[Xen-devel] [PATCH v4 2/6] xen: add helper for calling notifier_call_chain() to common/cpu.c

[Juergen Gross <jgross@xxxxxxxx>]

Add a helper cpu_notifier_call_chain() to call notifier_call_chain()
for a cpu with a specified action, returning an errno value.

This avoids coding the same pattern multiple times.

While at it avoid side effects from using BUG_ON() by not using
cpu_online(cpu) as a parameter.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
V2:
- add nofail parameter to cpu_notifier_call_chain()
- avoid side effects from using BUG_ON() macro (Andrew Cooper)
---
 xen/common/cpu.c | 56 ++++++++++++++++++++++++++------------------------------
 1 file changed, 26 insertions(+), 30 deletions(-)

diff --git a/xen/common/cpu.c b/xen/common/cpu.c
index 836c62f97f..8bf69600a6 100644
--- a/xen/common/cpu.c
+++ b/xen/common/cpu.c
@@ -71,11 +71,21 @@ void __init register_cpu_notifier(struct notifier_block *nb)
     spin_unlock(&cpu_add_remove_lock);
 }
 
+static int cpu_notifier_call_chain(unsigned int cpu, unsigned long action,
+                                   struct notifier_block **nb, bool nofail)
+{
+    void *hcpu = (void *)(long)cpu;
+    int notifier_rc = notifier_call_chain(&cpu_chain, action, hcpu, nb);
+    int ret = (notifier_rc == NOTIFY_DONE) ? 0 : 
notifier_to_errno(notifier_rc);
+
+    BUG_ON(ret && nofail);
+
+    return ret;
+}
+
 static void _take_cpu_down(void *unused)
 {
-    void *hcpu = (void *)(long)smp_processor_id();
-    int notifier_rc = notifier_call_chain(&cpu_chain, CPU_DYING, hcpu, NULL);
-    BUG_ON(notifier_rc != NOTIFY_DONE);
+    cpu_notifier_call_chain(smp_processor_id(), CPU_DYING, NULL, true);
     __cpu_disable();
 }
 
@@ -87,8 +97,7 @@ static int take_cpu_down(void *arg)
 
 int cpu_down(unsigned int cpu)
 {
-    int err, notifier_rc;
-    void *hcpu = (void *)(long)cpu;
+    int err;
     struct notifier_block *nb = NULL;
 
     if ( !cpu_hotplug_begin() )
@@ -100,12 +109,9 @@ int cpu_down(unsigned int cpu)
         return -EINVAL;
     }
 
-    notifier_rc = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, hcpu, &nb);
-    if ( notifier_rc != NOTIFY_DONE )
-    {
-        err = notifier_to_errno(notifier_rc);
+    err = cpu_notifier_call_chain(cpu, CPU_DOWN_PREPARE, &nb, false);
+    if ( err )
         goto fail;
-    }
 
     if ( unlikely(system_state < SYS_STATE_active) )
         on_selected_cpus(cpumask_of(cpu), _take_cpu_down, NULL, true);
@@ -113,26 +119,24 @@ int cpu_down(unsigned int cpu)
         goto fail;
 
     __cpu_die(cpu);
-    BUG_ON(cpu_online(cpu));
+    err = cpu_online(cpu);
+    BUG_ON(err);
 
-    notifier_rc = notifier_call_chain(&cpu_chain, CPU_DEAD, hcpu, NULL);
-    BUG_ON(notifier_rc != NOTIFY_DONE);
+    cpu_notifier_call_chain(cpu, CPU_DEAD, NULL, true);
 
     send_global_virq(VIRQ_PCPU_STATE);
     cpu_hotplug_done();
     return 0;
 
  fail:
-    notifier_rc = notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, hcpu, &nb);
-    BUG_ON(notifier_rc != NOTIFY_DONE);
+    cpu_notifier_call_chain(cpu, CPU_DOWN_FAILED, &nb, true);
     cpu_hotplug_done();
     return err;
 }
 
 int cpu_up(unsigned int cpu)
 {
-    int notifier_rc, err = 0;
-    void *hcpu = (void *)(long)cpu;
+    int err;
     struct notifier_block *nb = NULL;
 
     if ( !cpu_hotplug_begin() )
@@ -144,19 +148,15 @@ int cpu_up(unsigned int cpu)
         return -EINVAL;
     }
 
-    notifier_rc = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu, &nb);
-    if ( notifier_rc != NOTIFY_DONE )
-    {
-        err = notifier_to_errno(notifier_rc);
+    err = cpu_notifier_call_chain(cpu, CPU_UP_PREPARE, &nb, false);
+    if ( err )
         goto fail;
-    }
 
     err = __cpu_up(cpu);
     if ( err < 0 )
         goto fail;
 
-    notifier_rc = notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu, NULL);
-    BUG_ON(notifier_rc != NOTIFY_DONE);
+    cpu_notifier_call_chain(cpu, CPU_ONLINE, NULL, true);
 
     send_global_virq(VIRQ_PCPU_STATE);
 
@@ -164,18 +164,14 @@ int cpu_up(unsigned int cpu)
     return 0;
 
  fail:
-    notifier_rc = notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu, &nb);
-    BUG_ON(notifier_rc != NOTIFY_DONE);
+    cpu_notifier_call_chain(cpu, CPU_UP_CANCELED, &nb, true);
     cpu_hotplug_done();
     return err;
 }
 
 void notify_cpu_starting(unsigned int cpu)
 {
-    void *hcpu = (void *)(long)cpu;
-    int notifier_rc = notifier_call_chain(
-        &cpu_chain, CPU_STARTING, hcpu, NULL);
-    BUG_ON(notifier_rc != NOTIFY_DONE);
+    cpu_notifier_call_chain(cpu, CPU_STARTING, NULL, true);
 }
 
 static cpumask_t frozen_cpus;
-- 
2.16.4


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