ftrace: add trace pipe header pluggin

This patch adds a method for open_pipe and open_read to the pluggins
so that they can add a header to the trace pipe call.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 36 insertions, 7 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b9126ef46a9e..32f9106d612c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2307,11 +2307,15 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
         if (!iter)
                 return -ENOMEM;
 
+        mutex_lock(&trace_types_lock);
         iter->tr = &global_trace;
         iter->trace = current_trace;
-
         filp->private_data = iter;
 
+        if (iter->trace->pipe_open)
+                iter->trace->pipe_open(iter);
+        mutex_unlock(&trace_types_lock);
+
         return 0;
 }
 
@@ -2380,13 +2384,24 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
                 return cnt;
         }
 
+        mutex_lock(&trace_types_lock);
+        if (iter->trace->read) {
+                ret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
+                if (ret) {
+                        read = ret;
+                        goto out;
+                }
+        }
+
         trace_seq_reset(&iter->seq);
         start = 0;
 
         while (trace_empty(iter)) {
 
-                if ((filp->f_flags & O_NONBLOCK))
-                        return -EAGAIN;
+                if ((filp->f_flags & O_NONBLOCK)) {
+                        read = -EAGAIN;
+                        goto out;
+                }
 
                 /*
                  * This is a make-shift waitqueue. The reason we don't use
@@ -2400,16 +2415,22 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
                 set_current_state(TASK_INTERRUPTIBLE);
                 iter->tr->waiter = current;
 
+                mutex_unlock(&trace_types_lock);
+
                 /* sleep for one second, and try again. */
                 schedule_timeout(HZ);
 
+                mutex_lock(&trace_types_lock);
+
                 iter->tr->waiter = NULL;
 
-                if (signal_pending(current))
-                        return -EINTR;
+                if (signal_pending(current)) {
+                        read = -EINTR;
+                        goto out;
+                }
 
                 if (iter->trace != current_trace)
-                        return 0;
+                        goto out;
 
                 /*
                  * We block until we read something and tracing is disabled.
@@ -2428,7 +2449,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 
         /* stop when tracing is finished */
         if (trace_empty(iter))
-                return 0;
+                goto out;
 
         if (cnt >= PAGE_SIZE)
                 cnt = PAGE_SIZE - 1;
@@ -2518,6 +2539,9 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
         if (ret)
                 read = -EFAULT;
 
+out:
+        mutex_unlock(&trace_types_lock);
+
         return read;
 }
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index c1ec134ac356..ee53d706066f 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -135,9 +135,13 @@ struct tracer {
         void                    (*init)(struct trace_array *tr);
         void                    (*reset)(struct trace_array *tr);
         void                    (*open)(struct trace_iterator *iter);
+        void                    (*pipe_open)(struct trace_iterator *iter);
         void                    (*close)(struct trace_iterator *iter);
         void                    (*start)(struct trace_iterator *iter);
         void                    (*stop)(struct trace_iterator *iter);
+        ssize_t                 (*read)(struct trace_iterator *iter,
+                                        struct file *filp, char __user *ubuf,
+                                        size_t cnt, loff_t *ppos);
         void                    (*ctrl_update)(struct trace_array *tr);
 #ifdef CONFIG_FTRACE_STARTUP_TEST
         int                     (*selftest)(struct tracer *trace,
@@ -160,6 +164,7 @@ struct trace_seq {
 struct trace_iterator {
         struct trace_array      *tr;
         struct tracer           *trace;
+        void                    *private;
         long                    last_overrun[NR_CPUS];
         long                    overrun[NR_CPUS];