diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c
index 2b7101ea25..69c30aecd8 100644
--- a/xen/arch/arm/cpuerrata.c
+++ b/xen/arch/arm/cpuerrata.c
@@ -730,6 +730,7 @@ static int cpu_errata_callback(struct notifier_block *nfb,
         rc = enable_nonboot_cpu_caps(arm_errata);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 3eaf670fd7..dc5408a456 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -463,6 +463,7 @@ static int cpu_gic_callback(struct notifier_block *nfb,
         release_irq(gic_hw_ops->info->maintenance_irq, NULL);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index c60502444c..61ca6f5b87 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -127,6 +127,10 @@ static int cpu_callback(struct notifier_block *nfb, unsigned long action,
             printk(XENLOG_ERR "Unable to allocate local IRQ for CPU%u\n",
                    cpu);
         break;
+
+    default:
+        /* Notifier pattern. */
+        break;
     }
 
     return notifier_from_errno(rc);
diff --git a/xen/arch/arm/mmu/p2m.c b/xen/arch/arm/mmu/p2m.c
index 1725cca649..bf7c66155d 100644
--- a/xen/arch/arm/mmu/p2m.c
+++ b/xen/arch/arm/mmu/p2m.c
@@ -1839,6 +1839,7 @@ static int cpu_virt_paging_callback(struct notifier_block *nfb,
         setup_virt_paging_one(NULL);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/arch/arm/percpu.c b/xen/arch/arm/percpu.c
index 87fe960330..81f91f05bb 100644
--- a/xen/arch/arm/percpu.c
+++ b/xen/arch/arm/percpu.c
@@ -66,6 +66,7 @@ static int cpu_percpu_callback(
         free_percpu_area(cpu);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index 04e363088d..3d481e59f9 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -591,6 +591,7 @@ static int cpu_smpboot_callback(struct notifier_block *nfb,
         remove_cpu_sibling_map(cpu);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/arch/arm/time.c b/xen/arch/arm/time.c
index e74d30d258..27cbfae874 100644
--- a/xen/arch/arm/time.c
+++ b/xen/arch/arm/time.c
@@ -382,6 +382,7 @@ static int cpu_time_callback(struct notifier_block *nfb,
         deinit_timer_interrupt();
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
index 70b5aeb822..a33ff64ff2 100644
--- a/xen/arch/arm/vgic-v3-its.c
+++ b/xen/arch/arm/vgic-v3-its.c
@@ -1194,6 +1194,7 @@ static void sanitize_its_base_reg(uint64_t *reg)
         r |= GIC_BASER_InnerShareable << GITS_BASER_SHAREABILITY_SHIFT;
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
@@ -1206,6 +1207,7 @@ static void sanitize_its_base_reg(uint64_t *reg)
         r |= GIC_BASER_CACHE_RaWb << GITS_BASER_INNER_CACHEABILITY_SHIFT;
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
index 32c1b2756b..222b174bbb 100644
--- a/xen/arch/x86/cpu/mcheck/mce.c
+++ b/xen/arch/x86/cpu/mcheck/mce.c
@@ -722,6 +722,10 @@ static int cf_check cpu_callback(
         if ( park_offline_cpus )
             cpu_bank_free(cpu);
         break;
+
+    default:
+        /* Notifier pattern. */
+        break;
     }
 
     return notifier_from_errno(rc);
diff --git a/xen/arch/x86/genapic/x2apic.c b/xen/arch/x86/genapic/x2apic.c
index 371dd100c7..d271102f9f 100644
--- a/xen/arch/x86/genapic/x2apic.c
+++ b/xen/arch/x86/genapic/x2apic.c
@@ -238,6 +238,9 @@ static int cf_check update_clusterinfo(
         }
         FREE_CPUMASK_VAR(per_cpu(scratch_mask, cpu));
         break;
+    default:
+        /* Notifier pattern. */
+        break;
     }
 
     return notifier_from_errno(err);
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 8334ab1711..00c360cf24 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -123,6 +123,7 @@ static int cf_check cpu_callback(
         alternative_vcall(hvm_funcs.cpu_dead, cpu);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/arch/x86/nmi.c b/xen/arch/x86/nmi.c
index 9793fa2316..105efa5a71 100644
--- a/xen/arch/x86/nmi.c
+++ b/xen/arch/x86/nmi.c
@@ -434,6 +434,7 @@ static int cf_check cpu_nmi_callback(
         kill_timer(&per_cpu(nmi_timer, cpu));
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/arch/x86/percpu.c b/xen/arch/x86/percpu.c
index 3205eacea6..627b56b9f3 100644
--- a/xen/arch/x86/percpu.c
+++ b/xen/arch/x86/percpu.c
@@ -84,6 +84,9 @@ static int cf_check cpu_percpu_callback(
         if ( park_offline_cpus )
             free_percpu_area(cpu);
         break;
+    default:
+        /* Notifier pattern. */
+        break;
     }
 
     return notifier_from_errno(rc);
diff --git a/xen/arch/x86/psr.c b/xen/arch/x86/psr.c
index 0b9631ac44..e76b129e6c 100644
--- a/xen/arch/x86/psr.c
+++ b/xen/arch/x86/psr.c
@@ -1661,6 +1661,9 @@ static int cf_check cpu_callback(
     case CPU_DEAD:
         psr_cpu_fini(cpu);
         break;
+    default:
+        /* Notifier pattern. */
+        break;
     }
 
     return notifier_from_errno(rc);
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 8aa621533f..5b9b196d58 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -1134,6 +1134,9 @@ static int cf_check cpu_smpboot_callback(
     case CPU_REMOVE:
         cpu_smpboot_free(cpu, true);
         break;
+    default:
+        /* Notifier pattern. */
+        break;
     }
 
     return notifier_from_errno(rc);
diff --git a/xen/common/rcupdate.c b/xen/common/rcupdate.c
index 212a99acd8..0fe4097544 100644
--- a/xen/common/rcupdate.c
+++ b/xen/common/rcupdate.c
@@ -657,6 +657,7 @@ static int cf_check cpu_callback(
         rcu_offline_cpu(&this_cpu(rcu_data), &rcu_ctrlblk, rdp);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index d84b65f197..dffa1ef476 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -2907,6 +2907,7 @@ static int cf_check cpu_schedule_callback(
         cpu_schedule_down(cpu);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index ad8f608462..c7117f4243 100644
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -1073,6 +1073,7 @@ static int cf_check cpu_callback(
         cpupool_cpu_remove_forced(cpu);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/common/spinlock.c b/xen/common/spinlock.c
index 28c6e9d3ac..bf082478db 100644
--- a/xen/common/spinlock.c
+++ b/xen/common/spinlock.c
@@ -55,6 +55,7 @@ static int cf_check cpu_lockdebug_callback(struct notifier_block *nfb,
         break;
 
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/common/tasklet.c b/xen/common/tasklet.c
index 4c8d87a338..879b1f0d80 100644
--- a/xen/common/tasklet.c
+++ b/xen/common/tasklet.c
@@ -232,6 +232,7 @@ static int cf_check cpu_callback(
         migrate_tasklets_from_cpu(cpu, &per_cpu(softirq_tasklet_list, cpu));
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/common/timer.c b/xen/common/timer.c
index a21798b76f..60e9a1493e 100644
--- a/xen/common/timer.c
+++ b/xen/common/timer.c
@@ -677,6 +677,7 @@ static int cf_check cpu_callback(
         break;
 
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/drivers/cpufreq/cpufreq.c b/xen/drivers/cpufreq/cpufreq.c
index 8659ad3aee..9584b55398 100644
--- a/xen/drivers/cpufreq/cpufreq.c
+++ b/xen/drivers/cpufreq/cpufreq.c
@@ -682,6 +682,7 @@ static int cf_check cpu_callback(
         (void)cpufreq_del_cpu(cpu);
         break;
     default:
+        /* Notifier pattern. */
         break;
     }
 
diff --git a/xen/drivers/passthrough/x86/hvm.c b/xen/drivers/passthrough/x86/hvm.c
index d3627e4af7..e5b6be4794 100644
--- a/xen/drivers/passthrough/x86/hvm.c
+++ b/xen/drivers/passthrough/x86/hvm.c
@@ -1122,6 +1122,9 @@ static int cf_check cpu_callback(
          */
         ASSERT(list_empty(&per_cpu(dpci_list, cpu)));
         break;
+    default:
+        /* Notifier pattern. */
+        break;
     }
 
     return NOTIFY_DONE;
diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c
index cc0062b027..f0c84eeb85 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -749,6 +749,9 @@ static int cf_check cpu_callback(
         if ( !page_list_empty(list) )
             tasklet_schedule(tasklet);
         break;
+    default:
+        /* Notifier pattern. */
+        break;
     }
 
     return NOTIFY_DONE;
