[S390] clock sync mode flags

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@de.ibm.com>

1 files changed, 44 insertions, 27 deletions

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index fc468cae4460..f72d41068dc2 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -331,6 +331,7 @@ static unsigned long long adjust_time(unsigned long long old,
 }
 
 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(struct etr_aib *aib,
          * 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_struct *work)
                 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_struct *work)
                 /* 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_struct *work)
          * 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 sys_device *dev,
                 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_irq_parm *intparm)
  */
 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_struct *work)
         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 sysdev_class *class,
                 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;
 }