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/*
* Copyright (c) 2016 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* vlib provides lock-free counters but those
* - Have 16bits per-CPU counter, which may overflow.
* - Would only increment.
*
* This is very similar to vlib counters, but may be used to count reference.
* Such a counter includes an arbitrary number of counters. Each counter
* is identified by its index. This is used to aggregate per-cpu memory.
*
* Warning:
* This reference counter is lock-free but is not race-condition free.
* The counting result is approximate and another mechanism needs to be used
* in order to ensure that an object may be freed.
*
*/
#include <vnet/vnet.h>
/*
* Reference counting
* A specific reference counter is used. The design is quite
* similar to vlib counters but:
* - It is possible to decrease the value
* - Summing will not zero the per-thread counters
* - Only the thread can reallocate its own counters vector (to avoid concurrency issues)
*/
typedef struct {
u32 *counters;
volatile u32 *counter_lock;
CLIB_CACHE_LINE_ALIGN_MARK(o);
} vlib_refcount_per_cpu_t;
typedef struct {
vlib_refcount_per_cpu_t *per_cpu;
} vlib_refcount_t;
static_always_inline
void vlib_refcount_lock (volatile u32 *counter_lock)
{
while (clib_atomic_test_and_set (counter_lock))
;
}
static_always_inline
void vlib_refcount_unlock (volatile u32 *counter_lock)
{
clib_atomic_release(counter_lock);
}
void __vlib_refcount_resize(vlib_refcount_per_cpu_t *per_cpu, u32 size);
static_always_inline
void vlib_refcount_add(vlib_refcount_t *r, u32 thread_index, u32 counter_index, i32 v)
{
vlib_refcount_per_cpu_t *per_cpu = &r->per_cpu[thread_index];
if (PREDICT_FALSE(counter_index >= vec_len(per_cpu->counters)))
__vlib_refcount_resize(per_cpu, clib_max(counter_index + 16,(vec_len(per_cpu->counters)) * 2));
per_cpu->counters[counter_index] += v;
}
u64 vlib_refcount_get(vlib_refcount_t *r, u32 index);
static_always_inline
void vlib_refcount_init(vlib_refcount_t *r)
{
vlib_thread_main_t *tm = vlib_get_thread_main ();
u32 thread_index;
r->per_cpu = 0;
vec_validate (r->per_cpu, tm->n_vlib_mains - 1);
for (thread_index = 0; thread_index < tm->n_vlib_mains; thread_index++)
{
r->per_cpu[thread_index].counter_lock =
clib_mem_alloc_aligned(CLIB_CACHE_LINE_BYTES,CLIB_CACHE_LINE_BYTES);
r->per_cpu[thread_index].counter_lock[0] = 0;
}
}
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