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Commit 901e3f49 authored by Julian Wiedmann's avatar Julian Wiedmann Committed by David S. Miller
Browse files

s390/qeth: avoid control IO completion stalls 



For control IO, qeth currently tracks the index of the buffer that it
expects to complete the next IO on each qeth_channel. If the channel
presents an IRQ while this buffer has not yet completed, no completion
processing for _any_ completed buffer takes place.
So if the 'next buffer' is skipped for any sort of reason* (eg. when it
is released due to error conditions, before the IO is started), the
buffer obviously won't switch to PROCESSED until it is eventually
allocated for a _different_ IO and completes.
Until this happens, all completion processing on that channel stalls
and pending requests possibly time out.

As a fix, remove the whole 'next buffer' logic and simply process any
IO buffer right when it completes. A channel will never have more than
one IO pending, so there's no risk of processing out-of-sequence.

*Note: currently just one location in the code really handles this problem,
       by advancing the 'next' index manually.

Signed-off-by: default avatarJulian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 686c97ee

drivers/s390/net/qeth_core.h

+0 −2
Original line number Diff line number Diff line
@@ -557,7 +557,6 @@ enum qeth_prot_versions { 
enum qeth_cmd_buffer_state {

	BUF_STATE_FREE,

	BUF_STATE_LOCKED,

	BUF_STATE_PROCESSED,

};



enum qeth_cq {
@@ -601,7 +600,6 @@ struct qeth_channel { 
	struct qeth_cmd_buffer iob[QETH_CMD_BUFFER_NO];

	atomic_t irq_pending;

	int io_buf_no;

	int buf_no;

};



/**

drivers/s390/net/qeth_core_main.c

+5 −17
Original line number Diff line number Diff line
@@ -818,7 +818,6 @@ void qeth_clear_cmd_buffers(struct qeth_channel *channel) 


	for (cnt = 0; cnt < QETH_CMD_BUFFER_NO; cnt++)

		qeth_release_buffer(channel, &channel->iob[cnt]);

	channel->buf_no = 0;

	channel->io_buf_no = 0;

}

EXPORT_SYMBOL_GPL(qeth_clear_cmd_buffers);
@@ -924,7 +923,6 @@ static int qeth_setup_channel(struct qeth_channel *channel) 
			kfree(channel->iob[cnt].data);

		return -ENOMEM;

	}

	channel->buf_no = 0;

	channel->io_buf_no = 0;

	atomic_set(&channel->irq_pending, 0);

	spin_lock_init(&channel->iob_lock);
@@ -1100,11 +1098,9 @@ static void qeth_irq(struct ccw_device *cdev, unsigned long intparm, 
{

	int rc;

	int cstat, dstat;

	struct qeth_cmd_buffer *buffer;

	struct qeth_channel *channel;

	struct qeth_card *card;

	struct qeth_cmd_buffer *iob;

	__u8 index;



	if (__qeth_check_irb_error(cdev, intparm, irb))

		return;
@@ -1182,25 +1178,18 @@ static void qeth_irq(struct ccw_device *cdev, unsigned long intparm, 
		channel->state = CH_STATE_RCD_DONE;

		goto out;

	}

	if (intparm) {

		buffer = (struct qeth_cmd_buffer *) __va((addr_t)intparm);

		buffer->state = BUF_STATE_PROCESSED;

	}

	if (channel == &card->data)

		return;

	if (channel == &card->read &&

	    channel->state == CH_STATE_UP)

		__qeth_issue_next_read(card);



	iob = channel->iob;

	index = channel->buf_no;

	while (iob[index].state == BUF_STATE_PROCESSED) {

		if (iob[index].callback != NULL)

			iob[index].callback(channel, iob + index);



		index = (index + 1) % QETH_CMD_BUFFER_NO;

	if (intparm) {

		iob = (struct qeth_cmd_buffer *) __va((addr_t)intparm);

		if (iob->callback)

			iob->callback(iob->channel, iob);

	}

	channel->buf_no = index;



out:

	wake_up(&card->wait_q);

	return;
@@ -2214,7 +2203,6 @@ int qeth_send_control_data(struct qeth_card *card, int len, 
error:

	atomic_set(&card->write.irq_pending, 0);

	qeth_release_buffer(iob->channel, iob);

	card->write.buf_no = (card->write.buf_no + 1) % QETH_CMD_BUFFER_NO;

	rc = reply->rc;

	qeth_put_reply(reply);

	return rc;