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Commit 538be0aa authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Jiri Kosina
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HID: intel_ish-hid: clarify locking in client code 



I was trying to understand this code while working on a warning
fix and the locking made no sense: spin_lock_irqsave() is pointless
when run inside of an interrupt handler or nested inside of another
spin_lock_irq() or spin_lock_irqsave().

Here it turned out that the comment above the function is wrong,
as both recv_ishtp_cl_msg_dma() and recv_ishtp_cl_msg() can in fact
be called from a work queue rather than an ISR, so we do have to
use the irqsave() version once.

This fixes the comments accordingly, removes the misleading 'dev_flags'
variable and modifies the inner spinlock to not use 'irqsave'.

No functional change is intended, this is just for readability and
it slightly simplifies the object code.

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent 1260662f

drivers/hid/intel-ish-hid/ishtp/client.c

+17 −26
Original line number Diff line number Diff line
@@ -803,7 +803,7 @@ void ishtp_cl_send_msg(struct ishtp_device *dev, struct ishtp_cl *cl) 
 * @ishtp_hdr: Pointer to message header

 *

 * Receive and dispatch ISHTP client messages. This function executes in ISR

 * context

 * or work queue context

 */

void recv_ishtp_cl_msg(struct ishtp_device *dev,

		       struct ishtp_msg_hdr *ishtp_hdr)
@@ -813,7 +813,6 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, 
	struct ishtp_cl_rb *new_rb;

	unsigned char *buffer = NULL;

	struct ishtp_cl_rb *complete_rb = NULL;

	unsigned long	dev_flags;

	unsigned long	flags;

	int	rb_count;
@@ -828,7 +827,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, 
		goto	eoi;

	}



	spin_lock_irqsave(&dev->read_list_spinlock, dev_flags);

	spin_lock_irqsave(&dev->read_list_spinlock, flags);

	rb_count = -1;

	list_for_each_entry(rb, &dev->read_list.list, list) {

		++rb_count;
@@ -840,8 +839,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, 


		 /* If no Rx buffer is allocated, disband the rb */

		if (rb->buffer.size == 0 || rb->buffer.data == NULL) {

			spin_unlock_irqrestore(&dev->read_list_spinlock,

				dev_flags);

			spin_unlock_irqrestore(&dev->read_list_spinlock, flags);

			dev_err(&cl->device->dev,

				"Rx buffer is not allocated.\n");

			list_del(&rb->list);
@@ -857,8 +855,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, 
		 * back FC, so communication will be stuck anyway)

		 */

		if (rb->buffer.size < ishtp_hdr->length + rb->buf_idx) {

			spin_unlock_irqrestore(&dev->read_list_spinlock,

				dev_flags);

			spin_unlock_irqrestore(&dev->read_list_spinlock, flags);

			dev_err(&cl->device->dev,

				"message overflow. size %d len %d idx %ld\n",

				rb->buffer.size, ishtp_hdr->length,
@@ -884,14 +881,13 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, 
			 * the whole msg arrived, send a new FC, and add a new

			 * rb buffer for the next coming msg

			 */

			spin_lock_irqsave(&cl->free_list_spinlock, flags);

			spin_lock(&cl->free_list_spinlock);



			if (!list_empty(&cl->free_rb_list.list)) {

				new_rb = list_entry(cl->free_rb_list.list.next,

					struct ishtp_cl_rb, list);

				list_del_init(&new_rb->list);

				spin_unlock_irqrestore(&cl->free_list_spinlock,

					flags);

				spin_unlock(&cl->free_list_spinlock);

				new_rb->cl = cl;

				new_rb->buf_idx = 0;

				INIT_LIST_HEAD(&new_rb->list);
@@ -900,8 +896,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, 


				ishtp_hbm_cl_flow_control_req(dev, cl);

			} else {

				spin_unlock_irqrestore(&cl->free_list_spinlock,

					flags);

				spin_unlock(&cl->free_list_spinlock);

			}

		}

		/* One more fragment in message (even if this was last) */
@@ -914,7 +909,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, 
		break;

	}



	spin_unlock_irqrestore(&dev->read_list_spinlock, dev_flags);

	spin_unlock_irqrestore(&dev->read_list_spinlock, flags);

	/* If it's nobody's message, just read and discard it */

	if (!buffer) {

		uint8_t	rd_msg_buf[ISHTP_RD_MSG_BUF_SIZE];
@@ -941,7 +936,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, 
 * @hbm: hbm buffer

 *

 * Receive and dispatch ISHTP client messages using DMA. This function executes

 * in ISR context

 * in ISR or work queue context

 */

void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg,

			   struct dma_xfer_hbm *hbm)
@@ -951,10 +946,10 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, 
	struct ishtp_cl_rb *new_rb;

	unsigned char *buffer = NULL;

	struct ishtp_cl_rb *complete_rb = NULL;

	unsigned long	dev_flags;

	unsigned long	flags;



	spin_lock_irqsave(&dev->read_list_spinlock, dev_flags);

	spin_lock_irqsave(&dev->read_list_spinlock, flags);



	list_for_each_entry(rb, &dev->read_list.list, list) {

		cl = rb->cl;

		if (!cl || !(cl->host_client_id == hbm->host_client_id &&
@@ -966,8 +961,7 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, 
		 * If no Rx buffer is allocated, disband the rb

		 */

		if (rb->buffer.size == 0 || rb->buffer.data == NULL) {

			spin_unlock_irqrestore(&dev->read_list_spinlock,

				dev_flags);

			spin_unlock_irqrestore(&dev->read_list_spinlock, flags);

			dev_err(&cl->device->dev,

				"response buffer is not allocated.\n");

			list_del(&rb->list);
@@ -983,8 +977,7 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, 
		 * back FC, so communication will be stuck anyway)

		 */

		if (rb->buffer.size < hbm->msg_length) {

			spin_unlock_irqrestore(&dev->read_list_spinlock,

				dev_flags);

			spin_unlock_irqrestore(&dev->read_list_spinlock, flags);

			dev_err(&cl->device->dev,

				"message overflow. size %d len %d idx %ld\n",

				rb->buffer.size, hbm->msg_length, rb->buf_idx);
@@ -1008,14 +1001,13 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, 
		 * the whole msg arrived, send a new FC, and add a new

		 * rb buffer for the next coming msg

		 */

		spin_lock_irqsave(&cl->free_list_spinlock, flags);

		spin_lock(&cl->free_list_spinlock);



		if (!list_empty(&cl->free_rb_list.list)) {

			new_rb = list_entry(cl->free_rb_list.list.next,

				struct ishtp_cl_rb, list);

			list_del_init(&new_rb->list);

			spin_unlock_irqrestore(&cl->free_list_spinlock,

				flags);

			spin_unlock(&cl->free_list_spinlock);

			new_rb->cl = cl;

			new_rb->buf_idx = 0;

			INIT_LIST_HEAD(&new_rb->list);
@@ -1024,8 +1016,7 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, 


			ishtp_hbm_cl_flow_control_req(dev, cl);

		} else {

			spin_unlock_irqrestore(&cl->free_list_spinlock,

				flags);

			spin_unlock(&cl->free_list_spinlock);

		}



		/* One more fragment in message (this is always last) */
@@ -1038,7 +1029,7 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, 
		break;

	}



	spin_unlock_irqrestore(&dev->read_list_spinlock, dev_flags);

	spin_unlock_irqrestore(&dev->read_list_spinlock, flags);

	/* If it's nobody's message, just read and discard it */

	if (!buffer) {

		dev_err(dev->devc, "Dropped Rx (DMA) msg - no request\n");