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, 53 insertions, 41 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index eb453a238a6..8fad3776e84 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -776,6 +776,39 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
                 (need_resched() ? TRACE_FLAG_NEED_RESCHED : 0);
 }
 
+struct ring_buffer_event *trace_buffer_lock_reserve(struct trace_array *tr,
+                                                    unsigned char type,
+                                                    unsigned long len,
+                                                    unsigned long flags, int pc)
+{
+        struct ring_buffer_event *event;
+
+        event = ring_buffer_lock_reserve(tr->buffer, len);
+        if (event != NULL) {
+                struct trace_entry *ent = ring_buffer_event_data(event);
+
+                tracing_generic_entry_update(ent, flags, pc);
+                ent->type = type;
+        }
+
+        return event;
+}
+static void ftrace_trace_stack(struct trace_array *tr,
+                               unsigned long flags, int skip, int pc);
+static void ftrace_trace_userstack(struct trace_array *tr,
+                                   unsigned long flags, int pc);
+
+void trace_buffer_unlock_commit(struct trace_array *tr,
+                                struct ring_buffer_event *event,
+                                unsigned long flags, int pc)
+{
+        ring_buffer_unlock_commit(tr->buffer, event);
+
+        ftrace_trace_stack(tr, flags, 6, pc);
+        ftrace_trace_userstack(tr, flags, pc);
+        trace_wake_up();
+}
+
 void
 trace_function(struct trace_array *tr,
                unsigned long ip, unsigned long parent_ip, unsigned long flags,
@@ -788,12 +821,11 @@ trace_function(struct trace_array *tr,
         if (unlikely(local_read(&__get_cpu_var(ftrace_cpu_disabled))))
                 return;
 
-        event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry));
+        event = trace_buffer_lock_reserve(tr, TRACE_FN, sizeof(*entry),
+                                          flags, pc);
         if (!event)
                 return;
         entry   = ring_buffer_event_data(event);
-        tracing_generic_entry_update(&entry->ent, flags, pc);
-        entry->ent.type                 = TRACE_FN;
         entry->ip                       = ip;
         entry->parent_ip                = parent_ip;
         ring_buffer_unlock_commit(tr->buffer, event);
@@ -811,12 +843,11 @@ static void __trace_graph_entry(struct trace_array *tr,
         if (unlikely(local_read(&__get_cpu_var(ftrace_cpu_disabled))))
                 return;
 
-        event = ring_buffer_lock_reserve(global_trace.buffer, sizeof(*entry));
+        event = trace_buffer_lock_reserve(&global_trace, TRACE_GRAPH_ENT,
+                                          sizeof(*entry), flags, pc);
         if (!event)
                 return;
         entry   = ring_buffer_event_data(event);
-        tracing_generic_entry_update(&entry->ent, flags, pc);
-        entry->ent.type                 = TRACE_GRAPH_ENT;
         entry->graph_ent                        = *trace;
         ring_buffer_unlock_commit(global_trace.buffer, event);
 }
@@ -832,12 +863,11 @@ static void __trace_graph_return(struct trace_array *tr,
         if (unlikely(local_read(&__get_cpu_var(ftrace_cpu_disabled))))
                 return;
 
-        event = ring_buffer_lock_reserve(global_trace.buffer, sizeof(*entry));
+        event = trace_buffer_lock_reserve(&global_trace, TRACE_GRAPH_RET,
+                                          sizeof(*entry), flags, pc);
         if (!event)
                 return;
         entry   = ring_buffer_event_data(event);
-        tracing_generic_entry_update(&entry->ent, flags, pc);
-        entry->ent.type                 = TRACE_GRAPH_RET;
         entry->ret                              = *trace;
         ring_buffer_unlock_commit(global_trace.buffer, event);
 }
@@ -861,13 +891,11 @@ static void __ftrace_trace_stack(struct trace_array *tr,
         struct stack_entry *entry;
         struct stack_trace trace;
 
-        event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry));
+        event = trace_buffer_lock_reserve(tr, TRACE_STACK,
+                                          sizeof(*entry), flags, pc);
         if (!event)
                 return;
         entry   = ring_buffer_event_data(event);
-        tracing_generic_entry_update(&entry->ent, flags, pc);
-        entry->ent.type         = TRACE_STACK;
-
         memset(&entry->caller, 0, sizeof(entry->caller));
 
         trace.nr_entries        = 0;
@@ -908,12 +936,11 @@ static void ftrace_trace_userstack(struct trace_array *tr,
         if (!(trace_flags & TRACE_ITER_USERSTACKTRACE))
                 return;
 
-        event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry));
+        event = trace_buffer_lock_reserve(tr, TRACE_USER_STACK,
+                                          sizeof(*entry), flags, pc);
         if (!event)
                 return;
         entry   = ring_buffer_event_data(event);
-        tracing_generic_entry_update(&entry->ent, flags, pc);
-        entry->ent.type         = TRACE_USER_STACK;
 
         memset(&entry->caller, 0, sizeof(entry->caller));
 
@@ -941,20 +968,15 @@ ftrace_trace_special(void *__tr,
         struct trace_array *tr = __tr;
         struct special_entry *entry;
 
-        event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry));
+        event = trace_buffer_lock_reserve(tr, TRACE_SPECIAL,
+                                          sizeof(*entry), 0, pc);
         if (!event)
                 return;
         entry   = ring_buffer_event_data(event);
-        tracing_generic_entry_update(&entry->ent, 0, pc);
-        entry->ent.type                 = TRACE_SPECIAL;
         entry->arg1                     = arg1;
         entry->arg2                     = arg2;
         entry->arg3                     = arg3;
-        ring_buffer_unlock_commit(tr->buffer, event);
-        ftrace_trace_stack(tr, 0, 4, pc);
-        ftrace_trace_userstack(tr, 0, pc);
-
-        trace_wake_up();
+        trace_buffer_unlock_commit(tr, event, 0, pc);
 }
 
 void
@@ -973,12 +995,11 @@ tracing_sched_switch_trace(struct trace_array *tr,
         struct ring_buffer_event *event;
         struct ctx_switch_entry *entry;
 
-        event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry));
+        event = trace_buffer_lock_reserve(tr, TRACE_CTX,
+                                          sizeof(*entry), flags, pc);
         if (!event)
                 return;
         entry   = ring_buffer_event_data(event);
-        tracing_generic_entry_update(&entry->ent, flags, pc);
-        entry->ent.type                 = TRACE_CTX;
         entry->prev_pid                 = prev->pid;
         entry->prev_prio                = prev->prio;
         entry->prev_state               = prev->state;
@@ -986,9 +1007,7 @@ tracing_sched_switch_trace(struct trace_array *tr,
         entry->next_prio                = next->prio;
         entry->next_state               = next->state;
         entry->next_cpu = task_cpu(next);
-        ring_buffer_unlock_commit(tr->buffer, event);
-        ftrace_trace_stack(tr, flags, 5, pc);
-        ftrace_trace_userstack(tr, flags, pc);
+        trace_buffer_unlock_commit(tr, event, flags, pc);
 }
 
 void
@@ -1000,12 +1019,11 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
         struct ring_buffer_event *event;
         struct ctx_switch_entry *entry;
 
-        event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry));
+        event = trace_buffer_lock_reserve(tr, TRACE_WAKE,
+                                          sizeof(*entry), flags, pc);
         if (!event)
                 return;
         entry   = ring_buffer_event_data(event);
-        tracing_generic_entry_update(&entry->ent, flags, pc);
-        entry->ent.type                 = TRACE_WAKE;
         entry->prev_pid                 = curr->pid;
         entry->prev_prio                = curr->prio;
         entry->prev_state               = curr->state;
@@ -1013,11 +1031,7 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
         entry->next_prio                = wakee->prio;
         entry->next_state               = wakee->state;
         entry->next_cpu                 = task_cpu(wakee);
-        ring_buffer_unlock_commit(tr->buffer, event);
-        ftrace_trace_stack(tr, flags, 6, pc);
-        ftrace_trace_userstack(tr, flags, pc);
-
-        trace_wake_up();
+        trace_buffer_unlock_commit(tr, event, flags, pc);
 }
 
 void
@@ -2825,12 +2839,10 @@ int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)
         trace_buf[len] = 0;
 
         size = sizeof(*entry) + len + 1;
-        event = ring_buffer_lock_reserve(tr->buffer, size);
+        event = trace_buffer_lock_reserve(tr, TRACE_PRINT, size, irq_flags, pc);
         if (!event)
                 goto out_unlock;
         entry = ring_buffer_event_data(event);
-        tracing_generic_entry_update(&entry->ent, irq_flags, pc);
-        entry->ent.type                 = TRACE_PRINT;
         entry->ip                       = ip;
         entry->depth                    = depth;