tracing: Move pipe waiting code out of tracing_read_pipe().

This moves the pipe waiting code from tracing_read_pipe() into
tracing_wait_pipe(), which is useful to implement other fops, like
splice_read.

Signed-off-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

1 files changed, 40 insertions, 29 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9e29fdb0dfe5..11fde0ad9cb6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2388,37 +2388,15 @@ tracing_poll_pipe(struct file *filp, poll_table *poll_table)
         }
 }
 
-/*
- * Consumer reader.
- */
-static ssize_t
-tracing_read_pipe(struct file *filp, char __user *ubuf,
-                  size_t cnt, loff_t *ppos)
+/* Must be called with trace_types_lock mutex held. */
+static int tracing_wait_pipe(struct file *filp)
 {
         struct trace_iterator *iter = filp->private_data;
-        ssize_t sret;
-
-        /* return any leftover data */
-        sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
-        if (sret != -EBUSY)
-                return sret;
-
-        trace_seq_reset(&iter->seq);
 
-        mutex_lock(&trace_types_lock);
-        if (iter->trace->read) {
-                sret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
-                if (sret)
-                        goto out;
-        }
-
-waitagain:
-        sret = 0;
         while (trace_empty(iter)) {
 
                 if ((filp->f_flags & O_NONBLOCK)) {
-                        sret = -EAGAIN;
-                        goto out;
+                        return -EAGAIN;
                 }
 
                 /*
@@ -2443,12 +2421,11 @@ waitagain:
                 iter->tr->waiter = NULL;
 
                 if (signal_pending(current)) {
-                        sret = -EINTR;
-                        goto out;
+                        return -EINTR;
                 }
 
                 if (iter->trace != current_trace)
-                        goto out;
+                        return 0;
 
                 /*
                  * We block until we read something and tracing is disabled.
@@ -2465,9 +2442,43 @@ waitagain:
                 continue;
         }
 
+        return 1;
+}
+
+/*
+ * Consumer reader.
+ */
+static ssize_t
+tracing_read_pipe(struct file *filp, char __user *ubuf,
+                  size_t cnt, loff_t *ppos)
+{
+        struct trace_iterator *iter = filp->private_data;
+        ssize_t sret;
+
+        /* return any leftover data */
+        sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
+        if (sret != -EBUSY)
+                return sret;
+
+        trace_seq_reset(&iter->seq);
+
+        mutex_lock(&trace_types_lock);
+        if (iter->trace->read) {
+                sret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
+                if (sret)
+                        goto out;
+        }
+
+waitagain:
+        sret = tracing_wait_pipe(filp);
+        if (sret <= 0)
+                goto out;
+
         /* stop when tracing is finished */
-        if (trace_empty(iter))
+        if (trace_empty(iter)) {
+                sret = 0;
                 goto out;
+        }
 
         if (cnt >= PAGE_SIZE)
                 cnt = PAGE_SIZE - 1;