tracing: Introduce trace_buffer_{lock_reserve,unlock_commit}

Impact: new API

These new functions do what previously was being open coded, reducing
the number of details ftrace plugin writers have to worry about.

It also standardizes the handling of stacktrace, userstacktrace and
other trace options we may introduce in the future.

With this patch, for instance, the blk tracer (and some others already
in the tree) can use the "userstacktrace" /d/tracing/trace_options
facility.

$ codiff /tmp/vmlinux.before /tmp/vmlinux.after
linux-2.6-tip/kernel/trace/trace.c:
  trace_vprintk              |   -5
  trace_graph_return         |  -22
  trace_graph_entry          |  -26
  trace_function             |  -45
  __ftrace_trace_stack       |  -27
  ftrace_trace_userstack     |  -29
  tracing_sched_switch_trace |  -66
  tracing_stop               |   +1
  trace_seq_to_user          |   -1
  ftrace_trace_special       |  -63
  ftrace_special             |   +1
  tracing_sched_wakeup_trace |  -70
  tracing_reset_online_cpus  |   -1
 13 functions changed, 2 bytes added, 355 bytes removed, diff: -353

linux-2.6-tip/block/blktrace.c:
  __blk_add_trace |  -58
 1 function changed, 58 bytes removed, diff: -58

linux-2.6-tip/kernel/trace/trace.c:
  trace_buffer_lock_reserve  |  +88
  trace_buffer_unlock_commit |  +86
 2 functions changed, 174 bytes added, diff: +174

/tmp/vmlinux.after:
 16 functions changed, 176 bytes added, 413 bytes removed, diff: -237

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Frédéric Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 15 deletions

diff --git a/block/blktrace.c b/block/blktrace.c
index 8e52f24cc8f9..834cd84037b2 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -187,19 +187,15 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
         cpu = raw_smp_processor_id();
 
         if (blk_tr) {
-                struct trace_entry *ent;
                 tracing_record_cmdline(current);
 
-                event = ring_buffer_lock_reserve(blk_tr->buffer,
-                                                 sizeof(*t) + pdu_len);
+                pc = preempt_count();
+                event = trace_buffer_lock_reserve(blk_tr, TRACE_BLK,
+                                                  sizeof(*t) + pdu_len,
+                                                  0, pc);
                 if (!event)
                         return;
-
-                ent = ring_buffer_event_data(event);
-                t = (struct blk_io_trace *)ent;
-                pc = preempt_count();
-                tracing_generic_entry_update(ent, 0, pc);
-                ent->type = TRACE_BLK;
+                t = ring_buffer_event_data(event);
                 goto record_it;
         }
 
@@ -241,12 +237,7 @@ record_it:
                         memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
 
                 if (blk_tr) {
-                        ring_buffer_unlock_commit(blk_tr->buffer, event);
-                        if (pid != 0 &&
-                            !(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC) &&
-                            (trace_flags & TRACE_ITER_STACKTRACE) != 0)
-                                __trace_stack(blk_tr, 0, 5, pc);
-                        trace_wake_up();
+                        trace_buffer_unlock_commit(blk_tr, event, 0, pc);
                         return;
                 }
         }