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