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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
parent9784bd4f1a6ea736ad9bf241f5a965e0a2913a5e (diff)
downloadlinux-8c071b0f19dfa230335d22ce56a8fab5bd20cedc.tar.bz2
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 'drivers')
-rw-r--r--drivers/s390/char/sclp.c4
-rw-r--r--drivers/s390/cio/cio.c4
-rw-r--r--drivers/s390/cio/qdio_main.c10
3 files changed, 9 insertions, 9 deletions
diff --git a/drivers/s390/char/sclp.c b/drivers/s390/char/sclp.c
index a3aa374799dc..1fe264379e0d 100644
--- a/drivers/s390/char/sclp.c
+++ b/drivers/s390/char/sclp.c
@@ -486,7 +486,7 @@ sclp_sync_wait(void)
timeout = 0;
if (timer_pending(&sclp_request_timer)) {
/* Get timeout TOD value */
- timeout = get_tod_clock() +
+ timeout = get_tod_clock_fast() +
sclp_tod_from_jiffies(sclp_request_timer.expires -
jiffies);
}
@@ -508,7 +508,7 @@ sclp_sync_wait(void)
while (sclp_running_state != sclp_running_state_idle) {
/* Check for expired request timer */
if (timer_pending(&sclp_request_timer) &&
- get_tod_clock() > timeout &&
+ get_tod_clock_fast() > timeout &&
del_timer(&sclp_request_timer))
sclp_request_timer.function(sclp_request_timer.data);
cpu_relax();
diff --git a/drivers/s390/cio/cio.c b/drivers/s390/cio/cio.c
index d7da67a31c77..88e35d85d205 100644
--- a/drivers/s390/cio/cio.c
+++ b/drivers/s390/cio/cio.c
@@ -878,9 +878,9 @@ static void css_reset(void)
atomic_inc(&chpid_reset_count);
}
/* Wait for machine check for all channel paths. */
- timeout = get_tod_clock() + (RCHP_TIMEOUT << 12);
+ timeout = get_tod_clock_fast() + (RCHP_TIMEOUT << 12);
while (atomic_read(&chpid_reset_count) != 0) {
- if (get_tod_clock() > timeout)
+ if (get_tod_clock_fast() > timeout)
break;
cpu_relax();
}
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) &&