tracing/rb: Convert to hotplug state machine
Install the callbacks via the state machine. The notifier in struct ring_buffer is replaced by the multi instance interface. Upon __ring_buffer_alloc() invocation, cpuhp_state_add_instance() will invoke the trace_rb_cpu_prepare() on each CPU. This callback may now fail. This means __ring_buffer_alloc() will fail and cleanup (like previously) and during a CPU up event this failure will not allow the CPU to come up. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: rt@linutronix.de Link: http://lkml.kernel.org/r/20161126231350.10321-7-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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@ -62,6 +62,7 @@ enum cpuhp_state {
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CPUHP_TOPOLOGY_PREPARE,
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CPUHP_NET_IUCV_PREPARE,
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CPUHP_ARM_BL_PREPARE,
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CPUHP_TRACE_RB_PREPARE,
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CPUHP_TIMERS_DEAD,
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CPUHP_NOTF_ERR_INJ_PREPARE,
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CPUHP_MIPS_SOC_PREPARE,
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@ -198,4 +198,10 @@ enum ring_buffer_flags {
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RB_FL_OVERWRITE = 1 << 0,
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};
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#ifdef CONFIG_RING_BUFFER
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int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node);
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#else
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#define trace_rb_cpu_prepare NULL
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#endif
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#endif /* _LINUX_RING_BUFFER_H */
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@ -479,9 +479,7 @@ struct ring_buffer {
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struct ring_buffer_per_cpu **buffers;
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#ifdef CONFIG_HOTPLUG_CPU
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struct notifier_block cpu_notify;
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#endif
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struct hlist_node node;
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u64 (*clock)(void);
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struct rb_irq_work irq_work;
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@ -1274,11 +1272,6 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
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kfree(cpu_buffer);
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}
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#ifdef CONFIG_HOTPLUG_CPU
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static int rb_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu);
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#endif
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/**
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* __ring_buffer_alloc - allocate a new ring_buffer
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* @size: the size in bytes per cpu that is needed.
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@ -1296,6 +1289,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
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long nr_pages;
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int bsize;
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int cpu;
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int ret;
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/* keep it in its own cache line */
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buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
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@ -1318,17 +1312,6 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
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if (nr_pages < 2)
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nr_pages = 2;
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/*
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* In case of non-hotplug cpu, if the ring-buffer is allocated
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* in early initcall, it will not be notified of secondary cpus.
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* In that off case, we need to allocate for all possible cpus.
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*/
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#ifdef CONFIG_HOTPLUG_CPU
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cpu_notifier_register_begin();
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cpumask_copy(buffer->cpumask, cpu_online_mask);
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#else
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cpumask_copy(buffer->cpumask, cpu_possible_mask);
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#endif
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buffer->cpus = nr_cpu_ids;
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bsize = sizeof(void *) * nr_cpu_ids;
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@ -1337,19 +1320,15 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
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if (!buffer->buffers)
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goto fail_free_cpumask;
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for_each_buffer_cpu(buffer, cpu) {
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buffer->buffers[cpu] =
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rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
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if (!buffer->buffers[cpu])
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goto fail_free_buffers;
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}
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cpu = raw_smp_processor_id();
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cpumask_set_cpu(cpu, buffer->cpumask);
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buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
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if (!buffer->buffers[cpu])
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goto fail_free_buffers;
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#ifdef CONFIG_HOTPLUG_CPU
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buffer->cpu_notify.notifier_call = rb_cpu_notify;
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buffer->cpu_notify.priority = 0;
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__register_cpu_notifier(&buffer->cpu_notify);
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cpu_notifier_register_done();
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#endif
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ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
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if (ret < 0)
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goto fail_free_buffers;
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mutex_init(&buffer->mutex);
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@ -1364,9 +1343,6 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
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fail_free_cpumask:
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free_cpumask_var(buffer->cpumask);
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#ifdef CONFIG_HOTPLUG_CPU
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cpu_notifier_register_done();
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#endif
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fail_free_buffer:
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kfree(buffer);
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@ -1383,18 +1359,11 @@ ring_buffer_free(struct ring_buffer *buffer)
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{
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int cpu;
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#ifdef CONFIG_HOTPLUG_CPU
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cpu_notifier_register_begin();
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__unregister_cpu_notifier(&buffer->cpu_notify);
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#endif
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cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
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for_each_buffer_cpu(buffer, cpu)
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rb_free_cpu_buffer(buffer->buffers[cpu]);
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#ifdef CONFIG_HOTPLUG_CPU
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cpu_notifier_register_done();
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#endif
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kfree(buffer->buffers);
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free_cpumask_var(buffer->cpumask);
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@ -4633,62 +4602,48 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
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}
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EXPORT_SYMBOL_GPL(ring_buffer_read_page);
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#ifdef CONFIG_HOTPLUG_CPU
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static int rb_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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/*
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* We only allocate new buffers, never free them if the CPU goes down.
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* If we were to free the buffer, then the user would lose any trace that was in
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* the buffer.
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*/
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int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
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{
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struct ring_buffer *buffer =
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container_of(self, struct ring_buffer, cpu_notify);
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long cpu = (long)hcpu;
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struct ring_buffer *buffer;
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long nr_pages_same;
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int cpu_i;
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unsigned long nr_pages;
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switch (action) {
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case CPU_UP_PREPARE:
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case CPU_UP_PREPARE_FROZEN:
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if (cpumask_test_cpu(cpu, buffer->cpumask))
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return NOTIFY_OK;
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buffer = container_of(node, struct ring_buffer, node);
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if (cpumask_test_cpu(cpu, buffer->cpumask))
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return 0;
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nr_pages = 0;
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nr_pages_same = 1;
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/* check if all cpu sizes are same */
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for_each_buffer_cpu(buffer, cpu_i) {
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/* fill in the size from first enabled cpu */
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if (nr_pages == 0)
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nr_pages = buffer->buffers[cpu_i]->nr_pages;
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if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
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nr_pages_same = 0;
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break;
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}
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nr_pages = 0;
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nr_pages_same = 1;
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/* check if all cpu sizes are same */
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for_each_buffer_cpu(buffer, cpu_i) {
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/* fill in the size from first enabled cpu */
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if (nr_pages == 0)
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nr_pages = buffer->buffers[cpu_i]->nr_pages;
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if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
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nr_pages_same = 0;
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break;
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}
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/* allocate minimum pages, user can later expand it */
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if (!nr_pages_same)
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nr_pages = 2;
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buffer->buffers[cpu] =
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rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
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if (!buffer->buffers[cpu]) {
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WARN(1, "failed to allocate ring buffer on CPU %ld\n",
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cpu);
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return NOTIFY_OK;
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}
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smp_wmb();
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cpumask_set_cpu(cpu, buffer->cpumask);
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break;
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case CPU_DOWN_PREPARE:
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case CPU_DOWN_PREPARE_FROZEN:
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/*
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* Do nothing.
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* If we were to free the buffer, then the user would
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* lose any trace that was in the buffer.
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*/
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break;
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default:
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break;
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}
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return NOTIFY_OK;
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/* allocate minimum pages, user can later expand it */
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if (!nr_pages_same)
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nr_pages = 2;
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buffer->buffers[cpu] =
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rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
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if (!buffer->buffers[cpu]) {
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WARN(1, "failed to allocate ring buffer on CPU %u\n",
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cpu);
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return -ENOMEM;
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}
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smp_wmb();
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cpumask_set_cpu(cpu, buffer->cpumask);
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return 0;
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}
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#endif
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#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
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/*
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@ -7659,10 +7659,21 @@ __init static int tracer_alloc_buffers(void)
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raw_spin_lock_init(&global_trace.start_lock);
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/*
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* The prepare callbacks allocates some memory for the ring buffer. We
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* don't free the buffer if the if the CPU goes down. If we were to free
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* the buffer, then the user would lose any trace that was in the
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* buffer. The memory will be removed once the "instance" is removed.
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*/
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ret = cpuhp_setup_state_multi(CPUHP_TRACE_RB_PREPARE,
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"trace/RB:preapre", trace_rb_cpu_prepare,
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NULL);
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if (ret < 0)
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goto out_free_cpumask;
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/* Used for event triggers */
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temp_buffer = ring_buffer_alloc(PAGE_SIZE, RB_FL_OVERWRITE);
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if (!temp_buffer)
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goto out_free_cpumask;
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goto out_rm_hp_state;
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if (trace_create_savedcmd() < 0)
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goto out_free_temp_buffer;
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free_saved_cmdlines_buffer(savedcmd);
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out_free_temp_buffer:
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ring_buffer_free(temp_buffer);
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out_rm_hp_state:
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cpuhp_remove_multi_state(CPUHP_TRACE_RB_PREPARE);
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out_free_cpumask:
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free_cpumask_var(global_trace.tracing_cpumask);
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out_free_buffer_mask:
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