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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2013-10-17 12:38:17 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2013-10-22 09:16:40 +0200
commit8c071b0f19dfa230335d22ce56a8fab5bd20cedc (patch)
treeffd0d6272cd4e3f33b3069b22cb52457030a7f7a /drivers/s390/cio/qdio_main.c
parents390/vmlogrdr: fix array access in vmlogrdr_open() (diff)
downloadlinux-dev-8c071b0f19dfa230335d22ce56a8fab5bd20cedc.tar.xz
linux-dev-8c071b0f19dfa230335d22ce56a8fab5bd20cedc.zip
s390/time: correct use of store clock fast
The result of the store-clock-fast (STCKF) instruction is a bit fuzzy. It can happen that the value stored on one CPU is smaller than the value stored on another CPU, although the order of the stores is the other way around. This can cause deltas of get_tod_clock() values to become negative when they should not be. We need to be more careful with store-clock-fast, this patch partially reverts git commit e4b7b4238e666682555461fa52eecd74652f36bb "time: always use stckf instead of stck if available". The get_tod_clock() function now uses the store-clock-extended (STCKE) instruction. get_tod_clock_fast() can be used if the fuzziness of store-clock-fast is acceptable e.g. for wait loops local to a CPU. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to '')
-rw-r--r--drivers/s390/cio/qdio_main.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c
index 8ed52aa49122..bbd3e511c771 100644
--- a/drivers/s390/cio/qdio_main.c
+++ b/drivers/s390/cio/qdio_main.c
@@ -338,10 +338,10 @@ again:
retries++;
if (!start_time) {
- start_time = get_tod_clock();
+ start_time = get_tod_clock_fast();
goto again;
}
- if ((get_tod_clock() - start_time) < QDIO_BUSY_BIT_PATIENCE)
+ if (get_tod_clock_fast() - start_time < QDIO_BUSY_BIT_PATIENCE)
goto again;
}
if (retries) {
@@ -504,7 +504,7 @@ static int get_inbound_buffer_frontier(struct qdio_q *q)
int count, stop;
unsigned char state = 0;
- q->timestamp = get_tod_clock();
+ q->timestamp = get_tod_clock_fast();
/*
* Don't check 128 buffers, as otherwise qdio_inbound_q_moved
@@ -595,7 +595,7 @@ static inline int qdio_inbound_q_done(struct qdio_q *q)
* At this point we know, that inbound first_to_check
* has (probably) not moved (see qdio_inbound_processing).
*/
- if (get_tod_clock() > q->u.in.timestamp + QDIO_INPUT_THRESHOLD) {
+ if (get_tod_clock_fast() > q->u.in.timestamp + QDIO_INPUT_THRESHOLD) {
DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "in done:%02x",
q->first_to_check);
return 1;
@@ -728,7 +728,7 @@ static int get_outbound_buffer_frontier(struct qdio_q *q)
int count, stop;
unsigned char state = 0;
- q->timestamp = get_tod_clock();
+ q->timestamp = get_tod_clock_fast();
if (need_siga_sync(q))
if (((queue_type(q) != QDIO_IQDIO_QFMT) &&