From 901e3f49facbd31b2b3d1786637b4a35e1022e9b Mon Sep 17 00:00:00 2001 From: Julian Wiedmann Date: Thu, 19 Apr 2018 12:52:07 +0200 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- drivers/s390/net/qeth_core.h | 2 -- drivers/s390/net/qeth_core_main.c | 22 +++++----------------- 2 files changed, 5 insertions(+), 19 deletions(-) diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h index 4326715dc13e..78b98b3e7efa 100644 --- a/drivers/s390/net/qeth_core.h +++ b/drivers/s390/net/qeth_core.h @@ -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; }; /** diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c index 36bc94088de1..5ec47c6ebaa6 100644 --- a/drivers/s390/net/qeth_core_main.c +++ b/drivers/s390/net/qeth_core_main.c @@ -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; -- GitLab