to_atomic()

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Reorganize __percpu_ref_switch_to_atomic() so that it looks
structurally similar to __percpu_ref_switch_to_percpu() and relocate
percpu_ref_switch_to_atomic so that the two internal functions are
co-located.

This patch doesn't introduce any functional differences.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2015-09-29 17:47:17 -04:00
parent a2f5630cb7
commit b2302c7fdc
1 changed files with 50 additions and 48 deletions
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98
lib/percpu-refcount.c
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@ -161,28 +161,57 @@ static void percpu_ref_noop_confirm_switch(struct percpu_ref *ref)
static void __percpu_ref_switch_to_atomic(struct percpu_ref *ref,
percpu_ref_func_t *confirm_switch)
{
if (!(ref->percpu_count_ptr & __PERCPU_REF_ATOMIC)) {
/* switching from percpu to atomic */
ref->percpu_count_ptr |= __PERCPU_REF_ATOMIC;
/*
* Non-NULL ->confirm_switch is used to indicate that
* switching is in progress. Use noop one if unspecified.
*/
WARN_ON_ONCE(ref->confirm_switch);
ref->confirm_switch =
confirm_switch ?: percpu_ref_noop_confirm_switch;
percpu_ref_get(ref); /* put after confirmation */
call_rcu_sched(&ref->rcu, percpu_ref_switch_to_atomic_rcu);
} else if (confirm_switch) {
/*
* Somebody else already set ATOMIC. Wait for its
* completion and invoke @confirm_switch() directly.
*/
wait_event(percpu_ref_switch_waitq, !ref->confirm_switch);
confirm_switch(ref);
if (ref->percpu_count_ptr & __PERCPU_REF_ATOMIC) {
if (confirm_switch) {
/*
* Somebody else already set ATOMIC. Wait for its
* completion and invoke @confirm_switch() directly.
*/
wait_event(percpu_ref_switch_waitq, !ref->confirm_switch);
confirm_switch(ref);
}
return;
}
/* switching from percpu to atomic */
ref->percpu_count_ptr |= __PERCPU_REF_ATOMIC;
/*
* Non-NULL ->confirm_switch is used to indicate that switching is
* in progress. Use noop one if unspecified.
*/
WARN_ON_ONCE(ref->confirm_switch);
ref->confirm_switch = confirm_switch ?: percpu_ref_noop_confirm_switch;
percpu_ref_get(ref); /* put after confirmation */
call_rcu_sched(&ref->rcu, percpu_ref_switch_to_atomic_rcu);
}
static void __percpu_ref_switch_to_percpu(struct percpu_ref *ref)
{
unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
int cpu;
BUG_ON(!percpu_count);
if (!(ref->percpu_count_ptr & __PERCPU_REF_ATOMIC))
return;
wait_event(percpu_ref_switch_waitq, !ref->confirm_switch);
atomic_long_add(PERCPU_COUNT_BIAS, &ref->count);
/*
* Restore per-cpu operation. smp_store_release() is paired with
* smp_read_barrier_depends() in __ref_is_percpu() and guarantees
* that the zeroing is visible to all percpu accesses which can see
* the following __PERCPU_REF_ATOMIC clearing.
*/
for_each_possible_cpu(cpu)
*per_cpu_ptr(percpu_count, cpu) = 0;
smp_store_release(&ref->percpu_count_ptr,
ref->percpu_count_ptr & ~__PERCPU_REF_ATOMIC);
}
/**
@ -213,33 +242,6 @@ void percpu_ref_switch_to_atomic(struct percpu_ref *ref,
__percpu_ref_switch_to_atomic(ref, confirm_switch);
}
static void __percpu_ref_switch_to_percpu(struct percpu_ref *ref)
{
unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
int cpu;
BUG_ON(!percpu_count);
if (!(ref->percpu_count_ptr & __PERCPU_REF_ATOMIC))
return;
wait_event(percpu_ref_switch_waitq, !ref->confirm_switch);
atomic_long_add(PERCPU_COUNT_BIAS, &ref->count);
/*
* Restore per-cpu operation. smp_store_release() is paired with
* smp_read_barrier_depends() in __ref_is_percpu() and guarantees
* that the zeroing is visible to all percpu accesses which can see
* the following __PERCPU_REF_ATOMIC clearing.
*/
for_each_possible_cpu(cpu)
*per_cpu_ptr(percpu_count, cpu) = 0;
smp_store_release(&ref->percpu_count_ptr,
ref->percpu_count_ptr & ~__PERCPU_REF_ATOMIC);
}
/**
* percpu_ref_switch_to_percpu - switch a percpu_ref to percpu mode
* @ref: percpu_ref to switch to percpu mode