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: Julian Wiedmann <jwi@linux.vnet.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -557,7 +557,6 @@ enum qeth_prot_versions {
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enum qeth_cmd_buffer_state {
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BUF_STATE_FREE,
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BUF_STATE_LOCKED,
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BUF_STATE_PROCESSED,
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};
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enum qeth_cq {
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@ -601,7 +600,6 @@ struct qeth_channel {
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struct qeth_cmd_buffer iob[QETH_CMD_BUFFER_NO];
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atomic_t irq_pending;
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int io_buf_no;
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int buf_no;
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};
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/**
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@ -818,7 +818,6 @@ void qeth_clear_cmd_buffers(struct qeth_channel *channel)
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for (cnt = 0; cnt < QETH_CMD_BUFFER_NO; cnt++)
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qeth_release_buffer(channel, &channel->iob[cnt]);
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channel->buf_no = 0;
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channel->io_buf_no = 0;
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}
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EXPORT_SYMBOL_GPL(qeth_clear_cmd_buffers);
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@ -924,7 +923,6 @@ static int qeth_setup_channel(struct qeth_channel *channel)
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kfree(channel->iob[cnt].data);
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return -ENOMEM;
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}
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channel->buf_no = 0;
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channel->io_buf_no = 0;
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atomic_set(&channel->irq_pending, 0);
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spin_lock_init(&channel->iob_lock);
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@ -1100,11 +1098,9 @@ static void qeth_irq(struct ccw_device *cdev, unsigned long intparm,
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{
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int rc;
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int cstat, dstat;
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struct qeth_cmd_buffer *buffer;
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struct qeth_channel *channel;
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struct qeth_card *card;
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struct qeth_cmd_buffer *iob;
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__u8 index;
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if (__qeth_check_irb_error(cdev, intparm, irb))
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return;
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@ -1182,25 +1178,18 @@ static void qeth_irq(struct ccw_device *cdev, unsigned long intparm,
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channel->state = CH_STATE_RCD_DONE;
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goto out;
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}
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if (intparm) {
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buffer = (struct qeth_cmd_buffer *) __va((addr_t)intparm);
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buffer->state = BUF_STATE_PROCESSED;
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}
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if (channel == &card->data)
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return;
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if (channel == &card->read &&
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channel->state == CH_STATE_UP)
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__qeth_issue_next_read(card);
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iob = channel->iob;
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index = channel->buf_no;
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while (iob[index].state == BUF_STATE_PROCESSED) {
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if (iob[index].callback != NULL)
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iob[index].callback(channel, iob + index);
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index = (index + 1) % QETH_CMD_BUFFER_NO;
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if (intparm) {
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iob = (struct qeth_cmd_buffer *) __va((addr_t)intparm);
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if (iob->callback)
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iob->callback(iob->channel, iob);
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}
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channel->buf_no = index;
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out:
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wake_up(&card->wait_q);
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return;
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@ -2214,7 +2203,6 @@ time_err:
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error:
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atomic_set(&card->write.irq_pending, 0);
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qeth_release_buffer(iob->channel, iob);
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card->write.buf_no = (card->write.buf_no + 1) % QETH_CMD_BUFFER_NO;
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rc = reply->rc;
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qeth_put_reply(reply);
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return rc;
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