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Commit 7b984477 authored by Lv Zheng's avatar Lv Zheng Committed by Rafael J. Wysocki
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ACPI / IPMI: Add reference counting for ACPI IPMI transfers 



This patch adds reference counting for ACPI IPMI transfers to tune the
locking granularity of tx_msg_lock.

This patch also makes the whole acpi_ipmi module's coding style consistent
by using reference counting for all its objects (i.e., acpi_ipmi_device and
acpi_ipmi_msg).

The acpi_ipmi_msg handling is re-designed using referece counting.
 1. tx_msg is always unlinked before complete(), so that it is safe to put
    complete() out side of tx_msg_lock.
 2. tx_msg reference counters are incremented before calling
    ipmi_request_settime() and tx_msg_lock protection is added to
    ipmi_cancel_tx_msg() so that a complete() can be safely called in
    parellel with tx_msg unlinking in failure cases.
 3. tx_msg holds a reference to 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: default avatarLv Zheng <lv.zheng@intel.com>
Reviewed-by: default avatarHuang Ying <ying.huang@intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent e96a94ed

drivers/acpi/acpi_ipmi.c

+85 −32
Original line number Diff line number Diff line
@@ -104,6 +104,7 @@ struct acpi_ipmi_msg { 
	u8	data[ACPI_IPMI_MAX_MSG_LENGTH];

	u8	rx_len;

	struct acpi_ipmi_device *device;

	struct kref	kref;

};



/* IPMI request/response buffer per ACPI 4.0, sec 5.5.2.4.3.2 */
@@ -208,16 +209,20 @@ static void acpi_ipmi_dev_put(struct acpi_ipmi_device *ipmi_device) 
	kref_put(&ipmi_device->kref, ipmi_dev_release_kref);

}



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_dev_get();

	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");

		acpi_ipmi_dev_put(ipmi);

		return NULL;

	}

	kref_init(&ipmi_msg->kref);

	init_completion(&ipmi_msg->tx_complete);

	INIT_LIST_HEAD(&ipmi_msg->head);

	ipmi_msg->device = ipmi;
@@ -225,6 +230,32 @@ static struct acpi_ipmi_msg *acpi_alloc_ipmi_msg(struct acpi_ipmi_device *ipmi) 
	return ipmi_msg;

}



static void ipmi_msg_release(struct acpi_ipmi_msg *tx_msg)

{

	acpi_ipmi_dev_put(tx_msg->device);

	kfree(tx_msg);

}



static void ipmi_msg_release_kref(struct kref *kref)

{

	struct acpi_ipmi_msg *tx_msg =

		container_of(kref, struct acpi_ipmi_msg, kref);



	ipmi_msg_release(tx_msg);

}



static struct acpi_ipmi_msg *acpi_ipmi_msg_get(struct acpi_ipmi_msg *tx_msg)

{

	kref_get(&tx_msg->kref);



	return tx_msg;

}



static void acpi_ipmi_msg_put(struct acpi_ipmi_msg *tx_msg)

{

	kref_put(&tx_msg->kref, ipmi_msg_release_kref);

}



#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,
@@ -305,7 +336,7 @@ 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;



	/*
@@ -317,18 +348,47 @@ static void ipmi_flush_tx_msg(struct acpi_ipmi_device *ipmi) 
	 * ipmi_recv_msg(s) are freed after invoking ipmi_destroy_user().

	 */

	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);

}



static void ipmi_cancel_tx_msg(struct acpi_ipmi_device *ipmi,

			       struct acpi_ipmi_msg *msg)

{

	struct acpi_ipmi_msg *tx_msg, *temp;

	bool msg_found = false;

	unsigned long flags;



	spin_lock_irqsave(&ipmi->tx_msg_lock, flags);

	list_for_each_entry_safe(tx_msg, temp, &ipmi->tx_msg_list, head) {

		if (msg == tx_msg) {

			msg_found = true;

			list_del(&tx_msg->head);

			break;

		}

	}

	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;

	int msg_found = 0;

	struct acpi_ipmi_msg *tx_msg;

	bool msg_found = false;

	struct acpi_ipmi_msg *tx_msg, *temp;

	struct pnp_dev *pnp_dev = ipmi_device->pnp_dev;

	unsigned long flags;
@@ -339,17 +399,19 @@ static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data) 
		goto out_msg;

	}

	spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);

	list_for_each_entry(tx_msg, &ipmi_device->tx_msg_list, head) {

	list_for_each_entry_safe(tx_msg, temp, &ipmi_device->tx_msg_list, head) {

		if (msg->msgid == tx_msg->tx_msgid) {

			msg_found = 1;

			msg_found = true;

			list_del(&tx_msg->head);

			break;

		}

	}

	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 */
@@ -375,8 +437,7 @@ static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data) 
	tx_msg->msg_done = ACPI_IPMI_OK;

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);

};
@@ -491,26 +552,23 @@ acpi_ipmi_space_handler(u32 function, acpi_physical_address address, 
	if ((function & ACPI_IO_MASK) == ACPI_READ)

		return AE_TYPE;



	ipmi_device = acpi_ipmi_dev_get();

	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);

	mutex_lock(&driver_data.ipmi_lock);

	/* Do not add a tx_msg that can not be flushed. */

	if (ipmi_device->dead) {

		status = AE_NOT_EXIST;

		mutex_unlock(&driver_data.ipmi_lock);

		goto out_msg;

		ipmi_msg_release(tx_msg);

		return AE_NOT_EXIST;

	}

	spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);

	list_add_tail(&tx_msg->head, &ipmi_device->tx_msg_list);
@@ -523,20 +581,15 @@ acpi_ipmi_space_handler(u32 function, acpi_physical_address address, 
					NULL, 0, 0, IPMI_TIMEOUT);

	if (err) {

		status = AE_ERROR;

		goto out_list;

		goto out_msg;

	}

	wait_for_completion(&tx_msg->tx_complete);

	acpi_format_ipmi_response(tx_msg, value);

	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;

}