From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
The clock sync mode flag CLOCK_SYNC_STP is not cleared when stp
is set offline. In this case the get_sync_clock() function returns
-EACCESS and the dasd driver will block all i/o until stp is enabled
again. In addition get_sync_clock can return -EACCESS if the clock is
not in sync instead of -EAGAIN.
Rework the stp/etr online handling to fix these problems.
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---
arch/s390/kernel/time.c | 71 +++++++++++++++++++++++++++++-------------------
1 file changed, 44 insertions(+), 27 deletions(-)
Index: quilt-2.6/arch/s390/kernel/time.c
===================================================================
--- quilt-2.6.orig/arch/s390/kernel/time.c
+++ quilt-2.6/arch/s390/kernel/time.c
@@ -331,6 +331,7 @@ static unsigned long long adjust_time(un
}
static DEFINE_PER_CPU(atomic_t, clock_sync_word);
+static DEFINE_MUTEX(clock_sync_mutex);
static unsigned long clock_sync_flags;
#define CLOCK_SYNC_HAS_ETR 0
@@ -394,6 +395,20 @@ static void enable_sync_clock(void)
atomic_set_mask(0x80000000, sw_ptr);
}
+/*
+ * Function to check if the clock is in sync.
+ */
+static inline int check_sync_clock(void)
+{
+ atomic_t *sw_ptr;
+ int rc;
+
+ sw_ptr = &get_cpu_var(clock_sync_word);
+ rc = (atomic_read(sw_ptr) & 0x80000000U) != 0;
+ put_cpu_var(clock_sync_sync);
+ return rc;
+}
+
/* Single threaded workqueue used for etr and stp sync events */
static struct workqueue_struct *time_sync_wq;
@@ -485,6 +500,8 @@ static void etr_reset(void)
if (etr_setr(&etr_eacr) == 0) {
etr_tolec = get_clock();
set_bit(CLOCK_SYNC_HAS_ETR, &clock_sync_flags);
+ if (etr_port0_online && etr_port1_online)
+ set_bit(CLOCK_SYNC_ETR, &clock_sync_flags);
} else if (etr_port0_online || etr_port1_online) {
pr_warning("The real or virtual hardware system does "
"not provide an ETR interface\n");
@@ -533,8 +550,7 @@ void etr_switch_to_local(void)
{
if (!etr_eacr.sl)
return;
- if (test_bit(CLOCK_SYNC_ETR, &clock_sync_flags))
- disable_sync_clock(NULL);
+ disable_sync_clock(NULL);
set_bit(ETR_EVENT_SWITCH_LOCAL, &etr_events);
queue_work(time_sync_wq, &etr_work);
}
@@ -549,8 +565,7 @@ void etr_sync_check(void)
{
if (!etr_eacr.es)
return;
- if (test_bit(CLOCK_SYNC_ETR, &clock_sync_flags))
- disable_sync_clock(NULL);
+ disable_sync_clock(NULL);
set_bit(ETR_EVENT_SYNC_CHECK, &etr_events);
queue_work(time_sync_wq, &etr_work);
}
@@ -914,7 +929,7 @@ static struct etr_eacr etr_handle_update
* Do not try to get the alternate port aib if the clock
* is not in sync yet.
*/
- if (!test_bit(CLOCK_SYNC_STP, &clock_sync_flags) && !eacr.es)
+ if (!check_sync_clock())
return eacr;
/*
@@ -997,7 +1012,6 @@ static void etr_work_fn(struct work_stru
on_each_cpu(disable_sync_clock, NULL, 1);
del_timer_sync(&etr_timer);
etr_update_eacr(eacr);
- clear_bit(CLOCK_SYNC_ETR, &clock_sync_flags);
goto out_unlock;
}
@@ -1071,18 +1085,13 @@ static void etr_work_fn(struct work_stru
/* Both ports not usable. */
eacr.es = eacr.sl = 0;
sync_port = -1;
- clear_bit(CLOCK_SYNC_ETR, &clock_sync_flags);
}
- if (!test_bit(CLOCK_SYNC_ETR, &clock_sync_flags))
- eacr.es = 0;
-
/*
* If the clock is in sync just update the eacr and return.
* If there is no valid sync port wait for a port update.
*/
- if (test_bit(CLOCK_SYNC_STP, &clock_sync_flags) ||
- eacr.es || sync_port < 0) {
+ if (check_sync_clock() || sync_port < 0) {
etr_update_eacr(eacr);
etr_set_tolec_timeout(now);
goto out_unlock;
@@ -1103,13 +1112,11 @@ static void etr_work_fn(struct work_stru
* and set up a timer to try again after 0.5 seconds
*/
etr_update_eacr(eacr);
- set_bit(CLOCK_SYNC_ETR, &clock_sync_flags);
if (now < etr_tolec + (1600000 << 12) ||
etr_sync_clock_stop(&aib, sync_port) != 0) {
/* Sync failed. Try again in 1/2 second. */
eacr.es = 0;
etr_update_eacr(eacr);
- clear_bit(CLOCK_SYNC_ETR, &clock_sync_flags);
etr_set_sync_timeout();
} else
etr_set_tolec_timeout(now);
@@ -1191,19 +1198,30 @@ static ssize_t etr_online_store(struct s
return -EINVAL;
if (!test_bit(CLOCK_SYNC_HAS_ETR, &clock_sync_flags))
return -EOPNOTSUPP;
+ mutex_lock(&clock_sync_mutex);
if (dev == &etr_port0_dev) {
if (etr_port0_online == value)
- return count; /* Nothing to do. */
+ goto out; /* Nothing to do. */
etr_port0_online = value;
+ if (etr_port0_online && etr_port1_online)
+ set_bit(CLOCK_SYNC_ETR, &clock_sync_flags);
+ else
+ clear_bit(CLOCK_SYNC_ETR, &clock_sync_flags);
set_bit(ETR_EVENT_PORT0_CHANGE, &etr_events);
queue_work(time_sync_wq, &etr_work);
} else {
if (etr_port1_online == value)
- return count; /* Nothing to do. */
+ goto out; /* Nothing to do. */
etr_port1_online = value;
+ if (etr_port0_online && etr_port1_online)
+ set_bit(CLOCK_SYNC_ETR, &clock_sync_flags);
+ else
+ clear_bit(CLOCK_SYNC_ETR, &clock_sync_flags);
set_bit(ETR_EVENT_PORT1_CHANGE, &etr_events);
queue_work(time_sync_wq, &etr_work);
}
+out:
+ mutex_unlock(&clock_sync_mutex);
return count;
}
@@ -1471,8 +1489,6 @@ static void stp_timing_alert(struct stp_
*/
void stp_sync_check(void)
{
- if (!test_bit(CLOCK_SYNC_STP, &clock_sync_flags))
- return;
disable_sync_clock(NULL);
queue_work(time_sync_wq, &stp_work);
}
@@ -1485,8 +1501,6 @@ void stp_sync_check(void)
*/
void stp_island_check(void)
{
- if (!test_bit(CLOCK_SYNC_STP, &clock_sync_flags))
- return;
disable_sync_clock(NULL);
queue_work(time_sync_wq, &stp_work);
}
@@ -1513,10 +1527,6 @@ static int stp_sync_clock(void *data)
enable_sync_clock();
- set_bit(CLOCK_SYNC_STP, &clock_sync_flags);
- if (test_and_clear_bit(CLOCK_SYNC_ETR, &clock_sync_flags))
- queue_work(time_sync_wq, &etr_work);
-
rc = 0;
if (stp_info.todoff[0] || stp_info.todoff[1] ||
stp_info.todoff[2] || stp_info.todoff[3] ||
@@ -1535,9 +1545,6 @@ static int stp_sync_clock(void *data)
if (rc) {
disable_sync_clock(NULL);
stp_sync->in_sync = -EAGAIN;
- clear_bit(CLOCK_SYNC_STP, &clock_sync_flags);
- if (etr_port0_online || etr_port1_online)
- queue_work(time_sync_wq, &etr_work);
} else
stp_sync->in_sync = 1;
xchg(&first, 0);
@@ -1569,6 +1576,10 @@ static void stp_work_fn(struct work_stru
if (rc || stp_info.c == 0)
goto out_unlock;
+ /* Skip synchronization if the clock is already in sync. */
+ if (check_sync_clock())
+ goto out_unlock;
+
memset(&stp_sync, 0, sizeof(stp_sync));
get_online_cpus();
atomic_set(&stp_sync.cpus, num_online_cpus() - 1);
@@ -1684,8 +1695,14 @@ static ssize_t stp_online_store(struct s
return -EINVAL;
if (!test_bit(CLOCK_SYNC_HAS_STP, &clock_sync_flags))
return -EOPNOTSUPP;
+ mutex_lock(&clock_sync_mutex);
stp_online = value;
+ if (stp_online)
+ set_bit(CLOCK_SYNC_STP, &clock_sync_flags);
+ else
+ clear_bit(CLOCK_SYNC_STP, &clock_sync_flags);
queue_work(time_sync_wq, &stp_work);
+ mutex_unlock(&clock_sync_mutex);
return count;
}
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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