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/*
* Copyright (c) 2006 Oracle. All rights reserved.
*
* This software is available to you under a choice of one of two
* licenses. You may choose to be licensed under the terms of the GNU
* General Public License (GPL) Version 2, available from the file
* COPYING in the main directory of this source tree, or the
* OpenIB.org BSD license below:
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above
* copyright notice, this list of conditions and the following
* disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
*/
#include <linux/kernel.h>
#include "rds.h"
#include "ib.h"
/*
* Locking for IB rings.
* We assume that allocation is always protected by a mutex
* in the caller (this is a valid assumption for the current
* implementation).
*
* Freeing always happens in an interrupt, and hence only
* races with allocations, but not with other free()s.
*
* The interaction between allocation and freeing is that
* the alloc code has to determine the number of free entries.
* To this end, we maintain two counters; an allocation counter
* and a free counter. Both are allowed to run freely, and wrap
* around.
* The number of used entries is always (alloc_ctr - free_ctr) % NR.
*
* The current implementation makes free_ctr atomic. When the
* caller finds an allocation fails, it should set an "alloc fail"
* bit and retry the allocation. The "alloc fail" bit essentially tells
* the CQ completion handlers to wake it up after freeing some
* more entries.
*/
/*
* This only happens on shutdown.
*/
DECLARE_WAIT_QUEUE_HEAD(rds_ib_ring_empty_wait);
void rds_ib_ring_init(struct rds_ib_work_ring *ring, u32 nr)
{
memset(ring, 0, sizeof(*ring));
ring->w_nr = nr;
rdsdebug("ring %p nr %u\n", ring, ring->w_nr);
}
static inline u32 __rds_ib_ring_used(struct rds_ib_work_ring *ring)
{
u32 diff;
/* This assumes that atomic_t has at least as many bits as u32 */
diff = ring->w_alloc_ctr - (u32) atomic_read(&ring->w_free_ctr);
BUG_ON(diff > ring->w_nr);
return diff;
}
void rds_ib_ring_resize(struct rds_ib_work_ring *ring, u32 nr)
{
/* We only ever get called from the connection setup code,
* prior to creating the QP. */
BUG_ON(__rds_ib_ring_used(ring));
ring->w_nr = nr;
}
static int __rds_ib_ring_empty(struct rds_ib_work_ring *ring)
{
return __rds_ib_ring_used(ring) == 0;
}
u32 rds_ib_ring_alloc(struct rds_ib_work_ring *ring, u32 val, u32 *pos)
{
u32 ret = 0, avail;
avail = ring->w_nr - __rds_ib_ring_used(ring);
rdsdebug("ring %p val %u next %u free %u\n", ring, val,
ring->w_alloc_ptr, avail);
if (val && avail) {
ret = min(val, avail);
*pos = ring->w_alloc_ptr;
ring->w_alloc_ptr = (ring->w_alloc_ptr + ret) % ring->w_nr;
ring->w_alloc_ctr += ret;
}
return ret;
}
void rds_ib_ring_free(struct rds_ib_work_ring *ring, u32 val)
{
ring->w_free_ptr = (ring->w_free_ptr + val) % ring->w_nr;
atomic_add(val, &ring->w_free_ctr);
if (__rds_ib_ring_empty(ring) &&
waitqueue_active(&rds_ib_ring_empty_wait))
wake_up(&rds_ib_ring_empty_wait);
}
void rds_ib_ring_unalloc(struct rds_ib_work_ring *ring, u32 val)
{
ring->w_alloc_ptr = (ring->w_alloc_ptr - val) % ring->w_nr;
ring->w_alloc_ctr -= val;
}
int rds_ib_ring_empty(struct rds_ib_work_ring *ring)
{
return __rds_ib_ring_empty(ring);
}
int rds_ib_ring_low(struct rds_ib_work_ring *ring)
{
return __rds_ib_ring_used(ring) <= (ring->w_nr >> 1);
}
/*
* returns the oldest alloced ring entry. This will be the next one
* freed. This can't be called if there are none allocated.
*/
u32 rds_ib_ring_oldest(struct rds_ib_work_ring *ring)
{
return ring->w_free_ptr;
}
/*
* returns the number of completed work requests.
*/
u32 rds_ib_ring_completed(struct rds_ib_work_ring *ring, u32 wr_id, u32 oldest)
{
u32 ret;
if (oldest <= (unsigned long long)wr_id)
ret = (unsigned long long)wr_id - oldest + 1;
else
ret = ring->w_nr - oldest + (unsigned long long)wr_id + 1;
rdsdebug("ring %p ret %u wr_id %u oldest %u\n", ring, ret,
wr_id, oldest);
return ret;
}
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