[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>

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index fc468ca..f72d410 100644 (file)
--- 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;
 }