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    SubjectRE: [PATCH 07/13] ACPI/IPMI: Add reference counting for ACPI IPMI transfers
    Date
    > From: linux-acpi-owner@vger.kernel.org
    > [mailto:linux-acpi-owner@vger.kernel.org] On Behalf Of Rafael J. Wysocki
    > Sent: Friday, July 26, 2013 6:23 AM
    >
    > On Tuesday, July 23, 2013 04:09:54 PM Lv Zheng wrote:
    > > This patch adds reference counting for ACPI IPMI transfers to tune the
    > > locking granularity of tx_msg_lock.
    > >
    > > The acpi_ipmi_msg handling is re-designed using referece counting.
    > > 1. tx_msg is always unlinked before complete(), so that:
    > > 1.1. it is safe to put complete() out side of tx_msg_lock;
    > > 1.2. complete() can only happen once, thus smp_wmb() is not required.
    > > 2. Increasing the reference of tx_msg before calling
    > > ipmi_request_settime() and introducing tx_msg_lock protected
    > > ipmi_cancel_tx_msg() so that a complete() can happen in parellel with
    > > tx_msg unlinking in the failure cases.
    > > 3. tx_msg holds the reference of acpi_ipmi_device so that it can be flushed
    > > and freed in the contexts other than acpi_ipmi_space_handler().
    > >
    > > The lockdep_chains shows all acpi_ipmi locks are leaf locks after the
    > > tuning:
    > > 1. ipmi_lock is always leaf:
    > > irq_context: 0
    > > [ffffffff81a943f8] smi_watchers_mutex
    > > [ffffffffa06eca60] driver_data.ipmi_lock
    > > irq_context: 0
    > > [ffffffff82767b40] &buffer->mutex
    > > [ffffffffa00a6678] s_active#103
    > > [ffffffffa06eca60] driver_data.ipmi_lock
    > > 2. without this patch applied, lock used by complete() is held after
    > > holding tx_msg_lock:
    > > irq_context: 0
    > > [ffffffff82767b40] &buffer->mutex
    > > [ffffffffa00a6678] s_active#103
    > > [ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
    > > irq_context: 1
    > > [ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
    > > irq_context: 1
    > > [ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
    > > [ffffffffa06eccf0] &x->wait#25
    > > irq_context: 1
    > > [ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
    > > [ffffffffa06eccf0] &x->wait#25
    > > [ffffffff81e36620] &p->pi_lock
    > > irq_context: 1
    > > [ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
    > > [ffffffffa06eccf0] &x->wait#25
    > > [ffffffff81e36620] &p->pi_lock
    > > [ffffffff81e5d0a8] &rq->lock
    > > 3. with this patch applied, tx_msg_lock is always leaf:
    > > irq_context: 0
    > > [ffffffff82767b40] &buffer->mutex
    > > [ffffffffa00a66d8] s_active#107
    > > [ffffffffa07ecdc8] &(&ipmi_device->tx_msg_lock)->rlock
    > > irq_context: 1
    > > [ffffffffa07ecdc8] &(&ipmi_device->tx_msg_lock)->rlock
    > >
    > > Signed-off-by: Lv Zheng <lv.zheng@intel.com>
    > > Cc: Zhao Yakui <yakui.zhao@intel.com>
    > > Reviewed-by: Huang Ying <ying.huang@intel.com>
    > > ---
    > > drivers/acpi/acpi_ipmi.c | 107
    > +++++++++++++++++++++++++++++++++-------------
    > > 1 file changed, 77 insertions(+), 30 deletions(-)
    > >
    > > diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
    > > index 2a09156..0ee1ea6 100644
    > > --- a/drivers/acpi/acpi_ipmi.c
    > > +++ b/drivers/acpi/acpi_ipmi.c
    > > @@ -105,6 +105,7 @@ struct acpi_ipmi_msg {
    > > u8 data[ACPI_IPMI_MAX_MSG_LENGTH];
    > > u8 rx_len;
    > > struct acpi_ipmi_device *device;
    > > + atomic_t refcnt;
    >
    > Again: kref, please?

    Please see the concerns in another email.

    >
    > > };
    > >
    > > /* IPMI request/response buffer per ACPI 4.0, sec 5.5.2.4.3.2 */
    > > @@ -195,22 +196,47 @@ static struct acpi_ipmi_device
    > *acpi_ipmi_get_selected_smi(void)
    > > return ipmi_device;
    > > }
    > >
    > > -static struct acpi_ipmi_msg *acpi_alloc_ipmi_msg(struct acpi_ipmi_device
    > *ipmi)
    > > +static struct acpi_ipmi_msg *ipmi_msg_alloc(void)
    > > {
    > > + struct acpi_ipmi_device *ipmi;
    > > struct acpi_ipmi_msg *ipmi_msg;
    > > - struct pnp_dev *pnp_dev = ipmi->pnp_dev;
    > >
    > > + ipmi = acpi_ipmi_get_selected_smi();
    > > + if (!ipmi)
    > > + return NULL;
    > > ipmi_msg = kzalloc(sizeof(struct acpi_ipmi_msg), GFP_KERNEL);
    > > - if (!ipmi_msg) {
    > > - dev_warn(&pnp_dev->dev, "Can't allocate memory for ipmi_msg\n");
    > > + if (!ipmi_msg) {
    > > + acpi_ipmi_dev_put(ipmi);
    > > return NULL;
    > > }
    > > + atomic_set(&ipmi_msg->refcnt, 1);
    > > init_completion(&ipmi_msg->tx_complete);
    > > INIT_LIST_HEAD(&ipmi_msg->head);
    > > ipmi_msg->device = ipmi;
    > > +
    > > return ipmi_msg;
    > > }
    > >
    > > +static struct acpi_ipmi_msg *
    > > +acpi_ipmi_msg_get(struct acpi_ipmi_msg *tx_msg)
    > > +{
    > > + if (tx_msg)
    > > + atomic_inc(&tx_msg->refcnt);
    > > + return tx_msg;
    > > +}
    > > +
    > > +static void ipmi_msg_release(struct acpi_ipmi_msg *tx_msg)
    > > +{
    > > + acpi_ipmi_dev_put(tx_msg->device);
    > > + kfree(tx_msg);
    > > +}
    > > +
    > > +static void acpi_ipmi_msg_put(struct acpi_ipmi_msg *tx_msg)
    > > +{
    > > + if (tx_msg && atomic_dec_and_test(&tx_msg->refcnt))
    > > + ipmi_msg_release(tx_msg);
    > > +}
    > > +
    > > #define IPMI_OP_RGN_NETFN(offset) ((offset >> 8) & 0xff)
    > > #define IPMI_OP_RGN_CMD(offset) (offset & 0xff)
    > > static int acpi_format_ipmi_request(struct acpi_ipmi_msg *tx_msg,
    > > @@ -300,7 +326,7 @@ static void acpi_format_ipmi_response(struct
    > acpi_ipmi_msg *msg,
    > >
    > > static void ipmi_flush_tx_msg(struct acpi_ipmi_device *ipmi)
    > > {
    > > - struct acpi_ipmi_msg *tx_msg, *temp;
    > > + struct acpi_ipmi_msg *tx_msg;
    > > unsigned long flags;
    > >
    > > /*
    > > @@ -311,16 +337,46 @@ static void ipmi_flush_tx_msg(struct
    > acpi_ipmi_device *ipmi)
    > > */
    > > while (atomic_read(&ipmi->refcnt) > 1) {
    > > spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
    > > - list_for_each_entry_safe(tx_msg, temp,
    > > - &ipmi->tx_msg_list, head) {
    > > + while (!list_empty(&ipmi->tx_msg_list)) {
    > > + tx_msg = list_first_entry(&ipmi->tx_msg_list,
    > > + struct acpi_ipmi_msg,
    > > + head);
    > > + list_del(&tx_msg->head);
    > > + spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
    > > +
    > > /* wake up the sleep thread on the Tx msg */
    > > complete(&tx_msg->tx_complete);
    > > + acpi_ipmi_msg_put(tx_msg);
    > > + spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
    > > }
    > > spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
    > > +
    > > schedule_timeout_uninterruptible(msecs_to_jiffies(1));
    > > }
    > > }
    > >
    > > +static void ipmi_cancel_tx_msg(struct acpi_ipmi_device *ipmi,
    > > + struct acpi_ipmi_msg *msg)
    > > +{
    > > + struct acpi_ipmi_msg *tx_msg;
    > > + int msg_found = 0;
    >
    > Use bool?

    OK.
    There are other int flags in the original codes, do I need to do a cleanup for all of them (dev_found)?

    >
    > > + unsigned long flags;
    > > +
    > > + spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
    > > + list_for_each_entry(tx_msg, &ipmi->tx_msg_list, head) {
    > > + if (msg == tx_msg) {
    > > + msg_found = 1;
    > > + break;
    > > + }
    > > + }
    > > + if (msg_found)
    > > + list_del(&tx_msg->head);
    >
    > The list_del() can be done when you set msg_found.

    Please see my concerns in another email.

    Thanks and best regards
    -Lv

    >
    > > + spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
    > > +
    > > + if (msg_found)
    > > + acpi_ipmi_msg_put(tx_msg);
    > > +}
    > > +
    > > static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void
    > *user_msg_data)
    > > {
    > > struct acpi_ipmi_device *ipmi_device = user_msg_data;
    > > @@ -343,12 +399,15 @@ static void ipmi_msg_handler(struct
    > ipmi_recv_msg *msg, void *user_msg_data)
    > > break;
    > > }
    > > }
    > > + if (msg_found)
    > > + list_del(&tx_msg->head);
    > > + spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
    > >
    > > if (!msg_found) {
    > > dev_warn(&pnp_dev->dev,
    > > "Unexpected response (msg id %ld) is returned.\n",
    > > msg->msgid);
    > > - goto out_lock;
    > > + goto out_msg;
    > > }
    > >
    > > /* copy the response data to Rx_data buffer */
    > > @@ -360,14 +419,11 @@ static void ipmi_msg_handler(struct
    > ipmi_recv_msg *msg, void *user_msg_data)
    > > }
    > > tx_msg->rx_len = msg->msg.data_len;
    > > memcpy(tx_msg->data, msg->msg.data, tx_msg->rx_len);
    > > - /* tx_msg content must be valid before setting msg_done flag */
    > > - smp_wmb();
    > > tx_msg->msg_done = 1;
    > >
    > > out_comp:
    > > complete(&tx_msg->tx_complete);
    > > -out_lock:
    > > - spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
    > > + acpi_ipmi_msg_put(tx_msg);
    > > out_msg:
    > > ipmi_free_recv_msg(msg);
    > > }
    > > @@ -493,21 +549,17 @@ acpi_ipmi_space_handler(u32 function,
    > acpi_physical_address address,
    > > if ((function & ACPI_IO_MASK) == ACPI_READ)
    > > return AE_TYPE;
    > >
    > > - ipmi_device = acpi_ipmi_get_selected_smi();
    > > - if (!ipmi_device)
    > > + tx_msg = ipmi_msg_alloc();
    > > + if (!tx_msg)
    > > return AE_NOT_EXIST;
    > > -
    > > - tx_msg = acpi_alloc_ipmi_msg(ipmi_device);
    > > - if (!tx_msg) {
    > > - status = AE_NO_MEMORY;
    > > - goto out_ref;
    > > - }
    > > + ipmi_device = tx_msg->device;
    > >
    > > if (acpi_format_ipmi_request(tx_msg, address, value) != 0) {
    > > - status = AE_TYPE;
    > > - goto out_msg;
    > > + ipmi_msg_release(tx_msg);
    > > + return AE_TYPE;
    > > }
    > >
    > > + acpi_ipmi_msg_get(tx_msg);
    > > spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);
    > > list_add_tail(&tx_msg->head, &ipmi_device->tx_msg_list);
    > > spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
    > > @@ -518,21 +570,16 @@ acpi_ipmi_space_handler(u32 function,
    > acpi_physical_address address,
    > > NULL, 0, 0, 0);
    > > if (err) {
    > > status = AE_ERROR;
    > > - goto out_list;
    > > + goto out_msg;
    > > }
    > > rem_time = wait_for_completion_timeout(&tx_msg->tx_complete,
    > > IPMI_TIMEOUT);
    > > acpi_format_ipmi_response(tx_msg, value, rem_time);
    > > status = AE_OK;
    > >
    > > -out_list:
    > > - spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);
    > > - list_del(&tx_msg->head);
    > > - spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
    > > out_msg:
    > > - kfree(tx_msg);
    > > -out_ref:
    > > - acpi_ipmi_dev_put(ipmi_device);
    > > + ipmi_cancel_tx_msg(ipmi_device, tx_msg);
    > > + acpi_ipmi_msg_put(tx_msg);
    > > return status;
    > > }
    > >
    > >
    > --
    > I speak only for myself.
    > Rafael J. Wysocki, Intel Open Source Technology Center.
    > --
    > To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
    > the body of a message to majordomo@vger.kernel.org
    > More majordomo info at http://vger.kernel.org/majordomo-info.html
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