[Xen-devel] [PATCH 2/2] xen/events: Convert to hotplug state machine

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
Changes from Sebastian's original version:
* Renamed hotplug state from CPUHP_XEN_EV_PREPEARE to CPUHP_XEN_EVTCHN_PREPARE
* Dropped suggestion in the commit messages about moving 
evtchn_fifo_alloc_control_block
  call since I think it is in the right place right now.


 drivers/xen/events/events_fifo.c |   34 ++++++++++++----------------------
 include/linux/cpuhotplug.h       |    1 +
 2 files changed, 13 insertions(+), 22 deletions(-)

diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c
index 266c2c7..7ef27c6 100644
--- a/drivers/xen/events/events_fifo.c
+++ b/drivers/xen/events/events_fifo.c
@@ -418,30 +418,18 @@ static int evtchn_fifo_alloc_control_block(unsigned cpu)
        return ret;
 }
 
-static int evtchn_fifo_cpu_notification(struct notifier_block *self,
-                                                 unsigned long action,
-                                                 void *hcpu)
+static int xen_evtchn_cpu_prepare(unsigned int cpu)
 {
-       int cpu = (long)hcpu;
-       int ret = 0;
-
-       switch (action) {
-       case CPU_UP_PREPARE:
-               if (!per_cpu(cpu_control_block, cpu))
-                       ret = evtchn_fifo_alloc_control_block(cpu);
-               break;
-       case CPU_DEAD:
-               __evtchn_fifo_handle_events(cpu, true);
-               break;
-       default:
-               break;
-       }
-       return ret < 0 ? NOTIFY_BAD : NOTIFY_OK;
+       if (!per_cpu(cpu_control_block, cpu))
+               return evtchn_fifo_alloc_control_block(cpu);
+       return 0;
 }
 
-static struct notifier_block evtchn_fifo_cpu_notifier = {
-       .notifier_call  = evtchn_fifo_cpu_notification,
-};
+static int xen_evtchn_cpu_dead(unsigned int cpu)
+{
+       __evtchn_fifo_handle_events(cpu, true);
+       return 0;
+}
 
 int __init xen_evtchn_fifo_init(void)
 {
@@ -456,7 +444,9 @@ int __init xen_evtchn_fifo_init(void)
 
        evtchn_ops = &evtchn_ops_fifo;
 
-       register_cpu_notifier(&evtchn_fifo_cpu_notifier);
+       cpuhp_setup_state_nocalls(CPUHP_XEN_EVTCHN_PREPARE,
+                                 "CPUHP_XEN_EVTCHN_PREPARE",
+                                 xen_evtchn_cpu_prepare, xen_evtchn_cpu_dead);
 out:
        put_cpu();
        return ret;
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index d6beeb9..c60a17c 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -22,6 +22,7 @@ enum cpuhp_state {
        CPUHP_SMPCFD_PREPARE,
        CPUHP_RCUTREE_PREP,
        CPUHP_XEN_PREPARE,
+       CPUHP_XEN_EVTCHN_PREPARE,
        CPUHP_NOTIFY_PREPARE,
        CPUHP_TIMERS_DEAD,
        CPUHP_BRINGUP_CPU,
-- 
1.7.1


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