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linux/drivers/net/mlx4/mcg.c
Eli Cohen 4dc51b3258 IB/mlx4: Fix race when detaching a QP from a multicast group 
When detaching the last QP from an MCG entry, we need to make
sure that at any time, there will be no entry with zero number of
QPs which is linked to the list of the MCGs of the corresponding
hash index.  So don't write back the MCG entry if we are removing the
last QP; just unlink the entry.

Also, remove an unnecessary MCG read when attaching a QP requires
allocation of a new entry in the AMGM.

Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
2008-04-16 21:09:35 -07:00

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/*
* Copyright (c) 2006, 2007 Cisco Systems, Inc. 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/init.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/mlx4/cmd.h>
#include "mlx4.h"
struct mlx4_mgm {
__be32 next_gid_index;
__be32 members_count;
u32 reserved[2];
u8 gid[16];
__be32 qp[MLX4_QP_PER_MGM];
};
static const u8 zero_gid[16]; /* automatically initialized to 0 */
static int mlx4_READ_MCG(struct mlx4_dev *dev, int index,
struct mlx4_cmd_mailbox *mailbox)
{
return mlx4_cmd_box(dev, 0, mailbox->dma, index, 0, MLX4_CMD_READ_MCG,
MLX4_CMD_TIME_CLASS_A);
}
static int mlx4_WRITE_MCG(struct mlx4_dev *dev, int index,
struct mlx4_cmd_mailbox *mailbox)
{
return mlx4_cmd(dev, mailbox->dma, index, 0, MLX4_CMD_WRITE_MCG,
MLX4_CMD_TIME_CLASS_A);
}
static int mlx4_MGID_HASH(struct mlx4_dev *dev, struct mlx4_cmd_mailbox *mailbox,
u16 *hash)
{
u64 imm;
int err;
err = mlx4_cmd_imm(dev, mailbox->dma, &imm, 0, 0, MLX4_CMD_MGID_HASH,
MLX4_CMD_TIME_CLASS_A);
if (!err)
*hash = imm;
return err;
}
/*
* Caller must hold MCG table semaphore. gid and mgm parameters must
* be properly aligned for command interface.
*
* Returns 0 unless a firmware command error occurs.
*
* If GID is found in MGM or MGM is empty, *index = *hash, *prev = -1
* and *mgm holds MGM entry.
*
* if GID is found in AMGM, *index = index in AMGM, *prev = index of
* previous entry in hash chain and *mgm holds AMGM entry.
*
* If no AMGM exists for given gid, *index = -1, *prev = index of last
* entry in hash chain and *mgm holds end of hash chain.
*/
static int find_mgm(struct mlx4_dev *dev,
u8 *gid, struct mlx4_cmd_mailbox *mgm_mailbox,
u16 *hash, int *prev, int *index)
{
struct mlx4_cmd_mailbox *mailbox;
struct mlx4_mgm *mgm = mgm_mailbox->buf;
u8 *mgid;
int err;
mailbox = mlx4_alloc_cmd_mailbox(dev);
if (IS_ERR(mailbox))
return -ENOMEM;
mgid = mailbox->buf;
memcpy(mgid, gid, 16);
err = mlx4_MGID_HASH(dev, mailbox, hash);
mlx4_free_cmd_mailbox(dev, mailbox);
if (err)
return err;
if (0)
mlx4_dbg(dev, "Hash for %04x:%04x:%04x:%04x:"
"%04x:%04x:%04x:%04x is %04x\n",
be16_to_cpu(((__be16 *) gid)[0]),
be16_to_cpu(((__be16 *) gid)[1]),
be16_to_cpu(((__be16 *) gid)[2]),
be16_to_cpu(((__be16 *) gid)[3]),
be16_to_cpu(((__be16 *) gid)[4]),
be16_to_cpu(((__be16 *) gid)[5]),
be16_to_cpu(((__be16 *) gid)[6]),
be16_to_cpu(((__be16 *) gid)[7]),
*hash);
*index = *hash;
*prev = -1;
do {
err = mlx4_READ_MCG(dev, *index, mgm_mailbox);
if (err)
return err;
if (!memcmp(mgm->gid, zero_gid, 16)) {
if (*index != *hash) {
mlx4_err(dev, "Found zero MGID in AMGM.\n");
err = -EINVAL;
}
return err;
}
if (!memcmp(mgm->gid, gid, 16))
return err;
*prev = *index;
*index = be32_to_cpu(mgm->next_gid_index) >> 6;
} while (*index);
*index = -1;
return err;
}
int mlx4_multicast_attach(struct mlx4_dev *dev, struct mlx4_qp *qp, u8 gid[16])
{
struct mlx4_priv *priv = mlx4_priv(dev);
struct mlx4_cmd_mailbox *mailbox;
struct mlx4_mgm *mgm;
u32 members_count;
u16 hash;
int index, prev;
int link = 0;
int i;
int err;
mailbox = mlx4_alloc_cmd_mailbox(dev);
if (IS_ERR(mailbox))
return PTR_ERR(mailbox);
mgm = mailbox->buf;
mutex_lock(&priv->mcg_table.mutex);
err = find_mgm(dev, gid, mailbox, &hash, &prev, &index);
if (err)
goto out;
if (index != -1) {
if (!memcmp(mgm->gid, zero_gid, 16))
memcpy(mgm->gid, gid, 16);
} else {
link = 1;
index = mlx4_bitmap_alloc(&priv->mcg_table.bitmap);
if (index == -1) {
mlx4_err(dev, "No AMGM entries left\n");
err = -ENOMEM;
goto out;
}
index += dev->caps.num_mgms;
memset(mgm, 0, sizeof *mgm);
memcpy(mgm->gid, gid, 16);
}
members_count = be32_to_cpu(mgm->members_count);
if (members_count == MLX4_QP_PER_MGM) {
mlx4_err(dev, "MGM at index %x is full.\n", index);
err = -ENOMEM;
goto out;
}
for (i = 0; i < members_count; ++i)
if (mgm->qp[i] == cpu_to_be32(qp->qpn)) {
mlx4_dbg(dev, "QP %06x already a member of MGM\n", qp->qpn);
err = 0;
goto out;
}
mgm->qp[members_count++] = cpu_to_be32(qp->qpn);
mgm->members_count = cpu_to_be32(members_count);
err = mlx4_WRITE_MCG(dev, index, mailbox);
if (err)
goto out;
if (!link)
goto out;
err = mlx4_READ_MCG(dev, prev, mailbox);
if (err)
goto out;
mgm->next_gid_index = cpu_to_be32(index << 6);
err = mlx4_WRITE_MCG(dev, prev, mailbox);
if (err)
goto out;
out:
if (err && link && index != -1) {
if (index < dev->caps.num_mgms)
mlx4_warn(dev, "Got AMGM index %d < %d",
index, dev->caps.num_mgms);
else
mlx4_bitmap_free(&priv->mcg_table.bitmap,
index - dev->caps.num_mgms);
}
mutex_unlock(&priv->mcg_table.mutex);
mlx4_free_cmd_mailbox(dev, mailbox);
return err;
}
EXPORT_SYMBOL_GPL(mlx4_multicast_attach);
int mlx4_multicast_detach(struct mlx4_dev *dev, struct mlx4_qp *qp, u8 gid[16])
{
struct mlx4_priv *priv = mlx4_priv(dev);
struct mlx4_cmd_mailbox *mailbox;
struct mlx4_mgm *mgm;
u32 members_count;
u16 hash;
int prev, index;
int i, loc;
int err;
mailbox = mlx4_alloc_cmd_mailbox(dev);
if (IS_ERR(mailbox))
return PTR_ERR(mailbox);
mgm = mailbox->buf;
mutex_lock(&priv->mcg_table.mutex);
err = find_mgm(dev, gid, mailbox, &hash, &prev, &index);
if (err)
goto out;
if (index == -1) {
mlx4_err(dev, "MGID %04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x "
"not found\n",
be16_to_cpu(((__be16 *) gid)[0]),
be16_to_cpu(((__be16 *) gid)[1]),
be16_to_cpu(((__be16 *) gid)[2]),
be16_to_cpu(((__be16 *) gid)[3]),
be16_to_cpu(((__be16 *) gid)[4]),
be16_to_cpu(((__be16 *) gid)[5]),
be16_to_cpu(((__be16 *) gid)[6]),
be16_to_cpu(((__be16 *) gid)[7]));
err = -EINVAL;
goto out;
}
members_count = be32_to_cpu(mgm->members_count);
for (loc = -1, i = 0; i < members_count; ++i)
if (mgm->qp[i] == cpu_to_be32(qp->qpn))
loc = i;
if (loc == -1) {
mlx4_err(dev, "QP %06x not found in MGM\n", qp->qpn);
err = -EINVAL;
goto out;
}
mgm->members_count = cpu_to_be32(--members_count);
mgm->qp[loc] = mgm->qp[i - 1];
mgm->qp[i - 1] = 0;
if (i != 1) {
err = mlx4_WRITE_MCG(dev, index, mailbox);
goto out;
}
if (prev == -1) {
/* Remove entry from MGM */
int amgm_index = be32_to_cpu(mgm->next_gid_index) >> 6;
if (amgm_index) {
err = mlx4_READ_MCG(dev, amgm_index, mailbox);
if (err)
goto out;
} else
memset(mgm->gid, 0, 16);
err = mlx4_WRITE_MCG(dev, index, mailbox);
if (err)
goto out;
if (amgm_index) {
if (amgm_index < dev->caps.num_mgms)
mlx4_warn(dev, "MGM entry %d had AMGM index %d < %d",
index, amgm_index, dev->caps.num_mgms);
else
mlx4_bitmap_free(&priv->mcg_table.bitmap,
amgm_index - dev->caps.num_mgms);
}
} else {
/* Remove entry from AMGM */
int cur_next_index = be32_to_cpu(mgm->next_gid_index) >> 6;
err = mlx4_READ_MCG(dev, prev, mailbox);
if (err)
goto out;
mgm->next_gid_index = cpu_to_be32(cur_next_index << 6);
err = mlx4_WRITE_MCG(dev, prev, mailbox);
if (err)
goto out;
if (index < dev->caps.num_mgms)
mlx4_warn(dev, "entry %d had next AMGM index %d < %d",
prev, index, dev->caps.num_mgms);
else
mlx4_bitmap_free(&priv->mcg_table.bitmap,
index - dev->caps.num_mgms);
}
out:
mutex_unlock(&priv->mcg_table.mutex);
mlx4_free_cmd_mailbox(dev, mailbox);
return err;
}
EXPORT_SYMBOL_GPL(mlx4_multicast_detach);
int mlx4_init_mcg_table(struct mlx4_dev *dev)
{
struct mlx4_priv *priv = mlx4_priv(dev);
int err;
err = mlx4_bitmap_init(&priv->mcg_table.bitmap,
dev->caps.num_amgms, dev->caps.num_amgms - 1, 0);
if (err)
return err;
mutex_init(&priv->mcg_table.mutex);
return 0;
}
void mlx4_cleanup_mcg_table(struct mlx4_dev *dev)
{
mlx4_bitmap_cleanup(&mlx4_priv(dev)->mcg_table.bitmap);
}
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