> From: linux-acpi-owner@xxxxxxxxxxxxxxx > [mailto:linux-acpi-owner@xxxxxxxxxxxxxxx] 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@xxxxxxxxx> > > Cc: Zhao Yakui <yakui.zhao@xxxxxxxxx> > > Reviewed-by: Huang Ying <ying.huang@xxxxxxxxx> > > --- > > 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@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html ��.n��������+%������w��{.n�����{�����ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
