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Date: Wed, 21 May 2008 23:45:41 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Michael Chan <mchan@...adcom.com>
Cc: davem@...emloft.net, michaelc@...wisc.edu, anilgv@...adcom.com,
netdev@...r.kernel.org, linux-scsi@...r.kernel.org,
open-iscsi@...glegroups.com
Subject: Re: [PATCH 1/3] bnx2: Add support for CNIC driver.
On Wed, May 21, 2008 at 06:06:24PM -0700, Michael Chan wrote:
> Add interface for a separate CNIC driver to drive additional rings
> and other resources for iSCSI.
>
> A probe function is exported so that the CNIC driver can get
> information about bnx2 devices. After calling the probe function,
> the CNIC driver can then register with the BNX2 driver before
> initializing the hardware for iSCSI.
Some RCU-related questions interspersed below, for example, how are
updates protected?
Thanx, Paul
> Signed-off-by: Michael Chan <mchan@...adcom.com>
> ---
> drivers/net/bnx2.c | 202 ++++++++++++++++++++++++++++++++++++++++++++++++++--
> drivers/net/bnx2.h | 21 ++++++
> 2 files changed, 218 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/bnx2.c b/drivers/net/bnx2.c
> index b32d227..ba12daf 100644
> --- a/drivers/net/bnx2.c
> +++ b/drivers/net/bnx2.c
> @@ -48,6 +48,11 @@
> #include <linux/cache.h>
> #include <linux/zlib.h>
>
> +#if defined(CONFIG_CNIC) || defined(CONFIG_CNIC_MODULE)
> +#define BCM_CNIC 1
> +#include "cnic_drv.h"
> +#endif
> +
> #include "bnx2.h"
> #include "bnx2_fw.h"
> #include "bnx2_fw2.h"
> @@ -302,6 +307,170 @@ bnx2_ctx_wr(struct bnx2 *bp, u32 cid_addr, u32 offset, u32 val)
> spin_unlock_bh(&bp->indirect_lock);
> }
>
> +#ifdef BCM_CNIC
> +static int
> +bnx2_drv_ctl(struct net_device *dev, struct drv_ctl_info *info)
> +{
> + struct bnx2 *bp = netdev_priv(dev);
> + struct drv_ctl_io *io = &info->data.io;
> +
> + switch (info->cmd) {
> + case DRV_CTL_IO_WR_CMD:
> + bnx2_reg_wr_ind(bp, io->offset, io->data);
> + break;
> + case DRV_CTL_IO_RD_CMD:
> + io->data = bnx2_reg_rd_ind(bp, io->offset);
> + break;
> + case DRV_CTL_CTX_WR_CMD:
> + bnx2_ctx_wr(bp, io->cid_addr, io->offset, io->data);
> + break;
> + default:
> + return -EINVAL;
> + }
> + return 0;
> +}
> +
> +static void bnx2_setup_cnic_irq_info(struct bnx2 *bp)
> +{
> + struct cnic_ops *c_ops;
> + struct cnic_eth_dev *cp = &bp->cnic_eth_dev;
> + struct bnx2_napi *bnapi = &bp->bnx2_napi[0];
> + int sb_id;
> +
> + rcu_read_lock();
> + c_ops = rcu_dereference(bp->cnic_ops);
> + if (!c_ops)
> + goto done;
Given that c_ops is unused below, what is happening here? What prevents
bp->cnic_ops from becoming NULL immediately after we test it? And if
it is OK for bp->cnic_ops to become NULL immediately after we test it,
why are we bothering to test it?
> +
> + if (bp->flags & BNX2_FLAG_USING_MSIX) {
> + cp->drv_state |= CNIC_DRV_STATE_USING_MSIX;
> + bnapi->cnic_present = 0;
> + sb_id = BNX2_CNIC_VEC;
> + cp->irq_arr[0].irq_flags |= CNIC_IRQ_FL_MSIX;
> + } else {
> + cp->drv_state &= ~CNIC_DRV_STATE_USING_MSIX;
> + bnapi->cnic_tag = bnapi->last_status_idx;
> + bnapi->cnic_present = 1;
> + sb_id = 0;
> + cp->irq_arr[0].irq_flags &= !CNIC_IRQ_FL_MSIX;
> + }
> +
> + cp->irq_arr[0].vector = bp->irq_tbl[sb_id].vector;
> + cp->irq_arr[0].status_blk = (void *) ((unsigned long) bp->status_blk +
> + (BNX2_SBLK_MSIX_ALIGN_SIZE * sb_id));
> + cp->irq_arr[0].status_blk_num = sb_id;
> + cp->num_irq = 1;
> +
> +done:
> + rcu_read_unlock();
> +}
> +
> +static int bnx2_register_cnic(struct net_device *dev, struct cnic_ops *ops,
> + void *data)
> +{
> + struct bnx2 *bp = netdev_priv(dev);
> + struct cnic_eth_dev *cp = &bp->cnic_eth_dev;
> +
> + if (ops == NULL)
> + return -EINVAL;
> +
> + if (!try_module_get(ops->cnic_owner))
> + return -EBUSY;
> +
> + bp->cnic_data = data;
> + rcu_assign_pointer(bp->cnic_ops, ops);
What prevents multiple tasks from doing this assignment concurrently?
> +
> + cp->num_irq = 0;
> + cp->drv_state = CNIC_DRV_STATE_REGD;
> +
> + bnx2_setup_cnic_irq_info(bp);
> +
> + return 0;
> +}
> +
> +static int bnx2_unregister_cnic(struct net_device *dev)
> +{
> + struct bnx2 *bp = netdev_priv(dev);
> + struct bnx2_napi *bnapi = &bp->bnx2_napi[0];
> + struct cnic_eth_dev *cp = &bp->cnic_eth_dev;
> +
> + cp->drv_state = 0;
> + module_put(bp->cnic_ops->cnic_owner);
> + bnapi->cnic_present = 0;
> + rcu_assign_pointer(bp->cnic_ops, NULL);
What prevents this from running concurrently with bnx2_register_cnic()?
> + synchronize_rcu();
The caller is responsible for freeing up the old bp->cnic_ops structure?
Or is this structure statically allocated?
If so, is the idea to delay return until all prior calls through the
old ops structure have completed?
> + return 0;
> +}
> +
> +struct cnic_eth_dev *bnx2_cnic_probe(struct net_device *dev)
> +{
> + struct bnx2 *bp = netdev_priv(dev);
> + struct cnic_eth_dev *cp = &bp->cnic_eth_dev;
> +
> + cp->chip_id = bp->chip_id;
> + cp->pdev = bp->pdev;
> + cp->io_base = bp->regview;
> + cp->drv_ctl = bnx2_drv_ctl;
> + cp->drv_register_cnic = bnx2_register_cnic;
> + cp->drv_unregister_cnic = bnx2_unregister_cnic;
> +
> + return cp;
> +}
> +EXPORT_SYMBOL(bnx2_cnic_probe);
> +
> +static void
> +bnx2_cnic_stop(struct bnx2 *bp)
> +{
> + struct cnic_ops *c_ops;
> + struct cnic_ctl_info info;
> +
> + rcu_read_lock();
> + c_ops = rcu_dereference(bp->cnic_ops);
> + if (c_ops) {
> + info.cmd = CNIC_CTL_STOP_CMD;
> + c_ops->cnic_ctl(bp->cnic_data, &info);
> + }
> + rcu_read_unlock();
> +}
> +
> +static void
> +bnx2_cnic_start(struct bnx2 *bp)
> +{
> + struct cnic_ops *c_ops;
> + struct cnic_ctl_info info;
> +
> + rcu_read_lock();
> + c_ops = rcu_dereference(bp->cnic_ops);
> + if (c_ops) {
> + if (!(bp->flags & BNX2_FLAG_USING_MSIX)) {
> + struct bnx2_napi *bnapi = &bp->bnx2_napi[0];
> +
> + bnapi->cnic_tag = bnapi->last_status_idx;
> + }
> + info.cmd = CNIC_CTL_START_CMD;
> + c_ops->cnic_ctl(bp->cnic_data, &info);
> + }
> + rcu_read_unlock();
> +}
> +
> +#else
> +
> +static void bnx2_setup_cnic_irq_info(struct bnx2 *bp)
> +{
> +}
> +
> +static void
> +bnx2_cnic_stop(struct bnx2 *bp)
> +{
> +}
> +
> +static void
> +bnx2_cnic_start(struct bnx2 *bp)
> +{
> +}
> +
> +#endif
> +
> static int
> bnx2_read_phy(struct bnx2 *bp, u32 reg, u32 *val)
> {
> @@ -475,6 +644,7 @@ bnx2_napi_enable(struct bnx2 *bp)
> static void
> bnx2_netif_stop(struct bnx2 *bp)
> {
> + bnx2_cnic_stop(bp);
> bnx2_disable_int_sync(bp);
> if (netif_running(bp->dev)) {
> bnx2_napi_disable(bp);
> @@ -491,6 +661,7 @@ bnx2_netif_start(struct bnx2 *bp)
> netif_wake_queue(bp->dev);
> bnx2_napi_enable(bp);
> bnx2_enable_int(bp);
> + bnx2_cnic_start(bp);
> }
> }
> }
> @@ -3007,6 +3178,9 @@ bnx2_has_work(struct bnx2_napi *bnapi)
> (sblk->status_attn_bits_ack & STATUS_ATTN_EVENTS))
> return 1;
>
> + if (bnapi->cnic_present && (bnapi->cnic_tag != sblk->status_idx))
> + return 1;
> +
> return 0;
> }
>
> @@ -3059,6 +3233,20 @@ static int bnx2_poll_work(struct bnx2 *bp, struct bnx2_napi *bnapi,
> if (bnx2_get_hw_rx_cons(bnapi) != bnapi->rx_cons)
> work_done += bnx2_rx_int(bp, bnapi, budget - work_done);
>
> +#ifdef BCM_CNIC
> + if (bnapi->cnic_present) {
> + struct cnic_ops *c_ops;
> +
> + rcu_read_lock();
> + c_ops = rcu_dereference(bp->cnic_ops);
> + if (c_ops)
> + bnapi->cnic_tag =
> + c_ops->cnic_handler(bp->cnic_data,
> + bnapi->status_blk);
> + rcu_read_unlock();
> + }
> +#endif
> +
> return work_done;
> }
>
> @@ -3100,7 +3288,6 @@ static int bnx2_poll(struct napi_struct *napi, int budget)
> break;
> }
> }
> -
> return work_done;
> }
>
> @@ -5517,19 +5704,19 @@ static void
> bnx2_enable_msix(struct bnx2 *bp)
> {
> int i, rc;
> - struct msix_entry msix_ent[BNX2_MAX_MSIX_VEC];
> + struct msix_entry msix_ent[BNX2_MAX_MSIX_CNIC_VEC];
>
> bnx2_setup_msix_tbl(bp);
> REG_WR(bp, BNX2_PCI_MSIX_CONTROL, BNX2_MAX_MSIX_HW_VEC - 1);
> REG_WR(bp, BNX2_PCI_MSIX_TBL_OFF_BIR, BNX2_PCI_GRC_WINDOW2_BASE);
> REG_WR(bp, BNX2_PCI_MSIX_PBA_OFF_BIT, BNX2_PCI_GRC_WINDOW3_BASE);
>
> - for (i = 0; i < BNX2_MAX_MSIX_VEC; i++) {
> + for (i = 0; i < BNX2_MAX_MSIX_CNIC_VEC; i++) {
> msix_ent[i].entry = i;
> msix_ent[i].vector = 0;
> }
>
> - rc = pci_enable_msix(bp->pdev, msix_ent, BNX2_MAX_MSIX_VEC);
> + rc = pci_enable_msix(bp->pdev, msix_ent, BNX2_MAX_MSIX_CNIC_VEC);
> if (rc != 0)
> return;
>
> @@ -5540,10 +5727,14 @@ bnx2_enable_msix(struct bnx2 *bp)
> strcat(bp->irq_tbl[BNX2_BASE_VEC].name, "-base");
> strcpy(bp->irq_tbl[BNX2_TX_VEC].name, bp->dev->name);
> strcat(bp->irq_tbl[BNX2_TX_VEC].name, "-tx");
> +#ifdef BCM_CNIC
> + strcpy(bp->irq_tbl[BNX2_CNIC_VEC].name, bp->dev->name);
> + strcat(bp->irq_tbl[BNX2_CNIC_VEC].name, "-cnic");
> +#endif
>
> bp->irq_nvecs = BNX2_MAX_MSIX_VEC;
> bp->flags |= BNX2_FLAG_USING_MSIX | BNX2_FLAG_ONE_SHOT_MSI;
> - for (i = 0; i < BNX2_MAX_MSIX_VEC; i++)
> + for (i = 0; i < BNX2_MAX_MSIX_CNIC_VEC; i++)
> bp->irq_tbl[i].vector = msix_ent[i].vector;
> }
>
> @@ -5571,6 +5762,7 @@ bnx2_setup_int_mode(struct bnx2 *bp, int dis_msi)
> bp->irq_tbl[0].vector = bp->pdev->irq;
> }
> }
> + bnx2_setup_cnic_irq_info(bp);
> }
>
> /* Called with rtnl_lock */
> diff --git a/drivers/net/bnx2.h b/drivers/net/bnx2.h
> index 16020a1..a47ee60 100644
> --- a/drivers/net/bnx2.h
> +++ b/drivers/net/bnx2.h
> @@ -6562,6 +6562,15 @@ struct flash_spec {
> #define BNX2_TX_VEC 1
> #define BNX2_TX_INT_NUM (BNX2_TX_VEC << BNX2_PCICFG_INT_ACK_CMD_INT_NUM_SHIFT)
>
> +#ifdef BCM_CNIC
> +#define BNX2_MAX_MSIX_CNIC_VEC (BNX2_MAX_MSIX_VEC + 1)
> +#define BNX2_CNIC_VEC 2
> +#define BNX2_CNIC_INT_NUM \
> + (BNX2_CNIC_VEC << BNX2_PCICFG_INT_ACK_CMD_INT_NUM_SHIFT)
> +#else
> +#define BNX2_MAX_MSIX_CNIC_VEC BNX2_MAX_MSIX_VEC
> +#endif
> +
> struct bnx2_irq {
> irq_handler_t handler;
> u16 vector;
> @@ -6577,6 +6586,9 @@ struct bnx2_napi {
> u32 last_status_idx;
> u32 int_num;
>
> + u32 cnic_tag;
> + int cnic_present;
> +
> u16 tx_cons;
> u16 hw_tx_cons;
>
> @@ -6648,6 +6660,11 @@ struct bnx2 {
> int tx_ring_size;
> u32 tx_wake_thresh;
>
> +#ifdef BCM_CNIC
> + struct cnic_ops *cnic_ops;
> + void *cnic_data;
> +#endif
> +
> /* End of fields used in the performance code paths. */
>
> char *name;
> @@ -6813,6 +6830,10 @@ struct bnx2 {
>
> struct bnx2_irq irq_tbl[BNX2_MAX_MSIX_VEC];
> int irq_nvecs;
> +
> +#ifdef BCM_CNIC
> + struct cnic_eth_dev cnic_eth_dev;
> +#endif
> };
>
> #define REG_RD(bp, offset) \
> --
> 1.5.5.GIT
>
>
>
> --
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