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, 12 insertions, 11 deletions

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 4945d1c99864..c222ef5238bf 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -724,16 +724,19 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
 static void ftrace_profile_##call(proto)                                \
 {                                                                       \
         struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\
+        extern int perf_swevent_get_recursion_context(int **recursion); \
+        extern void perf_swevent_put_recursion_context(int *recursion); \
         struct ftrace_event_call *event_call = &event_##call;           \
         extern void perf_tp_event(int, u64, u64, void *, int);          \
         struct ftrace_raw_##call *entry;                                \
-        struct perf_trace_buf *trace_buf;                               \
         u64 __addr = 0, __count = 1;                                    \
         unsigned long irq_flags;                                        \
         struct trace_entry *ent;                                        \
         int __entry_size;                                               \
         int __data_size;                                                \
+        char *trace_buf;                                                \
         char *raw_data;                                                 \
+        int *recursion;                                                 \
         int __cpu;                                                      \
         int pc;                                                         \
                                                                         \
@@ -749,6 +752,10 @@ static void ftrace_profile_##call(proto)				\
                 return;                                                 \
                                                                         \
         local_irq_save(irq_flags);                                      \
+                                                                        \
+        if (perf_swevent_get_recursion_context(&recursion))             \
+                goto end_recursion;                                             \
+                                                                        \
         __cpu = smp_processor_id();                                     \
                                                                         \
         if (in_nmi())                                                   \
@@ -759,13 +766,7 @@ static void ftrace_profile_##call(proto)				\
         if (!trace_buf)                                                 \
                 goto end;                                               \
                                                                         \
-        trace_buf = per_cpu_ptr(trace_buf, __cpu);                      \
-        if (trace_buf->recursion++)                                     \
-                goto end_recursion;                                     \
-                                                                        \
-        barrier();                                                      \
-                                                                        \
-        raw_data = trace_buf->buf;                                      \
+        raw_data = per_cpu_ptr(trace_buf, __cpu);                       \
                                                                         \
         *(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL;         \
         entry = (struct ftrace_raw_##call *)raw_data;                   \
@@ -780,9 +781,9 @@ static void ftrace_profile_##call(proto)				\
         perf_tp_event(event_call->id, __addr, __count, entry,           \
                              __entry_size);                             \
                                                                         \
-end_recursion:                                                          \
-        trace_buf->recursion--;                                         \
-end:                                                                    \
+end:                                                            \
+        perf_swevent_put_recursion_context(recursion);                  \
+end_recursion:                                                                  \
         local_irq_restore(irq_flags);                                   \
                                                                         \
 }