1 files changed, 45 insertions, 90 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9c143739b8d7..a7a055f167c7 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -479,9 +479,7 @@ struct ring_buffer {
 
         struct ring_buffer_per_cpu      **buffers;
 
-#ifdef CONFIG_HOTPLUG_CPU
-        struct notifier_block           cpu_notify;
-#endif
+        struct hlist_node               node;
         u64                             (*clock)(void);
 
         struct rb_irq_work              irq_work;
@@ -1274,11 +1272,6 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
         kfree(cpu_buffer);
 }
 
-#ifdef CONFIG_HOTPLUG_CPU
-static int rb_cpu_notify(struct notifier_block *self,
-                         unsigned long action, void *hcpu);
-#endif
-
 /**
  * __ring_buffer_alloc - allocate a new ring_buffer
  * @size: the size in bytes per cpu that is needed.
@@ -1296,6 +1289,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
         long nr_pages;
         int bsize;
         int cpu;
+        int ret;
 
         /* keep it in its own cache line */
         buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
@@ -1318,17 +1312,6 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
         if (nr_pages < 2)
                 nr_pages = 2;
 
-        /*
-         * In case of non-hotplug cpu, if the ring-buffer is allocated
-         * in early initcall, it will not be notified of secondary cpus.
-         * In that off case, we need to allocate for all possible cpus.
-         */
-#ifdef CONFIG_HOTPLUG_CPU
-        cpu_notifier_register_begin();
-        cpumask_copy(buffer->cpumask, cpu_online_mask);
-#else
-        cpumask_copy(buffer->cpumask, cpu_possible_mask);
-#endif
         buffer->cpus = nr_cpu_ids;
 
         bsize = sizeof(void *) * nr_cpu_ids;
@@ -1337,19 +1320,15 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
         if (!buffer->buffers)
                 goto fail_free_cpumask;
 
-        for_each_buffer_cpu(buffer, cpu) {
-                buffer->buffers[cpu] =
-                        rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
-                if (!buffer->buffers[cpu])
-                        goto fail_free_buffers;
-        }
+        cpu = raw_smp_processor_id();
+        cpumask_set_cpu(cpu, buffer->cpumask);
+        buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
+        if (!buffer->buffers[cpu])
+                goto fail_free_buffers;
 
-#ifdef CONFIG_HOTPLUG_CPU
-        buffer->cpu_notify.notifier_call = rb_cpu_notify;
-        buffer->cpu_notify.priority = 0;
-        __register_cpu_notifier(&buffer->cpu_notify);
-        cpu_notifier_register_done();
-#endif
+        ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
+        if (ret < 0)
+                goto fail_free_buffers;
 
         mutex_init(&buffer->mutex);
 
@@ -1364,9 +1343,6 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 
  fail_free_cpumask:
         free_cpumask_var(buffer->cpumask);
-#ifdef CONFIG_HOTPLUG_CPU
-        cpu_notifier_register_done();
-#endif
 
  fail_free_buffer:
         kfree(buffer);
@@ -1383,18 +1359,11 @@ ring_buffer_free(struct ring_buffer *buffer)
 {
         int cpu;
 
-#ifdef CONFIG_HOTPLUG_CPU
-        cpu_notifier_register_begin();
-        __unregister_cpu_notifier(&buffer->cpu_notify);
-#endif
+        cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
 
         for_each_buffer_cpu(buffer, cpu)
                 rb_free_cpu_buffer(buffer->buffers[cpu]);
 
-#ifdef CONFIG_HOTPLUG_CPU
-        cpu_notifier_register_done();
-#endif
-
         kfree(buffer->buffers);
         free_cpumask_var(buffer->cpumask);
 
@@ -4633,62 +4602,48 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
 }
 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
 
-#ifdef CONFIG_HOTPLUG_CPU
-static int rb_cpu_notify(struct notifier_block *self,
-                         unsigned long action, void *hcpu)
+/*
+ * We only allocate new buffers, never free them if the CPU goes down.
+ * If we were to free the buffer, then the user would lose any trace that was in
+ * the buffer.
+ */
+int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
 {
-        struct ring_buffer *buffer =
-                container_of(self, struct ring_buffer, cpu_notify);
-        long cpu = (long)hcpu;
+        struct ring_buffer *buffer;
         long nr_pages_same;
         int cpu_i;
         unsigned long nr_pages;
 
-        switch (action) {
-        case CPU_UP_PREPARE:
-        case CPU_UP_PREPARE_FROZEN:
-                if (cpumask_test_cpu(cpu, buffer->cpumask))
-                        return NOTIFY_OK;
-
-                nr_pages = 0;
-                nr_pages_same = 1;
-                /* check if all cpu sizes are same */
-                for_each_buffer_cpu(buffer, cpu_i) {
-                        /* fill in the size from first enabled cpu */
-                        if (nr_pages == 0)
-                                nr_pages = buffer->buffers[cpu_i]->nr_pages;
-                        if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
-                                nr_pages_same = 0;
-                                break;
-                        }
-                }
-                /* allocate minimum pages, user can later expand it */
-                if (!nr_pages_same)
-                        nr_pages = 2;
-                buffer->buffers[cpu] =
-                        rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
-                if (!buffer->buffers[cpu]) {
-                        WARN(1, "failed to allocate ring buffer on CPU %ld\n",
-                             cpu);
-                        return NOTIFY_OK;
+        buffer = container_of(node, struct ring_buffer, node);
+        if (cpumask_test_cpu(cpu, buffer->cpumask))
+                return 0;
+
+        nr_pages = 0;
+        nr_pages_same = 1;
+        /* check if all cpu sizes are same */
+        for_each_buffer_cpu(buffer, cpu_i) {
+                /* fill in the size from first enabled cpu */
+                if (nr_pages == 0)
+                        nr_pages = buffer->buffers[cpu_i]->nr_pages;
+                if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
+                        nr_pages_same = 0;
+                        break;
                 }
-                smp_wmb();
-                cpumask_set_cpu(cpu, buffer->cpumask);
-                break;
-        case CPU_DOWN_PREPARE:
-        case CPU_DOWN_PREPARE_FROZEN:
-                /*
-                 * Do nothing.
-                 *  If we were to free the buffer, then the user would
-                 *  lose any trace that was in the buffer.
-                 */
-                break;
-        default:
-                break;
         }
-        return NOTIFY_OK;
+        /* allocate minimum pages, user can later expand it */
+        if (!nr_pages_same)
+                nr_pages = 2;
+        buffer->buffers[cpu] =
+                rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
+        if (!buffer->buffers[cpu]) {
+                WARN(1, "failed to allocate ring buffer on CPU %u\n",
+                     cpu);
+                return -ENOMEM;
+        }
+        smp_wmb();
+        cpumask_set_cpu(cpu, buffer->cpumask);
+        return 0;
 }
-#endif
 
 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
 /*