tracing: Use the perf recursion protection from trace event

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>

1 files changed, 8 insertions, 6 deletions

diff --git a/kernel/trace/trace_event_profile.c b/kernel/trace/trace_event_profile.c
index e0d351b01f5a..d9c60f80aa0d 100644
--- a/kernel/trace/trace_event_profile.c
+++ b/kernel/trace/trace_event_profile.c
@@ -9,31 +9,33 @@
 #include "trace.h"
 
 
-struct perf_trace_buf *perf_trace_buf;
+char *perf_trace_buf;
 EXPORT_SYMBOL_GPL(perf_trace_buf);
 
-struct perf_trace_buf *perf_trace_buf_nmi;
+char *perf_trace_buf_nmi;
 EXPORT_SYMBOL_GPL(perf_trace_buf_nmi);
 
+typedef typeof(char [FTRACE_MAX_PROFILE_SIZE]) perf_trace_t ;
+
 /* Count the events in use (per event id, not per instance) */
 static int      total_profile_count;
 
 static int ftrace_profile_enable_event(struct ftrace_event_call *event)
 {
-        struct perf_trace_buf *buf;
+        char *buf;
         int ret = -ENOMEM;
 
         if (atomic_inc_return(&event->profile_count))
                 return 0;
 
         if (!total_profile_count) {
-                buf = alloc_percpu(struct perf_trace_buf);
+                buf = (char *)alloc_percpu(perf_trace_t);
                 if (!buf)
                         goto fail_buf;
 
                 rcu_assign_pointer(perf_trace_buf, buf);
 
-                buf = alloc_percpu(struct perf_trace_buf);
+                buf = (char *)alloc_percpu(perf_trace_t);
                 if (!buf)
                         goto fail_buf_nmi;
 
@@ -79,7 +81,7 @@ int ftrace_profile_enable(int event_id)
 
 static void ftrace_profile_disable_event(struct ftrace_event_call *event)
 {
-        struct perf_trace_buf *buf, *nmi_buf;
+        char *buf, *nmi_buf;
 
         if (!atomic_add_negative(-1, &event->profile_count))
                 return;