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When we commit a trace to perf, we first check if we are recursing in the same buffer so that we don't mess-up the buffer with a recursing trace. But later on, we do the same check from perf to avoid commit recursion. The recursion check is desired early before we touch the buffer but we want to do this check only once. Then export the recursion protection from perf and use it from the trace events before submitting a trace. v2: Put appropriate Reported-by tag Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Masami Hiramatsu <mhiramat@redhat.com> Cc: Jason Baron <jbaron@redhat.com> LKML-Reference: <1258864015-10579-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
122 lines
2.4 KiB
C
122 lines
2.4 KiB
C
/*
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* trace event based perf counter profiling
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*
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* Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
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*
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*/
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#include <linux/module.h>
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#include "trace.h"
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char *perf_trace_buf;
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EXPORT_SYMBOL_GPL(perf_trace_buf);
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char *perf_trace_buf_nmi;
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EXPORT_SYMBOL_GPL(perf_trace_buf_nmi);
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typedef typeof(char [FTRACE_MAX_PROFILE_SIZE]) 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_profile_count;
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static int ftrace_profile_enable_event(struct ftrace_event_call *event)
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{
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char *buf;
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int ret = -ENOMEM;
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if (atomic_inc_return(&event->profile_count))
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return 0;
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if (!total_profile_count) {
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buf = (char *)alloc_percpu(perf_trace_t);
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if (!buf)
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goto fail_buf;
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rcu_assign_pointer(perf_trace_buf, buf);
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buf = (char *)alloc_percpu(perf_trace_t);
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if (!buf)
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goto fail_buf_nmi;
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rcu_assign_pointer(perf_trace_buf_nmi, buf);
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}
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ret = event->profile_enable(event);
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if (!ret) {
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total_profile_count++;
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return 0;
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}
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fail_buf_nmi:
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if (!total_profile_count) {
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free_percpu(perf_trace_buf_nmi);
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free_percpu(perf_trace_buf);
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perf_trace_buf_nmi = NULL;
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perf_trace_buf = NULL;
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}
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fail_buf:
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atomic_dec(&event->profile_count);
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return ret;
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}
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int ftrace_profile_enable(int event_id)
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{
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struct ftrace_event_call *event;
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int ret = -EINVAL;
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mutex_lock(&event_mutex);
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list_for_each_entry(event, &ftrace_events, list) {
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if (event->id == event_id && event->profile_enable &&
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try_module_get(event->mod)) {
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ret = ftrace_profile_enable_event(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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static void ftrace_profile_disable_event(struct ftrace_event_call *event)
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{
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char *buf, *nmi_buf;
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if (!atomic_add_negative(-1, &event->profile_count))
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return;
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event->profile_disable(event);
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if (!--total_profile_count) {
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buf = perf_trace_buf;
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rcu_assign_pointer(perf_trace_buf, NULL);
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nmi_buf = perf_trace_buf_nmi;
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rcu_assign_pointer(perf_trace_buf_nmi, NULL);
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/*
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* Ensure every events in profiling have finished before
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* releasing the buffers
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*/
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synchronize_sched();
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free_percpu(buf);
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free_percpu(nmi_buf);
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}
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}
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void ftrace_profile_disable(int event_id)
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{
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struct ftrace_event_call *event;
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mutex_lock(&event_mutex);
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list_for_each_entry(event, &ftrace_events, list) {
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if (event->id == event_id) {
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ftrace_profile_disable_event(event);
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module_put(event->mod);
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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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}
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