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>

3 files changed, 18 insertions, 18 deletions

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 43360c1d8f70..47bbdf9c38d0 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -137,13 +137,8 @@ struct ftrace_event_call {
 
 #define FTRACE_MAX_PROFILE_SIZE 2048
 
-struct perf_trace_buf {
-        char    buf[FTRACE_MAX_PROFILE_SIZE];
-        int     recursion;
-};
-
-extern struct perf_trace_buf    *perf_trace_buf;
-extern struct perf_trace_buf    *perf_trace_buf_nmi;
+extern char *perf_trace_buf;
+extern char *perf_trace_buf_nmi;
 
 #define MAX_FILTER_PRED         32
 #define MAX_FILTER_STR_VAL      256     /* Should handle KSYM_SYMBOL_LEN */
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 36fe89f72641..74e98b1d3391 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -874,6 +874,8 @@ extern int perf_output_begin(struct perf_output_handle *handle,
 extern void perf_output_end(struct perf_output_handle *handle);
 extern void perf_output_copy(struct perf_output_handle *handle,
                              const void *buf, unsigned int len);
+extern int perf_swevent_get_recursion_context(int **recursion);
+extern void perf_swevent_put_recursion_context(int *recursion);
 #else
 static inline void
 perf_event_task_sched_in(struct task_struct *task, int cpu)             { }
@@ -902,6 +904,8 @@ static inline void perf_event_mmap(struct vm_area_struct *vma)		{ }
 static inline void perf_event_comm(struct task_struct *tsk)             { }
 static inline void perf_event_fork(struct task_struct *tsk)             { }
 static inline void perf_event_init(void)                                { }
+static int perf_swevent_get_recursion_context(int **recursion)  { return -1; }
+static void perf_swevent_put_recursion_context(int *recursion)          { }
 
 #endif
 
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);                                   \
                                                                         \
 }