![Frederic Weisbecker](/assets/img/avatar_default.png)
We use synchronize_sched() to ensure a tracepoint won't be called while/after we release the perf buffers it references. But the tracepoint API has its own API for that: tracepoint_synchronize_unregister(). Use it instead as it's self-explanatory and eases maintainance. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Li Zefan <lizf@cn.fujitsu.com>
181 lines
3.7 KiB
C
181 lines
3.7 KiB
C
/*
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* trace event based perf event profiling/tracing
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*
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* Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
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* Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
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*/
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#include <linux/module.h>
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#include <linux/kprobes.h>
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#include "trace.h"
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static char *perf_trace_buf[4];
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/*
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* Force it to be aligned to unsigned long to avoid misaligned accesses
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* suprises
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*/
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typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
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perf_trace_t;
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/* Count the events in use (per event id, not per instance) */
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static int total_ref_count;
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static int perf_trace_event_init(struct ftrace_event_call *tp_event,
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struct perf_event *p_event)
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{
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struct hlist_head *list;
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int ret = -ENOMEM;
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int cpu;
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p_event->tp_event = tp_event;
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if (tp_event->perf_refcount++ > 0)
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return 0;
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list = alloc_percpu(struct hlist_head);
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if (!list)
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goto fail;
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for_each_possible_cpu(cpu)
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INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));
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tp_event->perf_events = list;
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if (!total_ref_count) {
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char *buf;
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int i;
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for (i = 0; i < 4; i++) {
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buf = (char *)alloc_percpu(perf_trace_t);
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if (!buf)
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goto fail;
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perf_trace_buf[i] = buf;
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}
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}
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ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER);
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if (ret)
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goto fail;
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total_ref_count++;
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return 0;
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fail:
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if (!total_ref_count) {
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int i;
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for (i = 0; i < 4; i++) {
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free_percpu(perf_trace_buf[i]);
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perf_trace_buf[i] = NULL;
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}
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}
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if (!--tp_event->perf_refcount) {
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free_percpu(tp_event->perf_events);
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tp_event->perf_events = NULL;
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}
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return ret;
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}
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int perf_trace_init(struct perf_event *p_event)
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{
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struct ftrace_event_call *tp_event;
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int event_id = p_event->attr.config;
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int ret = -EINVAL;
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mutex_lock(&event_mutex);
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list_for_each_entry(tp_event, &ftrace_events, list) {
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if (tp_event->event.type == event_id &&
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tp_event->class && tp_event->class->reg &&
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try_module_get(tp_event->mod)) {
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ret = perf_trace_event_init(tp_event, p_event);
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break;
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}
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}
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mutex_unlock(&event_mutex);
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return ret;
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}
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int perf_trace_enable(struct perf_event *p_event)
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{
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struct ftrace_event_call *tp_event = p_event->tp_event;
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struct hlist_head *list;
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list = tp_event->perf_events;
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if (WARN_ON_ONCE(!list))
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return -EINVAL;
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list = this_cpu_ptr(list);
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hlist_add_head_rcu(&p_event->hlist_entry, list);
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return 0;
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}
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void perf_trace_disable(struct perf_event *p_event)
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{
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hlist_del_rcu(&p_event->hlist_entry);
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}
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void perf_trace_destroy(struct perf_event *p_event)
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{
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struct ftrace_event_call *tp_event = p_event->tp_event;
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int i;
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mutex_lock(&event_mutex);
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if (--tp_event->perf_refcount > 0)
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goto out;
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tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER);
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/*
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* Ensure our callback won't be called anymore. The buffers
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* will be freed after that.
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*/
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tracepoint_synchronize_unregister();
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free_percpu(tp_event->perf_events);
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tp_event->perf_events = NULL;
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if (!--total_ref_count) {
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for (i = 0; i < 4; i++) {
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free_percpu(perf_trace_buf[i]);
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perf_trace_buf[i] = NULL;
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}
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}
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out:
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mutex_unlock(&event_mutex);
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}
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__kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
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struct pt_regs *regs, int *rctxp)
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{
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struct trace_entry *entry;
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unsigned long flags;
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char *raw_data;
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int pc;
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BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
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pc = preempt_count();
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*rctxp = perf_swevent_get_recursion_context();
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if (*rctxp < 0)
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return NULL;
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raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);
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/* zero the dead bytes from align to not leak stack to user */
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memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
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entry = (struct trace_entry *)raw_data;
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local_save_flags(flags);
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tracing_generic_entry_update(entry, flags, pc);
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entry->type = type;
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return raw_data;
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}
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EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
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