6 files changed, 67 insertions, 24 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index dc61e82faad9..881a94474d79 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -499,6 +499,9 @@ __acquires(kernel_lock)
         else
                 if (!type->flags->opts)
                         type->flags->opts = dummy_tracer_opt;
+        if (!type->wait_pipe)
+                type->wait_pipe = default_wait_pipe;
+
 
 #ifdef CONFIG_FTRACE_STARTUP_TEST
         if (type->selftest && !tracing_selftest_disabled) {
@@ -1064,7 +1067,10 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
         entry->next_prio                = wakee->prio;
         entry->next_state               = wakee->state;
         entry->next_cpu                 = task_cpu(wakee);
-        trace_buffer_unlock_commit(tr, event, flags, pc);
+
+        ring_buffer_unlock_commit(tr->buffer, event);
+        ftrace_trace_stack(tr, flags, 6, pc);
+        ftrace_trace_userstack(tr, flags, pc);
 }
 
 void
@@ -2392,6 +2398,38 @@ tracing_poll_pipe(struct file *filp, poll_table *poll_table)
         }
 }
 
+
+void default_wait_pipe(struct trace_iterator *iter)
+{
+        DEFINE_WAIT(wait);
+
+        prepare_to_wait(&trace_wait, &wait, TASK_INTERRUPTIBLE);
+
+        if (trace_empty(iter))
+                schedule();
+
+        finish_wait(&trace_wait, &wait);
+}
+
+/*
+ * This is a make-shift waitqueue.
+ * A tracer might use this callback on some rare cases:
+ *
+ *  1) the current tracer might hold the runqueue lock when it wakes up
+ *     a reader, hence a deadlock (sched, function, and function graph tracers)
+ *  2) the function tracers, trace all functions, we don't want
+ *     the overhead of calling wake_up and friends
+ *     (and tracing them too)
+ *
+ *     Anyway, this is really very primitive wakeup.
+ */
+void poll_wait_pipe(struct trace_iterator *iter)
+{
+        set_current_state(TASK_INTERRUPTIBLE);
+        /* sleep for 100 msecs, and try again. */
+        schedule_timeout(HZ / 10);
+}
+
 /* Must be called with trace_types_lock mutex held. */
 static int tracing_wait_pipe(struct file *filp)
 {
@@ -2403,30 +2441,14 @@ static int tracing_wait_pipe(struct file *filp)
                         return -EAGAIN;
                 }
 
-                /*
-                 * This is a make-shift waitqueue. The reason we don't use
-                 * an actual wait queue is because:
-                 *  1) we only ever have one waiter
-                 *  2) the tracing, traces all functions, we don't want
-                 *     the overhead of calling wake_up and friends
-                 *     (and tracing them too)
-                 *     Anyway, this is really very primitive wakeup.
-                 */
-                set_current_state(TASK_INTERRUPTIBLE);
-                iter->tr->waiter = current;
-
                 mutex_unlock(&trace_types_lock);
 
-                /* sleep for 100 msecs, and try again. */
-                schedule_timeout(HZ/10);
+                iter->trace->wait_pipe(iter);
 
                 mutex_lock(&trace_types_lock);
 
-                iter->tr->waiter = NULL;
-
-                if (signal_pending(current)) {
+                if (signal_pending(current))
                         return -EINTR;
-                }
 
                 if (iter->trace != current_trace)
                         return 0;
@@ -2442,8 +2464,6 @@ static int tracing_wait_pipe(struct file *filp)
                  */
                 if (!tracer_enabled && iter->pos)
                         break;
-
-                continue;
         }
 
         return 1;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index dbff0207b213..eed732c151fc 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -337,18 +337,34 @@ struct tracer_flags {
 #define TRACER_OPT(s, b)        .name = #s, .bit = b
 
 
-/*
- * A specific tracer, represented by methods that operate on a trace array:
+/**
+ * struct tracer - a specific tracer and its callbacks to interact with debugfs
+ * @name: the name chosen to select it on the available_tracers file
+ * @init: called when one switches to this tracer (echo name > current_tracer)
+ * @reset: called when one switches to another tracer
+ * @start: called when tracing is unpaused (echo 1 > tracing_enabled)
+ * @stop: called when tracing is paused (echo 0 > tracing_enabled)
+ * @open: called when the trace file is opened
+ * @pipe_open: called when the trace_pipe file is opened
+ * @wait_pipe: override how the user waits for traces on trace_pipe
+ * @close: called when the trace file is released
+ * @read: override the default read callback on trace_pipe
+ * @splice_read: override the default splice_read callback on trace_pipe
+ * @selftest: selftest to run on boot (see trace_selftest.c)
+ * @print_headers: override the first lines that describe your columns
+ * @print_line: callback that prints a trace
+ * @set_flag: signals one of your private flags changed (trace_options file)
+ * @flags: your private flags
  */
 struct tracer {
         const char              *name;
-        /* Your tracer should raise a warning if init fails */
         int                     (*init)(struct trace_array *tr);
         void                    (*reset)(struct trace_array *tr);
         void                    (*start)(struct trace_array *tr);
         void                    (*stop)(struct trace_array *tr);
         void                    (*open)(struct trace_iterator *iter);
         void                    (*pipe_open)(struct trace_iterator *iter);
+        void                    (*wait_pipe)(struct trace_iterator *iter);
         void                    (*close)(struct trace_iterator *iter);
         ssize_t                 (*read)(struct trace_iterator *iter,
                                         struct file *filp, char __user *ubuf,
@@ -432,6 +448,9 @@ void tracing_generic_entry_update(struct trace_entry *entry,
                                   unsigned long flags,
                                   int pc);
 
+void default_wait_pipe(struct trace_iterator *iter);
+void poll_wait_pipe(struct trace_iterator *iter);
+
 void ftrace(struct trace_array *tr,
                             struct trace_array_cpu *data,
                             unsigned long ip,
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 4c113a8c466f..c9a0b7df44ff 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -225,6 +225,7 @@ static struct tracer function_trace __read_mostly =
         .init           = function_trace_init,
         .reset          = function_trace_reset,
         .start          = function_trace_start,
+        .wait_pipe      = poll_wait_pipe,
         .flags          = &func_flags,
         .set_flag       = func_set_flag,
 #ifdef CONFIG_FTRACE_SELFTEST
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 519a0cab1530..0ff5cb661900 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -757,6 +757,7 @@ static struct tracer graph_trace __read_mostly = {
         .name           = "function_graph",
         .open           = graph_trace_open,
         .close          = graph_trace_close,
+        .wait_pipe      = poll_wait_pipe,
         .init           = graph_trace_init,
         .reset          = graph_trace_reset,
         .print_line     = print_graph_function,
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index 82fbb5a2df89..77132c2cf3d9 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -221,6 +221,7 @@ static struct tracer sched_switch_trace __read_mostly =
         .reset          = sched_switch_trace_reset,
         .start          = sched_switch_trace_start,
         .stop           = sched_switch_trace_stop,
+        .wait_pipe      = poll_wait_pipe,
 #ifdef CONFIG_FTRACE_SELFTEST
         .selftest    = trace_selftest_startup_sched_switch,
 #endif
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 276c51aaf314..db55f7aaa640 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -380,6 +380,7 @@ static struct tracer wakeup_rt_tracer __read_mostly =
         .reset          = wakeup_tracer_reset,
         .start          = wakeup_tracer_start,
         .stop           = wakeup_tracer_stop,
+        .wait_pipe      = poll_wait_pipe,
         .print_max      = 1,
 #ifdef CONFIG_FTRACE_SELFTEST
         .selftest    = trace_selftest_startup_wakeup,