[S390] topology: increase poll frequency if change is anticipated

Increase cpu topology change poll frequency if a change is anticipated.
Otherwise a user might be a bit confused to have to wait up to a minute
in order to see a change this should be visible immediatly.
However there is no guarantee that the change will happen during the
time frame the poll frequency is increased.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 28 insertions, 8 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 109e7422bb20..8aba77df68a9 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -867,6 +867,7 @@ static ssize_t cpu_configure_store(struct sys_device *dev,
                         if (!rc) {
                                 smp_cpu_state[cpu] = CPU_STATE_STANDBY;
                                 cpu_set_polarization(cpu, POLARIZATION_UNKNOWN);
+                                topology_expect_change();
                         }
                 }
                 break;
@@ -876,6 +877,7 @@ static ssize_t cpu_configure_store(struct sys_device *dev,
                         if (!rc) {
                                 smp_cpu_state[cpu] = CPU_STATE_CONFIGURED;
                                 cpu_set_polarization(cpu, POLARIZATION_UNKNOWN);
+                                topology_expect_change();
                         }
                 }
                 break;
diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index 2abad3014928..e06fb852d386 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -31,7 +31,6 @@ struct mask_info {
 static int topology_enabled = 1;
 static void topology_work_fn(struct work_struct *work);
 static struct sysinfo_15_1_x *tl_info;
-static struct timer_list topology_timer;
 static void set_topology_timer(void);
 static DECLARE_WORK(topology_work, topology_work_fn);
 /* topology_lock protects the core linked list */
@@ -297,12 +296,30 @@ static void topology_timer_fn(unsigned long ignored)
         set_topology_timer();
 }
 
+static struct timer_list topology_timer =
+        TIMER_DEFERRED_INITIALIZER(topology_timer_fn, 0, 0);
+
+static atomic_t topology_poll = ATOMIC_INIT(0);
+
 static void set_topology_timer(void)
 {
-        topology_timer.function = topology_timer_fn;
-        topology_timer.data = 0;
-        topology_timer.expires = jiffies + 60 * HZ;
-        add_timer(&topology_timer);
+        if (atomic_add_unless(&topology_poll, -1, 0))
+                mod_timer(&topology_timer, jiffies + HZ / 10);
+        else
+                mod_timer(&topology_timer, jiffies + HZ * 60);
+}
+
+void topology_expect_change(void)
+{
+        if (!MACHINE_HAS_TOPOLOGY)
+                return;
+        /* This is racy, but it doesn't matter since it is just a heuristic.
+         * Worst case is that we poll in a higher frequency for a bit longer.
+         */
+        if (atomic_read(&topology_poll) > 60)
+                return;
+        atomic_add(60, &topology_poll);
+        set_topology_timer();
 }
 
 static int __init early_parse_topology(char *p)
@@ -379,8 +396,10 @@ static ssize_t dispatching_store(struct sysdev_class *dev,
         if (cpu_management == val)
                 goto out;
         rc = topology_set_cpu_management(val);
-        if (!rc)
-                cpu_management = val;
+        if (rc)
+                goto out;
+        cpu_management = val;
+        topology_expect_change();
 out:
         mutex_unlock(&smp_cpu_state_mutex);
         put_online_cpus();
@@ -438,7 +457,6 @@ static int __init topology_init(void)
                 topology_update_polarization_simple();
                 goto out;
         }
-        init_timer_deferrable(&topology_timer);
         set_topology_timer();
 out:
         update_cpu_core_map();