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s390/qdio: add sanity checks to the fast-requeue path 

If the device driver were to send out a full queue's worth of SBALs,
current code would end up discovering the last of those SBALs as PRIMED
and erroneously skip the SIGA-w. This immediately stalls the queue.

Add a check to not attempt fast-requeue in this case. While at it also
make sure that the state of the previous SBAL was successfully extracted
before inspecting it.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
alistair/sunxi64-5.4-dsi
Julian Wiedmann 2019-07-11 18:17:36 +02:00 committed by Heiko Carstens
parent 6abe281970
commit a6ec414a4d
1 changed files with 6 additions and 6 deletions
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12
drivers/s390/cio/qdio_main.c
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@ -1558,13 +1558,13 @@ static int handle_outbound(struct qdio_q *q, unsigned int callflags,
rc = qdio_kick_outbound_q(q, phys_aob);
} else if (need_siga_sync(q)) {
rc = qdio_siga_sync_q(q);
} else if (count < QDIO_MAX_BUFFERS_PER_Q &&
get_buf_state(q, prev_buf(bufnr), &state, 0) > 0 &&
state == SLSB_CU_OUTPUT_PRIMED) {
/* The previous buffer is not processed yet, tack on. */
qperf_inc(q, fast_requeue);
} else {
/* try to fast requeue buffers */
get_buf_state(q, prev_buf(bufnr), &state, 0);
if (state != SLSB_CU_OUTPUT_PRIMED)
rc = qdio_kick_outbound_q(q, 0);
else
qperf_inc(q, fast_requeue);
rc = qdio_kick_outbound_q(q, 0);
}
/* in case of SIGA errors we must process the error immediately */