s390/qeth: make queue lock a proper spinlock

queue->state is a ternary spinlock in disguise, used by
OSA's TX completion path to lock the Output Queue and flush any pending
packets on it to the device. If the Queue is already locked by our TX
code, setting the lock word to QETH_OUT_Q_LOCKED_FLUSH lets the TX
completion code move on - the TX path will later take care of things
when it unlocks the Queue.

This sort of DIY locking is a non-starter of course, just let the
TX completion path block on the spinlock when necessary. If that ends up
causing additional latency due to lock contention, then converting
the OSA path to use xmit_more is the right way to go forward.

Also slightly expand the locked section and capture all of
qeth_do_send_packet(), so that the update for the 'bufs_pack' statistics
is done race-free.

While reworking the TX completion path's code, remove a barrier() that
doesn't make any sense.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 7 deletions

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index ecfd6d152e86..00ed58428163 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -420,12 +420,6 @@ struct qeth_qdio_out_buffer {
 
 struct qeth_card;
 
-enum qeth_out_q_states {
-       QETH_OUT_Q_UNLOCKED,
-       QETH_OUT_Q_LOCKED,
-       QETH_OUT_Q_LOCKED_FLUSH,
-};
-
 #define QETH_CARD_STAT_ADD(_c, _stat, _val)	((_c)->stats._stat += (_val))
 #define QETH_CARD_STAT_INC(_c, _stat)		QETH_CARD_STAT_ADD(_c, _stat, 1)
 
@@ -486,12 +480,12 @@ struct qeth_qdio_out_q {
 	struct qeth_qdio_out_buffer *bufs[QDIO_MAX_BUFFERS_PER_Q];
 	struct qdio_outbuf_state *bufstates; /* convenience pointer */
 	struct qeth_out_q_stats stats;
+	spinlock_t lock;
 	u8 next_buf_to_fill;
 	u8 max_elements;
 	u8 queue_no;
 	u8 do_pack;
 	struct qeth_card *card;
-	atomic_t state;
 	/*
 	 * number of buffers that are currently filled (PRIMED)
 	 * -> these buffers are hardware-owned